This review uses the following reviews about the fire ecology and management of northern bobwhites as well as primary sources:

• Effects of prescribed burning on games species in the southeastern United States by Maas et al. (2003) [187].
• Northern bobwhite and fire: A review and synthesis by Weber et al. (2022) [321].

Fire-caused Mortality

Direct fire-caused mortality of young and adult northern bobwhites is unlikely during slow-moving fires, because they can move away from flames. However, a few studies document fire-caused injury or death. One study reported that two birds appeared to have been injured by a large, late-winter prescribed fire in tallgrass prairie in Oklahoma [9], and in central Florida, a July prescribed fire in a longleaf pine-saw palmetto community killed a radiotagged adult male that was either “overtaken by the fire or was disoriented by the extreme smoke” [192]. However, in mesquite-redberry juniper communities on the Texas Edwards Plateau, no radiotagged northern bobwhites were killed directly by “relatively cool” January and February prescribed fires. Instead, birds avoided the advancing flames by either moving ahead of or flying over the head fire [35]. Similarly, no mortality was observed during three annual April and May prescribed fires in restored tallgrass prairie on Allwine Prairie Preserve, Nebraska, although two nests were destroyed [75]. Incubating birds become increasingly reluctant to abandon nests over time [15] (see Nesting and Renesting) and disturbances such as fire that occur late in incubation may result in greater vulnerability of adults to fire-caused mortality [192].

Prescribed fire occasionally kills northern bobwhite eggs and destroys nests (e.g., [75,86,156,192,250,309]). For example, in Florida 3 of 139 nests were destroyed following summer prescribed fires over 3 years [192]. In a Nebraska tallgrass prairie, eight northern bobwhite eggs were killed in a May prescribed fire [86] and on Fort Bragg Military Reservation in North Carolina, two nests were destroyed during June and July prescribed fires [250], but no other details were provided.

Northern bobwhite can renest if a nest is destroyed by fire [248], although one study reported little to no postfire renesting following destruction of nests by prescribed fires in June and July [250]. In a review about the effects of fire season birds, Cox and Widener (2008) concluded that northern bobwhites are less likely to renest if a nest is destroyed “very late” in the growing season as compared with early in the growing season [46], although data from specific studies were not provided to support this. In southwestern Florida, renesting probability of northern bobwhites was lower on sites that were burned the previous winter than in unburned sites [248] (see Nesting and Renesting).

Burning may reduce important protective cover for northern bobwhites, and raptor predation on northern bobwhites has been documented during and immediately following January and February prescribed fires [35].

Immediate Fire Effects on Behavior

Northern bobwhites are often found in areas during or soon after fire, although most published information is anecdotal [12,63,79,152,187,283,311]. For example, in northern Florida, northern bobwhites were observed the day after a January prescribed fire and used the burned area until June [311]. In Oklahoma, two coveys were observed in a burned area 2 days after a “hot” 6 August wildfire in prairie-post oak-blackjack oak woodland [12]; however, it is not clear how long the coveys used the burned area.

Some observations suggest that northern bobwhites use recent burns because they are attracted to newly available food resources (e.g., [187,283]), while others describe them leaving burned areas (e.g., [74]). In “Bird Habitat and Fire”, Stoddard (1963) referred to northern bobwhites as "fire birds" because they are attracted to burns before the burned areas “even stop smoking”, filling their crops “in a matter of minutes instead of hours” because dead Insects and seeds are so readily abundant [283]. Other observations suggest that northern bobwhites use burned areas even if food and protective cover are apparently lacking [9,66,132]. In the Texas Panhandle, six northern bobwhites were observed in a pasture 16 days after an early March prescribed fire despite “a complete absence of ground cover and no visible source of food” [132]. In South Texas, northern bobwhites remained in the same area during a prescribed fire and occupied rodent burrows within the fire boundary after the fire even though no suitable vegetation remained (Guthery 2000, cited in [316]). However, Baumgartner (1945) suggested that northern bobwhites may not have been attracted to burns in the tallgrass prairie region of Oklahoma but rather used the burns the day after the fire because they were already there before the fire, noting that within the first 10 postfire days, six of the nine coveys that occurred in the burns on postfire day 1 had moved to either unburned areas within their home ranges, moved to new unburned home ranges bordering the burn, or had disappeared [9]. Other studies describe northern bobwhites leaving areas after burns. For example, in Wisconsin, northern bobwhites as being “evicted” from a burned area the winter following a summer fire due to lack of vegetation cover in the burned area [74]. In Georgia, six of seven coveys on a uniformly burned area altered their previous home ranges to include unburned areas [212]. In Iowa, northern bobwhites did not use burned areas until 35 days after late March and early April prescribed fires [263].

Fire Effects on Habitat, Movement, and Behavior

Summary

A range-wide analysis of northern bobwhite abundance indicated that abundance was generally high the first 7 years after fire then declined, although the relationship between abundance and time since fire varied locally across the range [85]. Examples of how fire affects northern bobwhites in different plant communities are provided in the sections below. Reviews indicate that on mesic and humid sites with high productivity, such as in southeastern pine forests, early successional stages may provide the “best” habitats and frequent, low-severity fire is likely to benefit northern bobwhite, while on xeric and semiarid sites with low productivity, such as in areas of Texas, later successional stages may provide the “best” habitats, and protection from fire for many years may be beneficial [15,215,321] (see Successional Status of Habitats). For example, a fire frequency of 1 to 5 years may be appropriate for northern bobwhite management in southeastern pine forests, while 5 to 10 years may be appropriate in the Great Plains [310]. Because northern bobwhites require foraging habitat that is structurally open up to 0.2 m above ground with protective cover between 0.2 and 1.0 m above ground [15,65,164,282] (see Foraging Habitats and Protective Cover for Refuge and Retreat), a lack of frequent fire on productive sites can result in understory vegetation becoming too dense to allow for northern bobwhite movements and access to food resources [291].

In the short term, fire removes protective cover [187], which can expose northern bobwhites to predation [187,316] and extreme weather [15,114,215], which can reduce populations in the short term if too much protective cover is removed (e.g., [37,182]). Although burned areas may be used despite an apparent lack of protective cover (e.g., [132]) (see Immediate Fire Effects on Behavior), northern bobwhites are more likely to continue to use burned areas if enough protective cover remains [35,163,240,279]. Thus, small and/or patchy fires are likely more beneficial to northern bobwhites than large, uniformly burned areas [187] and low-severity prescribed fires are likely more beneficial than wildfires, which tend to be of higher severity [316] (see Fire Management Considerations: General Recommendations). Burning a large area at one time can be detrimental to northern bobwhite populations, whereas burning many small areas over an extended period (i.e., months rather than weeks) can benefit populations [46].

Fires reduce the amount dead grasses. Because these are used as nesting material, fire may render areas unsuitable for northern bobwhite nesting in the first postfire growing season [57,71,87,110,114,266]. However, burned areas can provide high-quality nesting and brood-rearing habitats after vegetation has recovered [65,119,124,199], and reproductive success can be high after fire, especially after patchy fires that leave nesting cover [33,156,316].

Northern bobwhites use a wide variety of plant and arthropod foods, and their diversity is important for ensuring diet needs are met throughout the year. Northern bobwhites are relatively weak scratchers that need considerable amounts of bare ground to provide direct access to food (see Diet). On productive sites, frequent burning is typically important for maintaining diverse herbaceous plant cover, reducing woody stem density, and maintaining bare ground [321]. Many food items require or are benefited by open canopy conditions and frequent disturbance such as fire [187,195].

Southeastern Pine Forests

Southeastern pine forests are important northern bobwhite habitats, and these include longleaf pine, shortleaf pine, and loblolly pine communities (see Plant Communities and Site Characteristics). These communities are adapted to frequent low-severity fire (see Fire Regimes), and fire is integral to maintain plant structure and composition suitable for northern bobwhites (e.g., [187,253,281]). Noss (2018) described northern bobwhites as “one of the most fire-dependent” birds in the Southeastern Coastal Plain [219], and the northern bobwhite has been described as a “fire bird” in Florida “because they evolved to live in habitat maintained by frequent, low-intensity fire” [22]. Fire exclusion in southeastern pine forests leads to a transition from an understory of grasses, forbs, and sparse hardwood understory to a dense hardwood understory with abundant pine straw, which results in poor habitat for northern bobwhites [321]. In a review of the benefits of prescribed burning in southeastern pine stands for northern bobwhites and other wildlife, Moorman (2002) lists the following:

1. Grasses, legumes, and other herbaceous plants germinate and flower after fire and produce fruits, seeds, and nesting cover.
2. Many shrubs produce more fruit 2 to 5 years after a fire than in unburned areas.
3. Insects and seeds may be more accessible after fire.
4. Plant nutrition and palatability may increase after fire.
5. Vegetation structural diversity—including both herbaceous vegetation and patches of shrubs—may increase after fire [209].

The effects of fire on northern bobwhites and their habitat depend largely on fire frequency, severity, timing, size, and pattern. While frequent, low-severity fire (1–5 years) in southeastern pine forests is often beneficial, large-scale, annual burning may be detrimental (e.g., [163,248,323]). The appropriate frequency of fire in southeastern pine forests depends on site productivity, with slightly longer intervals in less productive Sandhill pine communities than in more productive communities [250]. Ultimately, appropriate fire frequencies depend on the rate of postfire vegetation recovery [250,321] and appropriate fire sizes depend on fire severity, season and pattern [187]. For example, repeated, early growing-season fires in southeastern pine forests tend to favor an understory with greater cover of grasses and forbs, whereas dormant-season fires tend to favor sprouting of woody plants [90,180,187,244,304,321] (see Fire Management Considerations: Southeastern Pine Forests). The actual timing of growing- and dormant-season burns varies by study and location.

Fire Effects on Abundance and Habitat Use

Fire Frequency and Severity

Northern bobwhites occur in both recently burned and in long unburned southeastern pine stands (e.g., [154,155,167,251,277,325]), but abundance is typically highest in recently burned stands [20,21,66,167,203] (see Successional Status of Habitats). For example, northern bobwhite occupancy tended to be lower with longer time since prescribed fire at two sites in mesic longleaf and/or slash pine flatwoods in east-central Florida. On one site, occupancy was greater on plots 1 year since fire (0.22) than on plots 4 years since fire (0.07). On the other site, it was higher on plots 1 year since fire (0.67) than 2 years since fire (0.09). The prescribed fires occurred in both the dormant- and growing-seasons (January–June) and time since fire ranged from 0 to 12 years on the first site and 0 to 2 years on the second site [20]. Similarly, in central Florida dry and mesic pine flatwoods and prairies, northern bobwhites were more abundant around calling points when the area surrounding the points was burned within the previous 2 years than >2 years prior, likely due to improved food on recent burns. The prescribed fires occurred either during the dormant (October–March) or growing (April–September) seasons [203].

In relatively low productivity longleaf pine-scrub oak-threeawn stands at Fort Bragg Military Reservation, northern bobwhites occur in stands with varied fire history [154,155,251], but they are less likely to occur in recently burned areas when they lack protective cover [251]. For example, in one study northern bobwhites selected habitats with their preferred habitat structure regardless of how long it had been since fire (i.e., 1, 2, 3, and ≥4 years) They occurred in areas burned in the dormant season (December–early March) of the current year but avoided areas burned in the growing season of the current year, apparently because the latter lacked sufficient protective cover (see Fire Season) [251]. In another study, northern bobwhites selected areas burned one growing season (1 April–1 October) since low-severity prescribed fire, regardless of burn season. This was likely because the dominant understory grasses—threeawns—flower and set seed the first growing season after fire and provide good habitat structure. They also selected areas ≥3 growing seasons since fire if the fire occurred in the dormant season. This was likely because protective cover provided by sprouting woody shrubs is favored by dormant-season fires. Because northern bobwhites use burned sites with varied fire histories, the researchers recommend that managers incorporate variability into fire prescriptions to create a heterogeneous habitat mosaic [155] (see Fire Management Considerations).

Northern bobwhite populations are often higher in pine stands following restoration treatments that create open-canopied forests with an herbaceous understory than in unrestored stands. Restoration treatments involve thinning and prescribed fire as well as other methods (see Restoration Treatments). For example, in shortleaf pine-oak restoration stands in Arkansas, northern bobwhite abundance is often highest the third growing season after thinning and dormant-season (September–March) fire but it is also high in thinned stands one and two growing seasons after fire [47,197,292,313,330]. Northern bobwhites avoid or show no preference for these stands four, five, and six growing seasons after fire [313]. In Arkansas, northern bobwhite abundance averaged 9.4 times higher in stands the second growing season after midstory thinning and dormant-season (February–March) fire and 19.2 times higher the third growing season after treatments than untreated controls. Abundance was 5.5 times higher in stands the first year after treatments than in controls, but this difference was not statistically significant [47]. Preference for these areas in the first three postfire growing seasons may be because bluestems, the dominant grasses in the understories, remain upright after senescence and provide good nesting and protective cover for northern bobwhites for multiple dormant seasons [155]. In addition, biomass and frequency of occurrence of invertebrates and species richness, density, and frequency of occurrence of food-producing plants increased following treatments [48]. Similarly, in loblolly pine, longleaf pine, and shortleaf pine forests in Mississippi, northern bobwhites were more abundant in forests managed with a 2- to 3- year fire interval and hardwood midstory removal than in forests managed with a 4- to 7-year fire interval and no hardwood midstory removal [334].

Fire Season

The most important nesting months are May through August when one or more peaks in nesting occur (see Reproductive Timing), which coincides with the growing season. In southeastern pine forests, two reviews suggest that population-level effects of growing-season burns are minimal on northern bobwhite populations in southeastern pine forests [16,321] despite the potential for fire-caused mortality of nests during growing-season fires (see Fire-caused Mortality). In pine stands in Tallahassee, Florida, northern bobwhite abundance the first and second fall after burning was slightly greater in an area burned during the previous growing season (May) than an area burned the previous dormant season (February–March) but the third fall after burning abundance was similar between areas. Prior to these fires, both areas had been burned annually in the dormant season (February–March) for 50 years. The researchers concluded that growing-season prescribed fire can be used—at least on a small scale (i.e., these prescribed fires were 200 ha)—without short-term negative impacts on northern bobwhite populations [16]. See below for information about how fire season affects nesting and brood-rearing habitats and reproductive success.

Two studies suggest that northern bobwhites avoid areas burned in the growing season of the current year, likely because of a lack of woody understory important for protective cover. For example, during the breeding season in longleaf pine‐scrub oak sandhill at Fort Bragg Military Reservation, northern bobwhites selected for areas burned in the dormant season (December–March) of the current year but avoided areas burned in the growing season (after mid-March) of the current year [251], and in longleaf pine forest in northern Florida, northern bobwhites were present in plots biennially burned in the dormant season (January–February) during the first postfire breeding season but not in plots burned in the growing season (June–July) [67].

One study found greater mortality rates for adult northern bobwhites in areas burned during the growing-season than areas burned during the dormant-season due to a lack of protective cover in growing-season burns [192], while another study found greater mortality rates in dormant- than growing-season burned areas due in part to better protective cover in growing-season burns [80]. In the first study in pine-saw palmetto flatwoods in southern Florida, adult northern bobwhites that spent most of their time within growing-season (15 April–15 August) burns of the previous year had 1.7 times higher mortality rates than those that spent most of their time in dormant-season (January–15 April) burns of the previous year, a result attributed to growing-season burns reducing woody vegetation cover below suitable levels [192]. In the second study in Alabama, adult and subadult northern bobwhites in longleaf pine forests managed with growing-season (mid-March–early September) burns were 1.5 times more likely to survive each day than those in dormant-season (mid-September–early March) burns, apparently because dormant-season burns had less protective cover and thus greater exposure to predators [80].

One study suggests lengthening the period that burns are conducted within a year to lessen northern bobwhite mortality. In pine plantations in Georgia, adult mortality was lower throughout the breeding season during a year when prescribed burning was conducted from March to June compared to a year when the same number of burns was conducted from March to April. Apparently, the longer burn window enabled the earlier burned areas to recover before the later burns were implemented, providing some protective cover in the area throughout the entire burn window [46].

Fire Size and Pattern

Two studies suggest that northern bobwhites are more abundant in areas with smaller than larger burns [199,323]. However, the size of larger burns in both studies were very small. For example, in the Red Hills, fall northern bobwhite density averaged over 3 years was higher in two 140-ha areas with small burns (about 2 ha; 3.5 birds/ha) than in two 140-ha areas with comparatively large burns (about 8 ha; 2.7 birds/ha) due in part to lower mortality risk in areas with small burns (see below) [323]. Similarly, northern bobwhite densities were consistently higher in a 160-ha area with small burns (10 ha) after thinning and burning treatments than in the same-sized areas with medium (20 ha) and large (40 ha) burns during 3 years [192]. In both studies, the total amount of burned area was similar between the study areas.

One study in south-central Florida indicated that northern bobwhite abundance was highest in areas with greater amounts of area burned within the year. Northern bobwhite abundance was significantly higher at calling points when ≥40% of the 400-m area around them (a.k.a., the buffer area) was burned than when <40% of the area was burned [203].

The effect of burn size and patchiness on northern bobwhite home range size and movements is unclear, and studies of large burns are lacking. A study in southwestern Georgia found that northern bobwhite home ranges were larger on a 190-ha uniformly burned area than a 100-ha patchy burned area during 2 years [212]. In longleaf pine-slash pine communities in southeastern Louisiana, northern bobwhite home ranges averaged 58 ha where vegetation density was sparse due to a recent prescribed burn, but they averaged 18 ha in a nearby area with good protective cover and food [10]. In dry prairie and pine flatwoods in southwestern Florida, northern bobwhites with the largest home ranges (adult mean: 58 ha; juvenile mean: 41 ha) occurred in an areas that was burned the previous January and lacked food and protective cover, while those with the smallest home ranges (adult mean: 18 ha, juvenile mean: 26 ha) had an understory that was relatively dense with both food and protective cover [144]. Together, these studies suggest that individuals using homogeneous burns needed to travel farther to meet resource requirements. However, in the Red Hills, northern bobwhite home ranges were similar between two 140-ha areas with small burns (about 2 ha) and two 140-ha areas with larger burns (about 8 ha) during 3 years [323].

Limited information suggests that adults with young may prefer small burned areas over large burned areas. During the breeding season in South Carolina, adults with and without young preferred small burned areas, with the probability of burn use decreasing as burn size increased within the study area (available burn sizes: 6–243 ha) [199]. In the Red Hills, 10- to 42-day-old juveniles selected sites with greater proportions of burned upland pine forests in an area subjected to small (<20 ha) prescribed fires from March to May at 2-year intervals. Juveniles used burned uplands at similar rates early and late in the breeding season, apparently because of rapid postfire vegetation recovery that provided suitable cover throughout the breeding season [157]. See Fire Effects on Brood-rearing Habitat for more information on that topic.

The effect of burn size and patchiness on northern bobwhite mortality is unclear, but mortality tends to be higher in larger burns or patches than smaller burns or patches. In the Red Hills, the risk of adult mortality during the breeding season was 2.3 times higher in two 140-ha areas with larger burns (about 8 ha) than in two 140-ha areas with small burns (about 2 ha) during 1 of 3 years and there was a trend toward greater mortality risk during the first 60 days of the breeding season during another year. The researchers hypothesized that northern bobwhites were more vulnerable to avian predators in larger burns due to limited proximity of protective cover. Burns were conducted in spring (March–April) such that half of each study area was burned each year [323]. In pine-saw palmetto flatwoods in southern Florida, a model suggested that a 160-ha area with small burns (about 10 ha) had lower mortality rates than the same-sized area with larger burns (about 40 ha) but an area with medium-sized burns (about 20 ha) had the highest mortality rates. The researchers proposed that mammalian predators may be less efficient in searching large burns, while avian predators may be less efficient in searching small burns, while both types of predators were efficient at searching in medium burns [192]. In pine forests interspersed with agricultural fields in southwestern Georgia, mortality of northern bobwhites was greater 30 days after March prescribed fires on a 190-ha uniformly burned area (13.9%–30.3%) than on a 100-ha patchy burned area (7.5%–11.3%) during 2 years. Burned patches ranged in size from 0.2 to 0.8 ha in the patchy burn. Avian predators, especially raptors, accounted for 70% of all mortality during the 2 years, which was especially high in spring during raptor migration. The researchers suggested that avian predation was higher on the larger, uniformly burned area because there was less protective cover [212].

One study found a positive relationship between survival of young northern bobwhites and the proportion of home range area burned. In prairie and pine flatwoods in west-central Florida with a 2- to 3- year fire interval, survival of 3- to 10-day-old northern bobwhites was positively correlated with the proportion of home range area burned during the previous dormant season in two study areas where the size of burned area (mean: 21 and 191 ha) was large relative to home range sizes (mean: 8 and 22 ha). Specifically, the likelihood of daily survival increased 1.8 times with a 45% increase in the proportion of home range area burned [144].

Fire Effects on Nesting Habitat

In southeastern pine forests, northern bobwhites most often nest in 1-year-old [110,266] and 2-year-old [187,250,314] burns (“roughs”), but infrequently nest in relatively long unburned areas (≥3 years since fire) [250,266]. Northern bobwhites use dead plant materials from previous years’ growth almost exclusively to construct nests (see Nest Sites), so northern bobwhites may avoid nesting in areas burned in the preceding dormant season if nesting material is lacking [80,163]. In southwestern Georgia, nest occurrence was highest 1 year after fire in areas burned during spring (i.e., in late March and early April) and then declined with time-since-fire. Twenty-one percent of nests occurred in areas burned the spring immediately prior to the breeding season, 60% occurred in 1-year-old burns, 12% in 2-year-old burns, and 8% in 3-year-old burns [266]. In a slash pine plantation in Georgia, most nests (58% of 76 nests) were located in burned areas that had burned in spring of the same year; 23% were located in 1-year-old roughs; and 19% were located in ≥2-year-old roughs. Dense grass roughs (≥3-year-old) were not used for nesting except at the edges [110]. In longleaf pine‐turkey oak sandhill at Fort Bragg Military Reservation, 16% of 48 nests were in areas burned in April to May of the same year, 19% were in 1-year-old burns, 52% were in 2-year-old burns, and 13% were in ≥3‐year-old burns. Northern bobwhites appeared to prefer to nest in 2-year-old burns because they offered the best combination of herbaceous and woody cover; younger burns (i.e., ≤1 year since fire) lacked substantial woody cover and older burns (i.e., ≥3 years since fire) typically contained taller woody sprouts and matted threeawns that likely restricted movements. Because northern bobwhites primarily nested in 2-year-old burns not scheduled to be burned, few nests (0.75%) were exposed to fire in any given year. A more frequent fire interval, especially during the growing season, would put nests at greater risk [250]. In addition, a shortened fire interval would decrease available nesting cover, especially in regions with low soil fertility such as in the sandhills, where vegetation recovery following fire is less rapid than on more productive soils [250]. In the studies in Georgia, most nests occurred in ≤1-year-old burns [266], suggesting that a 2-year burn interval would pose less risk of nest destruction than at Fort Bragg Military Reservation [250].

Fire Effects on Brood-rearing Habitat

While few studies examined fire effects on brood-rearing habitat, northern bobwhite broods appear to prefer current-year or 1-year-old burns [124,199]. In pine savannas in South Carolina, adults with young used areas burned within the current year (<65 days after low-severity March–May prescribed fires). They were 2.2 times less likely to use areas with a 1- to 2-year fire interval compared to current-year burns, and 2.6 and 2.8 times less likely to use areas with a 2- to 3-year interval and a 3- to 4-year interval, respectively, than current-year burns [199]. In upland pine stands in North Carolina, juveniles from 11 to 82 days old, selected current-year and 1-year-old burns for foraging and current-year burns for roosting based on availability. The researchers noted that while food and protective cover were suitable in current-year burns after the April prescribed fires, they might not be suitable after fires that occur closer to the time of hatching [124].

One study in northern Florida suggested that young may prefer growing-season burns over dormant-season burns but preferred burns during any season over other available habitats. Adults with young from hatch to 42 days old were most often located in pine stands burned during the growing season (49%) but also during the dormant season (39%). Remaining locations were in disked fields (10%) and other habitats (2%). The timing of growing-season and dormant-season burns was not provided [36]. However, in the Red Hills, woody cover was important to young northern bobwhites for roosting and the researchers hypothesized that summer fires that reduce woody plants too much might be detrimental to young. In this study, 10- to 42-day-old juveniles selected roosting habitat with greater amounts of woody cover within a 1-m radius, especially early in the breeding season when herbaceous cover in burns was limited [157].

Fire Effects on Reproductive Success

Few studies examined the effects of fire on northern bobwhite reproductive success in southeastern pine forests, but some studies suggest that recent burns may have greater nest and juvenile survival than unburned areas [80,123]. In longleaf pine forests in Alabama managed with a 3-year fire interval, nest success (the proportion of individuals that survive to the end of the breeding season and hatch at least one egg in a nest in that season) was 1.8 times greater in burned than unburned areas [80]. In longleaf pine-loblolly pine savannas in North Carolina, selection of biannually burned uplands was positively related to mean daily survival of 11- to 77-day-old juveniles [123]. However, in pine and prairie communities in southwestern Florida, hatching success, clutch size, nest survival, and the probability of double nesting and renesting of northern bobwhites were similar between an area burned the previous winter and areas burned less recently than the previous winter [248].

Fire Season

There is some risk of nest destruction during growing-season fires because these fires occur during the breeding season. Fires that occur during peak nesting are especially likely to reduce reproductive success through direct nest losses. Because peak nesting timing varies by location (Fire Effects on Nesting Habitat) the month during which burning occurs is likely to have different effects in different locations [321]. In pine-saw palmetto flatwoods in southern Florida, nest survival of northern bobwhites was higher in areas burned in the dormant season (January–15 April) than in the growing-season (15 April–15 August) due to direct nest losses in growing-season burns, but it was higher in areas burned in either season (2.2 and 1.5 times higher, respectively) than in unburned controls. Early dormant-season burns (January-February) had enough time for vegetation to recover to suitable levels prior to the nesting season in the same year of the fire, while the absence of fire is likely not conducive for nest survival because vegetation becomes too dense [192]. However, in longleaf pine forest in Alabama managed with a 3-year fire interval, nest success did not vary appreciably with time since last prescribed fire (range: 23–2,334 days) or season of last prescribed fire (growing-season versus dormant season) [80].

The length of the nesting season may be shortened by spring burning due to a lack of nesting cover in burned areas, which is likely to reduce reproductive success over the course of the breeding season. In slash pine-longleaf pine plantations in southwestern Georgia, the peak nesting period on areas burned during the current spring (late April-early May) was about a month later than the peak nesting period on unburned areas. The vegetation and litter cover in recently burned areas became suitable for nesting in late June corresponding with increased nesting in burned areas and decreased nesting in unburned areas. Of the 225 nests begun prior to 16 June, 6% were on burned areas (66% of the nesting cover in the study area) and 94% on unburned areas (34% of the nesting cover). Of 160 nests initiated after 15 June, 41% were on burned areas and 59% on unburned areas [266].

Fire Size

The effect of burn size on northern bobwhite reproductive success is unclear. In the Red Hills, northern bobwhite nest production during 3 years was higher in two 140-ha areas with small burns (about 2 ha; 0.68 nests/bird) than in two 140-ha areas with larger burns (about 8 ha; 0.43 nests/bird), likely due to greater adult mortality risk in areas with larger burns (see Fire Size and Pattern); however, nest success (the percentage of nests that had at least one egg hatch) was 1.4 and 1.2 times higher in the areas with larger burns than in the areas with small burns during 2 of the 3 years, perhaps because mammalian predator search efficiency was greater on small burns due to the increased amount of edge available to forage along. Overall, the researchers concluded that burn size would have little impact on overall productivity, and that predation and other factors affecting mortality rates are likely more important [323]; however, burn sizes—even those of larger burns—were small in this study. In pine-saw palmetto flatwoods in southern Florida, northern bobwhite nest survival (the probability of a nest surviving over the incubation period) was higher in a 160-ha area with large burns (40 ha) than in the same-sized areas with small (10 ha) or medium (20 ha) burns, and nest success was higher in the area with large burns (0.59) than in the areas with small (0.50) and medium (0.33) burns. However, an annual productivity index suggested that the area with small burns produced more juveniles per adult female than the same-sized area with large burns. Adult female northern bobwhites likely benefitted from large amounts of habitat created by large burns, but this occurred at a cost of fewer juveniles per adult female per year. Overall, the highest rates of reproduction occurred the year the treatments were applied [192].

Oak and Oak-Pine Communities

Compared with southeastern pine forests, few studies quantify the effects of fire on northern bobwhites and their habitat in hardwood communities. In oak savannas, frequent fire appears to create and maintain suitable habitat for northern bobwhites by maintaining an open understory. In Illinois, northern bobwhites were 10 times more abundant in restored oak savannas that were burned by fall and/or spring prescribed fires at 3- to 5-year intervals and with periodic mechanical removal of mesophytic trees species, especially maples, than in untreated, closed-canopy oak forests [13]. In oak savannas in Indiana, models predicted that northern bobwhite density was maximized at an average fire interval of 3 years by maintaining suitable bare ground conditions [97]. In post oak-shortleaf pine forest in Oklahoma, winter prescribed fire at 1- or 2-year intervals created suitable habitat conditions for northern bobwhites [194].

One study in oak-hickory-pine forests in Georgia and South Carolina suggested that fire likely benefits northern bobwhite populations because of increased habitat heterogeneity. In these communities, early growing-season (mid- to late April) prescribed fires created higher levels of structural diversity and greater length of edge habitat than dormant-season (January–early April) fires or unburned controls [202].

Old Fields

Fire Effects on Abundance and Habitat Use

Generally, the value of old fields, Conservation Reserve Program (CRP) fields, and other mesic grasslands as habitat for northern bobwhites declines with time since fire as dense vegetation, lack of bare ground, and thick litter hinder mobility and foraging in long-unburned grasslands [25,94,245,256]. Moreover, frequent prescribed fire (alone or with other treatments such as grazing, discing, mowing, and/or herbicide application) increases use of mesic grasslands by reducing grass and litter cover; increasing plant diversity; increasing bare ground; and/or reducing woody cover as long as structural diversity and some woody cover remains [88,93,94,96,108,245,256,290]. However, if vegetation cover after fire is too sparse, northern bobwhites may not use burned areas until vegetation structure and cover have recovered to suitable levels [87,263], which can occur the first summer following winter or spring burns [263], but likely depends on weather, plant species composition, and other factors. In grass-shrub habitats in Iowa, the proportion of northern bobwhite observations occurring in areas that burned in late March and early April prescribed fires increased over time from 11% 1 month after fire, 25% 2 months after fire, 43% 3 months after fire, and 59% 4 months after fire, suggesting that the burned area became more suitable as vegetation recovered throughout the summer growing season. The fires killed or top-killed 92% of individual plants of woody species [263]. In restored warm-season CRP grasslands in Kansas, mean northern bobwhite density in plots burned in April and May was lower during each of three breeding season census counts (0.25 birds/km) than in unburned plots (0.43 birds/km) for the first 4 years after fire; although the difference was not statistically significant. Higher densities in unburned plots were attributed to reduced structural heterogeneity of vegetation and reduction in total vegetation cover on burned plots [245].

Once vegetation has recovered, recent burns in old fields and other mesic grasslands appear to be good habitat for northern bobwhites [290] and northern bobwhite abundance is often higher in frequently burned than unburned grasslands [274,290,319]. For example, in Mississippi, northern bobwhite adults with their young selected home ranges with old fields that had been burned and/or disked annually and adjacent woody areas; they avoided unburned old fields [290]. In old fields in Alabama, the fall northern bobwhite population in a burned area was about twice that in an unburned control area during 6 years. The burned area was burned near annually in late winter (February–March) [274]. In North Carolina, the number of northern bobwhites observed per survey was higher in grasslands burned three times in January or February at a 1-year interval (0.15 bird/survey) than in paired untreated control plots (0.09 bird/survey) during 3 postfire years; although the difference was not statistically significant [319].

In general, nonnative tall fescue grasslands are poor habitats for northern bobwhites because they lack suitable vegetation structure, floristic composition, and sufficient access to quality food. Burning and/or disking may improve these grasslands for northern bobwhites but the results are short term [8,93,94,188,189,318]. Conversion of tall fescue grasslands to warm-season grasslands is more likely to provide good habitat for northern bobwhites [304] (see Nonnative Grassland Conversion). For example, in tall fescue grasslands in Mississippi, burning in spring improved habitat for brood-rearing northern bobwhites the first postfire growing season by increasing bare ground cover and reducing litter cover. However, by the second postfire growing season, bare ground and litter cover were similar between burned and unburned control plots, and plant species richness, plant diversity, grass cover, and cover of northern bobwhite food plants did not differ between burned and unburned plots in either the first or second postfire growing seasons. While northern bobwhite brood-rearing habitat was marginally enhanced by structural changes the first postfire growing season, plant community composition was not substantially changed, and structure quickly became less suitable for northern bobwhites over time [94]. In tall fescue grasslands in Kentucky, plant species richness, forb cover, grass cover, bare ground cover, preferred northern bobwhite food plant cover, and invertebrate density and biomass were similar between spring (early March) burned, summer (mid-July) burned, fall (early November) burned, and unburned control plots during the first 2 postfire years, except a few variables differed in some years. In general, burned and unburned plots lacked the vegetation structure to provide good brood-rearing or nesting habitat in one or both years [188,189].

Fire Effects on Nesting Habitat

Fire reduces the amount of suitable nesting material available during the first postfire nesting season [71,87,110,114], so there may be fewer nests until sufficient vegetation has recovered [57,263], especially if the burns are uniform [57]. In bluegrass grassland in Iowa, subjective estimates of nesting cover quality in mid-May generally declined immediately following prescribed fires, then increased in subsequent years until it reached or exceeded prefire or control levels by postfire year 3; trends in renesting cover in late July were similar [87]. In grass-shrub habitat in Iowa, nests were not located in areas burned under prescription in late March and early April because vegetation regeneration was not sufficient for nesting cover until mid-June, after most nests had been initiated. However, 3- to 5-week-old juveniles occurred in burned areas in mid-July [263]. In old fields and pastures in Tennessee, fewer northern bobwhite nests were found in areas burned immediately preceding the nesting season in March than in areas left unburn. The effects of burning varied widely, however, and appeared to depend on the uniformity of the burn and the amount of dead grass available for nest construction. One grassland that burned in a patchy prescribed fire remained suitable for northern bobwhites to nest the nesting season immediately following the fire because some dead grass leaves and stems escaped burning [57].

Because northern bobwhites may avoid nesting in burns until nesting cover is adequate [263], late spring burning may delay nesting and shorten the nesting season [57]. In Tennessee, nesting commenced after 1 June on old fields and pastures burned the March immediately preceding the nesting season, but nesting commenced in mid-April in areas left unburned, apparently due to lack of suitable nesting material. Although nesting began later on burned areas, nesting ceased on both burned and unburned areas at approximately the same time such that the nesting season was compressed in areas burned the March immediately preceding the nesting season. Because clutch size tends to decrease throughout the nesting season (see Nesting and Renesting), a shortened nesting season may reduce the opportunity to renest and lead to lower total reproductive success, despite similar nest success between the two areas [57].

One study suggests that in grasslands where woody cover is limited, fire may reduce northern bobwhite survival by removing too much protective cover. For example, in Kentucky, northern bobwhite survival rates were higher on treated (18%) than control (11%) plots in summer but lower on treated (23%) than control (36%) in winter. The study occurred on reclaimed surface mines planted with native warm-season grasses. Treatments consisted of a combination of disking, February to April prescribed fires, and herbicide application during 4 posttreatment years. Treatment objectives included decreasing cover of nonnative invasive plants (primarily sericea lespedeza), increasing native plant diversity, and increasing woody cover. The researchers speculated that lower winter survival on treated plots may have been due to inadequate shrub cover, especially where treatments resulted in isolated patches within the open matrix, creating larger patches of open vegetation. The patches were preferred during the winter and may have provided thermal and escape cover for northern bobwhites [228].

Tallgrass Prairie

In tallgrass prairies, northern bobwhites require woody cover for protection, which can be sustained using patchy prescribed fires and/or prescribed fires at various intervals. Without this protective cover, survival and abundance are low. For example, in native and restored tallgrass prairies in Missouri, adult northern bobwhite survival was low the first fall and winter after prescribed burning, apparently due to decreased protective cover, which may have forced birds to relocate to unfamiliar or less desirable areas and possibly increased predation [210]. Because northern bobwhites are a “woody-dependent" species in tallgrass prairies, 3 to >4 year fire intervals are more likely to benefit northern bobwhite populations than 1 to 2 year intervals [179,309,340], but fire exclusion leading to dense vegetation and eastern redcedar and other tree establishment is detrimental [239]. In tallgrass prairie in Oklahoma, northern bobwhite density was least in plots <1 year since March to May prescribed fire, intermediate in plots 1 to 2 years since fire, and greatest in plots >2 years since fire. Most plots >2 years since fire were also <4 years since fire [179]. In Kansas, northern bobwhite density was 2.5 times greater on unburned tallgrass prairie with a fire interval >4 years than on annually burned tallgrass prairie that was burned in April [340]. In restored tallgrass prairie in Missouri, northern bobwhite density was lower in plots ≤1 year since fire (0.22 birds/ha) and in plots 2 to 4 years since fire (0.20 birds/ha) than in plots ≥5 years since fire (0.31 birds/ha), but differences were not statistically significant [336]. In tallgrass prairie in Iowa, density of male northern bobwhites was similarly low in plots burned in April and May and unburned plots in postfire year 1 (0.2 males/10 ha on burned plots versus 0.2 males/10 ha on unburned plots), however density was slightly higher in burned than unburned plots in postfire year 2 (0.8 males/10 ha versus 0.7 males/10 ha), and 3.5 times higher in burned than unburned sites in postfire year 3 (1.4 males/10 ha versus 0.4 males/10 ha) [309].

Fall and early winter prescribed fires may leave burned areas without suitable protective cover for long periods. For example, in the tallgrass prairie region of Oklahoma, fall and early winter fires made northern bobwhite ranges uninhabitable during the remainder of the winter due to lack of protective cover, and northern bobwhite coveys shifted use away from burned areas. As vegetation recovered the first spring after fire, coveys shifted back into burned areas. However, covey use of burned areas did not recover to prefire levels until the second fall after fire [9].

In tallgrass prairie, conducting many small burns or a single large, patchy burn is likely to increase landscape heterogeneity such that an area is more likely to contain all habitat attributes that northern bobwhites populations require [91,118,261]. Patch-burn grazing by livestock can increase landscape heterogeneity in tallgrass prairies and other plant communities such as nonnative grasslands by increasing vegetation structural diversity, altering plant species diversity and composition, and reducing woody cover [91,261], and northern bobwhite reproductive rates and juvenile survival may be high in burned and grazed tallgrass prairie as long as suitable protective cover remains. For example, in tallgrass prairie in Missouri, juvenile survival and body condition, adult survival, and reproductive success during the breeding season were greater in landscapes with tallgrass prairie managed with prescribed fire and cattle grazing than in landscapes with agricultural fields and nonnative cool-season grasslands. Most burning occurred at 3-year intervals in winter and spring. No sites were burned during the summer brood-rearing period, so herbaceous and shrub cover were available [268,269,293]. In nonnative buffelgrass-Old World bluestem pastures in the Texas Rio Grande Plains, northern bobwhite density increased in patch burned and cattle-grazed pastures compared with grazed-only pastures. Patch-burn grazing decreased grass standing crop density, increased herbaceous plant species richness, and increased patch heterogeneity in regard to grass standing crop, bare ground, and herbaceous species richness among patches. Patch-burn grazing did not result, however, in measurable increases in northern bobwhite body mass, survival, or reproductive success compared with grazed-only pastures [91].

However, patch-burn grazing appears to have varied results on northern bobwhite abundance. For example, some studies found greater northern bobwhite densities in pastures that were grazed-and-burned every 3 years than in pastures that were only burned every 3 years and in those that were patch-burned-and grazed. Patch-burned-and-grazed pastures consisted of burning one patch within a pasture annually with a fire interval of 3 years for each patch [60,231]. In tallgrass prairie in Oklahoma, northern bobwhite density was similar between patch-burning treatments—in which only portions of each pasture were burned each year to create a mosaic of vegetation patches in various stages of recovery from disturbance—and traditional treatments—in which entire pastures were annually burned. Instead, results indicated that northern bobwhite abundance was positively associated with distance to water bodies and woody edge [43].

Shortgrass and Mixedgrass Prairie

Northern bobwhites need fire intervals long enough for woody cover to recover to moderate levels, and studies in shortgrass and mixedgrass prairies indicate that northern bobwhites are often more abundant on unburned than recently burned prairies, although long-term studies of burn use over time are lacking [182,246]. For example, in shortgrass prairie, relative abundance of northern bobwhites was higher in unburned plots than in plots burned under prescription in winter at 2- or 4-year intervals, a result attributed to the greater protective cover and foraging opportunities provided by large shrubs and pricklypears in the unburned control [182]. In mixedgrass prairie, northern bobwhites were more abundant on unburned sites than on burned sites 1 and 2 years after the 367,000-ha 2006 East Amarillo Complex fires in March [246] that resulted in a high-severity, uniform burn across a large area [246,316]. Another study in the East Amarillo Complex in both shortgrass and mixedgrass prairie found that northern bobwhite density was higher on unburned than burned sites the first breeding season after fire. Density remained higher on unburned than burned sites the second and third breeding seasons, but not significantly. The slow recovery of northern bobwhite populations on burned areas was attributed to slow postfire recovery of woody plants. The authors noted that woody cover in shortgrass prairie is sparser, composed of less fire-tolerant woody species (e.g., lotebush), and therefore likely to recover more slowly than that in mixedgrass prairie dominated by woody species that recover quickly after fire (e.g., Havard oak), so northern bobwhite populations may recover more slowly in shortgrass than mixedgrass prairie but data were not provided [37]. Duration of vegetation recovery following fire also depends on precipitation and soil moisture following fire (Jackson 1965, cited in [316]). For more information about how fire effects northern bobwhites in lotebush and Havard oak communities, see below.

Little information is available regarding northern bobwhite reproduction and nest survival in mixedgrass prairie after fire, but one study indicated that reproduction and survival may be high after patchy fire. Nearly 70% of northern bobwhite clutches survived a June prescribed fire in mixedgrass prairie in North Dakota; 37% eventually hatched and several nests were initiated after the fire. The relatively high survival was attributed in part to areas skipped by the fire as it burned in a mosaic pattern [156]. In mixedgrass-shrubland in Oklahoma, nest survival was examined in four time-since-fire categories: <1 year, 1 to 2 years, 2 to 3 years, and >3 years after dormant-season (January–March) prescribed fires. Nest survival was high (57%–70%) in all time-since-fire categories because suitable nesting cover was available, regardless of time since fire. The type of nesting substrate used, however, varied with time since fire. Up to 1 year after fire, shrubs were the most common nesting substrates (72% of nests), while >3 years after fire, herbaceous vegetation was most common (71%). Shrubs provided similar vegetation structure in young burns as herbaceous plants did in older burns [33]. In mixedgrass prairie burned in the East Amarillo Complex, adult female survival (43%–54%), nest survival (38%–60%), and clutch size (14-16 eggs/clutch) and hatchability (78%–82%) 3 and 4 years after fire were similar to those reported in other studies of mixedgrass and tallgrass prairies despite the complex’s large size and burn uniformity [316].

Texas Rangelands

Texas rangelands with dense woody plants and a sparse herbaceous understory are unsuitable for northern bobwhites. In these areas, northern bobwhites may benefit from patchy fire that creates a mosaic of woody and herbaceous cover and abundant edge habitat [279], but a lack of protective cover after homogeneous fire may result in increased vulnerability of northern bobwhites to predators [240,249,279].

Lotebush-Grasslands

In the Rolling Plains, lotebush thickets in grasslands provide preferred protective cover for northern bobwhites [337]. Lotebush is typically top-killed by fire, and fire may reduce lotebush cover for many years after fire, resulting in a loss of protective cover if all plants are burned [240,249,279]. For example, in a lotebush-mesquite/tobosa community the Rolling Plains, the year of the fire, northern bobwhites did not use an area burned in a “hot” April prescribed fire where all lotebushes were burned but used an area burned in a “cool” burn the following year that left sufficient lotebushes unburned. Five to 6 years after the fires, northern bobwhites in burned areas selected lotebushes that were larger than those available. These lotebushes had either escaped fire or were partially defoliated. Lotebushes with a volume of about 1 m3 were considered the smallest to be useful to northern bobwhites. Top-killed lotebushes recovered slowly and in postfire year 6, had recovered to only about 70% of their unburned volume; only the largest of these were used by northern bobwhites. [240]. Because lotebush may take 6 to 10 years to again become useful to northern bobwhites as protective cover, fire more frequent than this would be likely to eliminate important cover unless individual lotebush plants are protected during fire. Burning when soil moisture is relatively high may reduce damage to lotebush and other plants that provide protective cover [321]. For more information about fire ecology of lotebush, see the FEIS Species Review about lotebush.

Mesquite-Grasslands

Mesquite grasslands provide important habitat for northern bobwhites but areas with dense mesquite cover and little bare ground are not good habitats. Prescribed fires are used to reduce dense woody cover and increase bare ground to suitable levels for northern bobwhites in mesquite communities (e.g., [183,254,331,332]). However, mesquite may recover to prefire values within a few years after low-severity fire that top-kills plants (see the FEIS Species Reviews about honey mesquite and velvet mesquite), and rapid postfire vegetation recovery and reduction of bare ground over time may make repeated fire necessary to maintain suitable habitat. For example, in huisache-mesquite grasslands in South Texas, northern bobwhite density declined between the first (2.5 individuals/km), second (1.1 individuals/km), and third (0 individuals/km) posttreatment winters following a summer prescribed fire intended to reduce woody cover. The decline in northern bobwhite density on the burned site over time was attributed to a decline in bare ground [183]. In chaparral-grassland in South Texas, northern bobwhite density was higher during the first year after fire in areas burned by December prescribed fires than in an unburned area. However, by postfire year 2, density was similar between burned and unburned areas. The decline in northern bobwhite density in the burned areas after 2 years was attributed to the decrease in bare ground and comparable vegetative composition between burned and unburned control areas [331]. In honey mesquite-hackberry pastures in the South Texas Rio Grande Plains, woody plant density and cover were lower on sites that received two dormant-season (November–March) prescribed fires 2 years apart (22% woody cover) and sites that received a combination of one dormant-season fire followed by one August fire (26%), than on untreated sites (44%). These results suggest that repeated prescribed fire could be used to reduce woody cover to suitable levels for northern bobwhites regardless of season [254]. In rotationally grazed honey mesquite-blackbrush acacia-algerita chaparral-mixed grassland, northern bobwhites were denser on burned areas the spring following December prescribed fires than in an unburned area. However, northern bobwhite density decreased from the first postfire spring to the second postfire spring coincident with a decline in bare ground [332].

A combination of prescribed fire and other treatments can improve northern bobwhite habitat in mesquite grasslands if enough woody cover remains after fire, but habitat quality may decline over time as bare ground decreases. In mesquite-blackbrush acacia communities in the Texas Rio Grande Plain, northern bobwhite abundance was higher 2 and 3 years after plots were treated with herbicide to reduce woody cover then burned in spring than in untreated control plots. Treated and untreated plots had 26% and 88% woody cover, respectively. Northern bobwhites apparently benefitted from increased herbaceous cover after fire because sufficient woody cover remained after fire (Steuter 1978, cited in [279]). In huisache-mesquite pastures in South Texas, northern bobwhite abundance declined between the first and third posttreatment winters on plots treated with summer prescribed fire (from 2.5 to 0 birds/km) and on plots treated with roller chopping, summer prescribed fire, and herbicide applications to reduce woody cover (from 2.0 to 0 birds/km). Northern bobwhites were never detected on untreated control sites. The decline in northern bobwhite density on both treatment types over time was attributed to a decline in bare ground [183].

Northern bobwhites may not use burned mesquite communities if woody and/or herbaceous cover is too low after fire due to drought or other factors. In mixed thorn scrub on the Edwards Plateau and South Texas Coastal Plains, northern bobwhite density was similarly low in areas burned by a patchy prescribed fire in September (2005) and in unburned areas the first growing season after fire, a result attributed to drought that resulted in similarly low herbaceous cover on burned and unburned areas [42]. In mesquite communities on the Texas Rolling Plains, northern bobwhite densities were similarly low on February-burned plots 2 to 8 years after fire and unburned control plots, a result attributed to low shrub cover on both burned and unburned plots [234]. In mesquite-redberry juniper communities on the Texas Edwards Plateau, northern bobwhites used unburned islands of vegetation as refuge areas in burns 6 months after “cool” prescribed fires in January and February; if no islands were available, they moved off the burned areas [35].

While fire may reduce nesting cover and increase nest vulnerability to predators [35,115,119], northern bobwhite reproductive success may not be affected if nesting cover is available after fire. On the Texas Edwards Plateau, nest initiation and success and adult survival was similar between burned and unburned mesquite-redberry juniper communities 6 months after “cool” prescribed fires in January and February that left patches of unburned vegetation. Nest initiation and success occurred mostly in association with pricklypears, especially on burned sites [35]. Northern bobwhite nest success and adult survival did not differ between treated and untreated pastures 2 to 3 years after treatment in a honey mesquite savanna in the Texas Rolling Plains and Cross Timbers and Prairies ecoregions. Treatments consisted of February prescribed fires followed by herbicide application that reduced pricklypear densities. Although pricklypears are important as nest sites, bunchgrass density was adequate in both treated and untreated areas to provide high-quality northern bobwhite nest sites and protective cover on both sites [119]. In contrast, nesting cover was similarly low in burned plots the first growing season after a patchy September prescribed fire and in unburned plots in mixed thorn scrub on the Edwards Plateau and South Texas Coastal Plains due to drought. Predation rates on artificial northern bobwhite nests was high in both burned and unburned areas due to the very low protective cover [42]. On the Texas Rolling Plains, a nest built about 3 weeks after a prescribed fire in burnt pricklypear was depredated before the female finished laying. The prescribed fire had almost uniformly "scorched" the pasture, leaving little vegetation and much open ground [115].

While fire may improve habitat conditions in mesquite communities, it may alter the growth form of mesquite, making them less suitable to northern bobwhites. On the Texas Rolling Plains, mesquite trees used by northern bobwhites tended to be large (≈50 m3). Low-growing, multiple-stemmed resprouts were rarely used as loafing cover when larger trees were available [240].

Havard Oak Communities

Havard oak resprouts after top-kill by fire, and Havard oak shrublands exhibit rapid structural recovery following fire [316,321]. Prescribed fire in these shrublands may maintain suitable amounts of woody cover and increase habitat heterogeneity preferred by northern bobwhites [32,178]. For example, in Oklahoma, the greatest relative abundance of northern bobwhites during the breeding season occurred in recently burned (<1 year since fire) Havard oak shrublands compared with shrublands burned 1 to 2, 2 to 3, or >3 years prior, a result attributed to increased heterogeneity of vegetation structure and composition. Relative abundance was least in shrublands burned >3 years since fire. Shrublands were mostly burned under prescription January to March but also July to August [178]. Another study found home ranges of northern bobwhite coveys were smaller for coveys using 2- to 3-year-old burns than in burns <1 year, 1 to 2 years, and >3 years since fire. The researchers noted that recovery of Havard oak to prefire structure occurs between 2 and 3 years after fire, and smaller home ranges during this period suggests that northern bobwhites benefit most during this period [32]. For more information about the fire ecology of Havard oak, see the FEIS Species Review for Havard oak.

Juniper Communities

As long as sufficient protective cover remains after fire, fire may produce good quality northern bobwhite habitat in redberry juniper communities by removing litter, killing or top-killing dense redberry junipers, and increasing the abundance of other shrubs, forbs, and grasses [173,174,338]. In redberry juniper pastures on the Texas Rolling Plains, woody canopy cover and northern bobwhite densities during the breeding season were highest in an unburned area (22% woody cover and 60.5 birds/100 ha), intermediate in an 8-year-old burned area (14% and 55.1 birds/100 ha), and lowest in a 4-year-old burn area (9% and 43.3 birds/100 ha). While northern bobwhite density was lowest in the 4-year-old burn, adult northern bobwhites had better body condition, likely because this burn had the greatest amount of prairie broomweed—seeds of which are an important food for northern bobwhites [173,174]. For more information about fire ecology of redberry juniper, see the FEIS Species Review about redberry juniper. See Mesquite/Grasslands for information on survival and reproduction in mesquite-redberry juniper communities.

Unlike redberry juniper, Ashe’s juniper does not resprout, so fire may reduce protective cover for longer periods in these plant communities. However, a northern bobwhite population appeared to be “unaffected by burning” in an Ashe’s juniper community near Cross Plains, Texas, that had been bulldozed 5 years prior to reduce Ashe’s juniper cover. The researchers concluded that a fire every 20 to 30 years would be adequate to maintain Ashe’s juniper and grass cover at suitable levels [337]. For the FEIS Species Review about Ashe’s juniper for more information.

Sand Sagebrush Steppe

In sand sagebrush steppe where sand sagebrush is sparse to moderately dense, uniform burns are likely to reduce northern bobwhite habitat until sand sagebrush recovers. However, sand sagebrush resprouts and structure recovers rapidly following fire. Plant height, canopy area, and canopy volume can return to preburn conditions within 4 years [321]. In sand sagebrush steppe in western Oklahoma, northern bobwhite density was similar in pastures managed with patch-burn grazing that had burned patches ranging from recently burned to ≥3 years since fire, and unburned, grazed pastures. In this study, sand sagebrush recovered within 2 to 3 years after fire and both patch-burned and unburned pastures had sufficient woody cover for northern bobwhite habitat suitability [125]. For more information about the fire ecology of sand sagebrush, see the FEIS Species Review about sand sagebrush.

Fire Effects on Food

Fire Effects on Food Accessibility

Northern bobwhites are relatively weak ground scratchers and cannot forage in dense litter or dead herbaceous vegetation, so bare ground is important at foraging sites [150,282] (see Diet and Foraging). Fire reduces litter and increases bare ground, exposing seeds and burned insects, making them accessible to northern bobwhites [150,163]. Dense litter accumulations also compete with and smother herbaceous understory vegetation important to northern bobwhites [282]. Fire may also improve foraging sites for northern bobwhites by reducing the height of herbaceous vegetation and concentrating insects closer to the ground where they can access them (i.e., within 15 to 20 cm from the ground). For example, on reclaimed surface mines in West Virginia, foraging rates of ≤3-week-old juveniles from two broods were highest in burned plots and lowest in unburned plots. The highest foraging rate for one of the broods was obtained on a burned plot where vegetation averaged 14.8 cm tall, while the lowest foraging rates were recorded on unburned plots where vegetation height averaged 28.7 cm and 59.6 cm, far out of reach of the birds [19]. In loblolly pine forests in Louisiana, 11- to 14-day-old juveniles were more successful at capturing arthropods, and arthropod abundance was greater in forests managed using prescribed fire followed by herbicide application to reduce understory woody cover compared with untreated control plots. They were also more successful at capturing arthropods in burned-only plots than untreated plots, but arthropod abundance was lower in burned-only plots than untreated plots [27].

Fire Effects on Food Abundance

Plants

Seeds are an important part of the diet of northern bobwhite, including the hard masts (e.g., acorns) and soft masts (fruits) of trees and shrubs, seeds of leguminous forbs and shrubs, and seeds of other forbs and grasses. A diversity of food plants increases the likelihood that some food resources will be available year-round [238] (see Diet). Fire has different effects on different plants and effects depend on fire season, severity, and frequency, among other factors.

A 2003 review of the effects of prescribed burning on game species in the southeastern United States concluded that the abundance of northern bobwhite food plants typically increases after fire but depends on plant species and fire characteristics (e.g., frequency and season) [187]. While annually burned areas may provide abundant food plants in southeastern pine forests [23,187], in general, access to habitats with a range of fire histories and fire timings are important to provide a diverse diet consisting of both herbaceous and woody plant species [23,166,201,282]. For example, in southeastern pine forests, northern bobwhites benefit from a combination of habitats in close proximity comprised of 1) annually burned herbaceous areas for grass and forb seed production, 2) 2- to 3-year-old roughs for soft mast and nesting and protective cover, and 3) hardwood coverts (areas unburned for 4 or more years) for hard mast production [201]. In a longleaf pine forest in Georgia, legume, grass, spurge, and total plant density were highest in annually burned plots (1 growing season since burning in March), intermediate in 2-year roughs (2 growing seasons since burning in March), and lowest in 3-year roughs (3 growing seasons since burning in March). However, the 3-year rough provided the greatest seed and plant diversity because it contained herbaceous species that had peaked in abundance earlier, plus the woody vegetation succeeding them [23]. In longleaf pine forests in Louisiana, the number of stems of northern bobwhite food plants was highest in 1-year-old burns (100 stems/100 m2) then declined to 70 stems/100 m2 in 2-year-old burns, 43 stems/100 m2 in 3-year-old burns, and 51 stems/100 m2 in 4-year-old burns [237]. While spring burning can provide abundant herbaceous foods in southeastern pine forests, burning at other times of year may also result in abundant foods. For example, in South Carolina total annual seed production of legumes averaged 0.46 kg/ha on summer-burned plots, 0.35 kg/ha on spring-burned plots, and 0.07 kg/ha on unburned control plots [51].

Seeds and fruits of trees and shrubs are important northern bobwhite foods in many areas. For example, they comprised more than 50% of the northern bobwhite’s diet during 8 to 10 months in pine forests in northern Florida [201]. The effects of fire depend on the species, site characteristics, and fire characteristics [187], but seeds and fruits of trees and shrubs are usually reduced the first growing season after fire [139,165,187,201,282]. For example, in slash pine plantations in Georgia, total fruit and seed production of shrubs was least the first postfire growing season (April–October, 0 g/100 m2). It increased to 341 g/100 m2 the second postfire growing season, peaked in the third postfire growing season (448 g/100 m2), and declined to 197 g/m2 the fourth postfire growing season [139]. In upland longleaf pine forests in North Carolina, 0% of fruit detected was produced the same year as the fire, 6% in postfire year 1, and 94% in postfire year 2 [165]. In southeastern forests, seeds of pines, such as longleaf pine and slash pine, can make up more than 70% of the winter diet by volume during a given year and acorns can make up more than 65% [238]. In Tampa, Florida, longleaf pine produced more cones in plots burned at 1-, 2-, and 5-year intervals than those in plots burned at 7-year intervals or in unburned plots. All burns occurred from mid-May to early August [111]. In South Florida slash pine, newly resprouted ramets of white oaks (Chapman oak and sand live oak) produced acorns during the first year following a May prescribed fire, whereas red oaks required 3 years (myrtle oak) or 4 years (turkey oak) to produce acorns [2]. Because trees and shrubs produce seeds and fruits at different times during the growing season, having a diversity of tree and shrub species after fire increases the likelihood that seeds and fruits are available to northern bobwhites over much of the year [187]. Harlow and Lear (1989) provide a list of trees and shrubs in the southern Appalachian Mountains, the seasonal availability of their seeds and fruits, and effects of fire [106].

On Texas rangelands, fire may also increase the abundance of herbaceous plants that are important to northern bobwhites [255], although results depend on site and fire characteristics (e.g., [105]), and increases may be short lived [149]. For example, in mesquite-spiny hackberry communities in the South Texas Plains, forb diversity was similar, but forb cover, density, and frequency were greater in plots 2 to 5 months after January to March prescribed fires than unburned plots. Specifically, cover of prairie sunflower, croton, and whitemouth dayflower—forbs important to northern bobwhites—was greater on burned sites 2 to 5 months after fire than unburned sites [255]. In Pan American balsamscale grassland in South Texas, total biomass of seeds from grasses and forbs in a pasture burned in January was consistently higher than in an unburned pasture each month following, from April to October. However, the following year, total seed biomass was similar between burned and unburned pastures each month, except in August when it was lower [149]. On sandy and clay sites in South Texas, forb yields in June were higher in plots burned in December than in plots burned in January and February, while grass yields were higher in plots burned in January and February than in December. Forb and grass responses to burn month were attributed to plant phenology. The cool-season forbs germinated or initiated growth before most of the warm-season grasses. Thus, fires later in the dormant season reduced forb production but enhanced grass production. December burns, in contrast, were conducted before most forbs had initiated growth [105].

For more information on the effects of fire on northern bobwhite food plants, see these literature reviews: [159,187,262,282]. See also FEIS Species Reviews about individual species.

Arthropods

Northern bobwhites eat arthropods, especially insects, primarily by foraging for them on the ground or gleaning them from plants (see Diet). Insect populations may increase, decrease, or remain unchanged following fire, and responses of the overall insect community to fire are complex. In the short-term, fire may reduce insect abundance through direct mortality and reduction of plants required for food, shelter, and oviposition sites, or increase abundance by attracting pyrophilous insects to freshly burned areas. Insect abundance then generally increases as regrowth of plants attracts recolonizing insects. The effect of burning on insect diversity and abundance over the long term varies considerably depending in part on insect taxa (e.g., its mobility and feeding guild) and life history stage; fire frequency, severity, size, and timing; plant community; and other disturbances (e.g., [11,31,153,217,227,235,284,315]). A literature review of fire effects on arthropods in the Great Plains found that insects in the orders Coleoptera and Orthoptera tended increase abundance after fire in the short term, while insects in the orders Lepidoptera and certain suborders of Hemiptera as well as arthropods in the order Araneae tended to decrease abundance. They also note that long-term studies are needed. Insects in the orders Diptera, Hymenoptera, and Hemiptera, overall, showed variable responses to fire with no clear positive, negative, or neutral pattern [153].

Some studies that examined arthropod abundance as it relates to northern bobwhite habitat management found that fire can have an overall positive effect on total arthropod abundance and biomass during the first postfire breeding season that may improve brood-rearing habitat (e.g., [128,236]). Others found negative or no effect of fire on arthropod abundance and biomass, but potentially improved access to them [42,96,149,188,273]. For example, in a 5-year-old transmission line right-of-way in Mississippi, arthropod density and biomass were greater on burned sites 5 to 7 months after a February prescribed fire than on unburned sites [128]. In mixedgrass prairie of Oklahoma, burned sites had greater abundance and biomass of arthropods than unburned sites 2 to 5 months after fire, and burned sites had lower vertical vegetation structure, shrub cover, and litter cover and more bare ground than unburned sites, suggesting that burning created favorable habitat characteristics and more prey for northern bobwhites the first breeding season after fire [236]. In Pan American balsamscale-mesquite grassland South Texas, there were no significant differences in total invertebrate density between burned and unburned pastures either the first or second breeding seasons after fire, although burning had differing effects on specific orders. However, invertebrates became more accessible to northern bobwhites with shorter and more open vegetation canopy following burning [149]. In restored native warm-season grasslands in Tennessee, abundance and biomass of invertebrates were similar between burned plots and unburned control plots and appeared to be sufficient for young northern bobwhites in both [96].

In southeastern pine forests, frequent fire appears to increase overall arthropod species richness (total number of species), beta diversity (variation in species between sites) [54,89,264], density [233], and biomass [16,233]. However, some studies found that most arthropod types were more abundant or as abundant in 3-year-old roughs than in annually burned plots [61,129]. Regardless of abundance, arthropods are likely more available in annually burned plots than in roughs because dense litter prohibits access to them [129,187]. Because juveniles require areas with woody plants for protective cover [157], they may not use areas without such cover, regardless of insect abundance or accessibility [129] (see Southeastern Pine Forests: Fire Effects on Brood-rearing Habitat).

Growing-season fire in southeastern pine forests may have a short-term negative impact on invertebrate abundance and biomass but may increase invertebrate abundance and biomass in the long term [320]. For example, in a relatively undisturbed longleaf pine-threeawn community in Georgia, total invertebrate abundance and biomass was less during the first postfire breeding season (April–September 1996) in plots burned in May than in plots burned in July or December or unburned plots. However, during the second postfire breeding season (1997), May-burned plots had greater abundance and biomass than any other plots [320].

Fire Effects on Predation

Mammals and Birds

Fire removes protective cover for northern bobwhites and potentially exposes them to increased predation, at least in the short term [159,192]. For example, in Mississippi, burning and/or disking annually increased habitat suitability of broomsedge bluestem old fields such that northern bobwhite populations increased during the first 3 treatment years, then declined, a result attributed to increasing mortality due to increased mammalian predation. Apparently, the treated sites were also attractive to mammalian predators [289,290]. Reviews concluded that high predation levels are also likely when late winter burning is conducted over large areas where few, if any, patches of protective cover remain [159,187] (see Fire Effects on Habitat, Abundance, and Reproduction).

Fire Ants

In the southern United States, the nonnative invasive red imported fire ant has been implicated in northern bobwhite population declines [5,215]. Red imported fire ants can reduce nest survival rates, reduce juvenile biomass and survival, and alter juvenile behavior [5], especially in areas with high densities of multiple-queen colonies because these colonies reach much higher densities than single-queen colonies [5,100,215]. In Ontario, the European fire ant may pose a similar threat to northern bobwhite populations [71].

Red imported fire ant mound (nest) density is positively associated with frequently disturbed habitats (e.g., [299]); however, prescribed fire has not been shown to affect red imported fire ant abundance. In the Texas Coastal Prairie, red imported fire ant mound density was the same in plots burned under prescription in February and March and control plots 5 months and 16 months after treatments [81,82]. In three other counties in the Texas Coastal Prairie during 2 years, the mean number of foraging red imported fire ants in plots burned in January to March prescribed fires was similar to that in unburned plots up to 12 weeks after fire. Insecticide was effective at reducing the number of foraging red imported fire ants compared with untreated plots, but burning combined with insecticide application provided no additional benefit to insecticide application alone [218].

Fire Regimes

Northern bobwhites occur in a variety of plant communities in the eastern and central United States (see Plant Communities and Site Characteristics) that historically had varied fuel structures and fire regimes, but they are most common in ecosystems that experienced relatively frequent fire historically. For example, historical fire frequency estimates based on LANDFIRE succession modeling range from 2 to 11 years in southeastern pine forests (longleaf pine, loblolly pine, shortleaf pine, slash pine, and pond pine); to 13 to 26 years in mesquite scrub, shrubland, and woodland; to 2 to 24 years in shortgrass, mixedgrass, and tallgrass prairies [162]. For additional fire regime information, search FEIS for this species by entering the species name or acronym on the home page and selecting “Fire Regime” as the publication type.

Tree ring and fire scar data indicate that some regions where northern bobwhites occur historically had proportionately more growing-season fires, some had more dormant-season fires, and others had a mix of the two. Differences have been attributed to differences in the relative contributions of human-caused versus lightning-caused fires [89]. In southeastern pine forests, fires were most common historically during the growing season (March–October). Within this period, lightning-ignited fires were most common from May to August, peaking during the transition between the dry and wet seasons (May–June). Dormant-season (September–March) fires were also common, likely due to American Indian burning [70,148,321]. Fires were predominately of low severity [162]. In mesquite ecosystems in Texas, fires were most common during the dormant season (fall–spring) and late summer, depending on location [276]. Fires were predominantly of replacement severity [162]. In prairie ecosystems of the Great Plains, most lightning-caused fires occurred during the late summer dry season and American Indian burning was concentrated in spring and fall [198]. Fires were predominantly of replacement severity [162].

Fire suppression and exclusion in the early 20th century created conditions unsuitable for northern bobwhites throughout their range. For example, lack of fire or other disturbance in southeastern pine forests promoted a dense undergrowth of shrubs and small hardwoods below the pine canopy, resulting in a loss of food resources and protective cover and contributing to northern bobwhite population declines. Timber harvest and planting have also converted forests from open stands of fire-resistant longleaf pine and shortleaf pine to dense stands of relatively less fire-resistant loblolly pine, changing the forests’ response to fires when they do occur. Prescribed fire can be difficult to accomplish in southern pine forests with a legacy of fire exclusion due to high fuel accumulations [89,191,229,307] (see Restoration Treatments). It was not until the 1940s and 1950s that prescribed burning for fuel reduction gained general acceptance. Since then, prescribed fire has been a common management strategy to promote northern bobwhite populations in southeastern pine forests [321]. In the southern Great Plains, fire suppression and heavy livestock grazing resulted in less frequent fire and establishment and spread of mesquite and eastern redcedar [6,65].

In semiarid regions, nonnative invasive species may make fire more frequent than it was historically. For example, buffelgrass establishment may promote a grass/fire cycle that reduces native plant cover important to northern bobwhites and further exacerbates buffelgrass dominance and invasion [91]. See the FEIS Species Review about buffelgrass for more information on how this species might alter fire regimes in invaded communities. See Nonnative Invasive Species Management for more information about nonnative invasive species threatening northern bobwhite populations.

Fire Management Considerations

General Recommendations

Northern bobwhites occur in a variety of ecosystems but are most common in ecosystems that experienced frequent fire historically and many endemic plant species in these ecosystems are fire dependent [304,321] (see Fire Regimes). Thus, managing northern bobwhite habitats with prescribed fire is a common management practice, particularly in southeastern pine forests [253,304]. Such management practices benefit other bird species with similar habitat requirements. For example, in southeastern pine forests management practices for northern bobwhites and endangered red-cockaded woodpeckers are complementary and benefit many other high-priority bird species, including Bachman’s sparrows, Henslow’s sparrows, and prairie warblers [196,215] (see Fire Management Considerations: Southeastern Pine Forests). Management practices for northern bobwhites also overlap substantially with the habitat requirements for the gopher tortoise [196]. For these reasons, northern bobwhites are sometimes described as an “umbrella species” for other species that inhabit open plant communities within their distribution (e.g., [50]).

Benefits of fire to northern bobwhites in different plant communities include:

• Setting back plant succession (see Successional Status of Habitats)
• Reducing litter and increasing bare ground (see Fire Effects on Food Accessibility)
• Increasing ease of mobility (see Foraging Habitats)
• Increasing plant and insect food abundance (see Fire Effects on Food Abundance)
• Increasing heterogeneity of vegetation structure and composition (see Habitat Composition)
• Altering woody plant density and cover (see Protective Cover for Refuge and Retreat)
• Controlling nonnative invasive plants and other undesirable vegetation (see Nonnative Invasive Species Management) [64,163,213,230,301,321]

Because different habitat components respond differently to fire than others, Colter (2009) stated that tradeoffs exist between habitats that provide food, protective cover, and nest sites for northern bobwhites, and it is difficult to manage for all the necessary habitat components simultaneously, noting that no single treatment in her study was able to maximize habitat conditions for northern bobwhites in time and space due to differences in habitat use within and among seasons [40].

Specific management recommendations for northern bobwhites are based on multiple factors, including past land use, soil fertility and site productivity, and disturbance history, along with management goals, objectives, and available resources [15]. However, recommendations to create and maintain viable northern bobwhite habitat all have the same goal: high habitat diversity distributed in a mosaic pattern [187]. Pyrodiversity across the landscape—the method of using fire to promote a heterogeneous landscape by varying fire regime characteristics, including frequency, season, application method, and fire weather conditions [264]—is likely to benefit northern bobwhites by facilitating heterogeneity in plant communities and thus food and protective cover [30,264,321]. A review of prescribed fire effects on wildlife in slash pine ecosystems concluded that variations in fire size, season, and interval creates a mosaic of successional stages that tend to favor northern bobwhites as well as the greatest diversity of animal species [180]. While local conditions dictate the optimal fire timing and scale that results in the most suitable habitat for northern bobwhites [321], in general, large fires and uniform burns create poor habitat conditions. Patchy fires with a variety of severities are most desirable for northern bobwhites because they provide the greatest variety of plant successional stages and greatest amount of edge habitat [163]. Other management practices (e.g., herbicide, livestock grazing, mechanical treatments, and/or reseeding) can be integrated with fire when appropriate to achieve desired vegetation conditions as prescribed fire alone may not be sufficient to achieve substantial long-term shifts in vegetation composition and structure favorable to northern bobwhites [321]. See sections below for details about use of prescribed fire alone and in combination with other treatments in different plant communities.

Wildfires are more likely to harm northern bobwhite populations than prescribed fires because wildfires are often driven by drought conditions, high winds, and high temperatures, which cause high fire intensity, complete removal of vegetation, and larger burned areas than prescribed fires, while low-intensity prescribed fires often leave patches of unburned habitat including mature shrubs which are critical protective cover for northern bobwhites [316]. Therefore, reducing wildfire hazard is an important management goal for any prescribed fire management program for northern bobwhites [230].

Southeastern Pine Forests

Over a century of fire exclusion and planting for timber have changed forest characteristics and management considerations in southeastern pine forests, and restoration treatments that reduce overstory tree basal area and/or understory woody cover may be necessary prior to implementing a prescribed burning program to create suitable conditions for northern bobwhites [89]. Once the tree canopy is opened and suitable conditions established, prescribed fire is considered “the best management tool” for managing northern bobwhite habitat in southeastern pine forests [215]. In open-canopied pine forests, burning can stimulate the growth of northern bobwhite food plants, and burned areas can provide significantly greater insect biomass than unburned areas. For burning to be effective at maintaining northern bobwhite habitats, however, areas must be 1) burned frequently (see Fire Frequency), 2) burned at low severity (see Fire Severity), and 3) leave a mosaic of unburned areas within the burned area so that nesting and protective cover are available (see Fire Pattern and Size) [14]. In closed-canopied pine forests, fire has little benefit to northern bobwhites because not enough sunlight reaches the forest floor to increase preferred food plants [14,203]. Fire season has important implications for vegetation recovery and exposure of northern bobwhites to direct mortality, and recommended timing varies with management objectives [90,180,187,244,304,321].

Restoration Treatments

Prescribed fire can be difficult to accomplish in southeastern pine forests with a legacy of fire exclusion due to dense fuel accumulations [89,191,229,307]. In longleaf pine forests managed with frequent fire, fallen longleaf pine needles burn quickly, allowing fire to pass under the canopy without killing mature trees. When fire is excluded, pine needles accumulate, and when fire does occur, it can smolder for days, increasing the potential for longleaf pine mortality. In addition, fire-excluded longleaf pine forests can have dense understories of shrubs and small hardwood trees, which are not suitable habitat for northern bobwhites. Under these conditions, wildfires are much more likely to be of high severity and kill canopy trees [89,229,307]. In fire-excluded shortleaf pine communities, dense understories may retain moisture, making prescribed burning less effective at restoring historically open understory conditions suitable for northern bobwhites. Similarly, there is an increased risk of prescribed fire killing mature trees when loblolly pine plantations are densely planted, especially because loblolly pine is relatively less fire-resistant than longleaf pine and shortleaf pine, especially when young [307]. Slash pine occupies a greater range and variety of sites than it did prior to fire exclusion because it establishes in longleaf pine communities in the absence of fire. Prescribed burning in fire-excluded slash pine communities can kill young slash pines that are sensitive to fire, scorch tree crowns, and suppress growth for several years. Prescribed fire can be used to in slash pine communities to either maintain slash pine as the dominant species or restore longleaf pine dominance [180]. Pond pine has highly flammable litter, so even though it grows in moist environments, fires in fire-excluded stands of pond pine can spread rapidly and flames can reach the canopy [89].

In fire-excluded southeastern pine forests and plantations, reducing the overstory and/or woody understory by mechanical thinning, herbicide application, or both may be required to “jump-start” the restoration process before implementing regular prescribed burning treatments to reduce the risk of high-intensity fires that kill canopy trees [89,191,307]. See Glitzenstein et al. (2021) [89] and Noss (2018) [219] for comprehensive information on fire ecology and management of pine forest ecosystems of the Southeastern Coastal Plain. Phillips et al. (2012) provide recommendations for restoring fire-adapted forests in the eastern United States, including southeastern pine, oak-pine, and oak-hickory forests important to northern bobwhites [229] and Stephens et al. (2012) provide information on the effects of fuel reduction treatments in fire-excluded southeastern pine forests to make them more resistant and resilient to fire [278].

Literature reviews recommend creating and maintaining tree canopy cover below 60% [92], 50% [15,280], or 40% [84] in pine and mixed pine-hardwood stands to create suitable habitats for northern bobwhites. Basal area of trees less than about 6 to 14 m2/ha is also recommended [22,65,69,155,160,176,230,251,280]. A review of longleaf pine forest management recommends reducing the basal area below 14 m2/ha, and ideally from 8 to 10 m2/ha, for northern bobwhites [160]. A review about northern bobwhite management in pine forests in the Red Hills concluded that northern bobwhite densities are greatest in areas with low to intermediate basal area, typically <14 m2/ha, and recommends maintaining older pine trees with basal area ranging from 9 to 18 m2/ha to provide habitat for northern bobwhites [69]. Mature tree basal areas of about 12 m2/ha can maximize habitat quality for northern bobwhites and red-cockaded woodpeckers simultaneously, but habitat quality is reduced for northern bobwhites when basal area is greater than about 14 m2/ha [69,196].

Opening the tree canopy prior to conducting prescribed fire allows enough sunlight to reach the forest floor to promote herbaceous and woody food plants in the understory [196,209]. For example, in nine unthinned 6- to 16-year-old longleaf pine stands in Alabama with a fire interval ranging from 2 to 7 years, most of which were in the dormant season, longleaf pine basal area was a significant predictor of the cover of northern bobwhite food plants, herbaceous plants, and woody plants. Specifically, for each 1 m2/ha increase in longleaf basal area, cover of northern bobwhite food plants decreased 1.9%, cover of herbaceous plants decreased 3.5%, and cover of woody plants decreased 2.3% [324]. However, understory woody regeneration is also greatest in areas with low tree basal area, which can result in a dense woody understory that has reduced suitability for northern bobwhites [40]. Therefore, repeated fire or other treatments (e.g., herbicides) is often necessary to maintain suitable northern bobwhite conditions after thinning to a suitable basal area [40,92,142,204,209,213,280]. On the other hand, total elimination of understory hardwood coverts could reduce northern bobwhite protective cover and thereby lower habitat suitability [187,322]. Thinned mid-rotation pine plantations with applications of selective herbicide and prescribed burning to create a pine-grassland structure (i.e., reduced hardwood midstory and more herbs) have higher densities of northern bobwhites compared to untreated control plantations if some hardwood coverts remain (e.g., [143,267,322]). See Miller and Miller (2004) for a review of herbicide use and its influence on biodiversity and wildlife habitat in southern forests with specific examples about northern bobwhites [204].

While hardwood canopy trees such as oaks and hickories provide important mast for northern bobwhites, having too many can degrade pine stands by shading out flammable grasses, dropping fire-resistant leaves, and moderating moisture and temperature at the ground level, thus reducing the efficacy of prescribed fire [196]. Recommendations for how many hardwood canopy trees should remain in pine stands varies. A review of northern bobwhite management in Florida recommends leaving two large (>25 cm DBH) hardwood trees per hectare during thinning operations [213], and the Red Hills Forest Stewardship Guide recommends maintaining one mast-producing hardwood tree for every 2 ha of upland pine habitat for northern bobwhite management [196]. Based on northern bobwhite habitat selection at Fort Bragg Military Installation, Kroeger et al. (2020) recommend a hardwood basal area up to 4 m2/ha in open pine woodlands with a maximum total basal area below 10 m2/ha [155]. Additional recommendations include protecting all hardwood canopy trees in drainages [196].

Increases in saw palmetto cover, height, and density resulting from fire exclusion in pine flatwoods, dry prairies, and some sandhills, results in declining northern bobwhite populations. With increasing saw palmetto dominance, grass cover declines and fires do not spread easily, making it difficult to burn more frequently than approximately every 3 years. Fires also become less intense due to the paucity of fine, flashy fuels, and saw palmetto is not reduced by such low-intensity fires. Thus, saw palmetto remains dominant in the understory at the expense of herbaceous vegetation even if fire is reintroduced after fire exclusion. Managers often use a combination of mechanical pretreatments (e.g., roller chopping, bush hogs, or mechanical removal) and prescribed fire when the goal is to reduce saw palmetto cover and restore a rich herbaceous understory in pine flatwoods or dry prairie [219]. For example, a study in mesic pine flatwoods recommends roller chopping mesic longleaf pine and slash pine flatwoods followed by repeated prescribed fire at ≤2-year intervals based on northern bobwhite occupancy of treated sites and increases in forb richness and density of grasses [20]. However, because there are many negative impacts of roller chopping, (e.g., soil disturbance, increased cover of nonnative plants, substantial mortality of reptiles and other ground-dwelling animals), “burning remains the preferred option” whenever fine fuel and other conditions make it possible [219]. See the review about fire ecology in Florida [219] for more information. See also the FEIS Species Review about saw palmetto.

Because the endangered red-cockaded woodpecker shares habitat requirements with northern bobwhites, northern bobwhite habitat management may be integrated with that of red-cockaded woodpeckers [15,196]. Restoration treatments intended to create open-canopied, herbaceous understory conditions required by red-cockaded woodpeckers can also improve northern bobwhite habitat (e.g., [27,41,80,146,292]). For example, northern bobwhites had higher relative abundance in shortleaf pine-bluestem communities restored for red-cockaded woodpeckers than in untreated control stands [47,292,330]. Similarly, northern bobwhite abundance increased following restoration of a montane longleaf pine woodland in Georgia. The restoration treatments included selective thinning and prescribed fire to reduce tree canopy density of shortleaf pine, loblolly pine, and hardwoods [146]. In eastern Texas loblolly pine-shortleaf pine and longleaf pine stands, northern bobwhite abundance was greater on sites managed for red-cockaded woodpeckers than on control sites. Management practices included hardwood removal from around cavity trees, mechanical removal of midstory and understory vegetation, overstory pine thinning, and prescribed fire, which altered forest structure primarily in the midstory, understory, and herbaceous layers [41]. For more information, see the FEIS Species Review about red-cockaded woodpeckers.

Fire Frequency

In general, frequent fire in southeastern pine forests maintains habitat conditions preferred by northern bobwhites [203]. Many authors recommend maintaining a fire interval between 1 and 5 years and burning in different seasons to provide diverse foods, including fruits and insects, while maintaining small thickets of dense woody plants for protection from predators (e.g., [52,155,196,199,203,208,209,251,283,321]). However, the optimal fire frequency depends on site characteristics [251], and fruits of shrubs are usually reduced the first growing season after fire [139,165,187], so annual burning is not recommended over extensive areas [187]. A review concluded that a 2-year fire interval is “ideal” on mesic sites in temperate climate zones to promote grasses and forbs, otherwise a midstory develops that rapidly reduces northern bobwhite habitat. On sandhill sites and other drier sites, optimal conditions may be created and maintained with an average fire interval of 3 years, coupled with some areas that go unburned for 4 to 5 years to allow for shrub development [321]. In longleaf pine-threeawn communities at Fort Bragg Military Installation, 94% of the fruit was observed 2 years after growing-season (May–June) fire compared with only 6% 1 year after growing-season fire. Fruit production was greater in July following dormant-season (February) fire than in September following growing-season fire. Thus, burning at different intervals and in different seasons and varying firing techniques, while avoiding burning adjacent areas in the same year, may provide adequate fruit production [166].

Darracq et al. (2016) used a comprehensive region-wide database and literature review to examine responses of longleaf pine-associated vertebrates to short (1–3 years), moderate (4–5 years), and long (>5 years) fire intervals. Because longleaf pine specialists—including northern bobwhites, eastern diamondback rattlesnake, Louisiana pine snake, and gopher tortoise—were either primarily associated with sites with moderate fire intervals or used sites across the spectrum of 1- to 5-year intervals, they recommend varying the frequency of fire between 1 and 5 years to benefit the suite of species [52].

Fire Severity

Patchy low-severity fire is most beneficial to northern bobwhites because it removes litter while leaving scattered unburned patches of vegetation. High-severity fires may reduce the quality of northern bobwhite habitat by removing too much protective cover, but in some areas, high-severity fires may reduce woody cover to suitable levels [14,151,196].

Fire Pattern and Size

Northern bobwhite populations require a mosaic of diverse habitats with herbaceous and woody vegetation (see Habitat Composition), so burning to maintain habitat heterogeneity is important for northern bobwhite. In general, fires that leave a mosaic of unburned areas are most beneficial for northern bobwhites by providing foraging sites interspersed with nesting and protective cover [14,15,22,40,77,180,181,186,199]. A single, large, heterogeneous fire or many small fires (<20 ha) may create the desired mosaic on the landscape [15,77] as can pyrodiversity across the landscape [30,264]. A literature review about fire management of northern bobwhite habitat in southeastern pine forests recommends maintaining multiple seral stages all in close proximity, including: 1) open woods annually burned during winter to improve food resources and control parasites; 2) 2- to 3-year-old roughs for nesting and soft mast production; 3) thickets for roosting, loafing, and escape cover, and 4) hard mast-production areas protected from fire [159].

A review of northern bobwhite management in Florida found that northern bobwhites often select edge habitat (see Habitat Composition), and many small burns can create more edge habitat than a single large burn. In addition, northern bobwhites are likely to use entire burns if they are small but avoid the interiors of large, uniform burns until vegetation recovers [213]. Thus, many small burns may benefit northern bobwhites more than a few large burns in the same area (e.g., [323]). However, while the interiors of large, uniform burns are likely to be avoided by northern bobwhites initially, vegetation recovery is rapid and avoidance short-lived [213].

Recommendations for the size of burns in southeastern pine forests for northern bobwhites are varied but typically <50 ha. For example, in pine savanna landscapes in South Carolina, northern bobwhites preferred small burns and burned edges, and burns <50 ha were considered optimal [199]. Similarly, in northern Florida, burned patches between 10 and 40 ha, with interspersed unburned areas, are recommended [291]. In the Red Hills, areas with small burns (about 2 ha) were associated with higher nest production, greater northern bobwhite fall density, and lower risk of mortality than areas with larger burns (about 8 ha) in most years; however, the researchers noted that differences were minor and the additional management costs associated with burning at smaller scales may outweigh the additional population gains. They noted that about four times as many fire breaks are needed in areas with smaller than larger burns. Both sizes of burns used in this study were small (2 and 8 ha) and maintaining suitable protective cover and minimizing ground disturbance during fire break establishment may be just as important as managing for burn size [323].

Patches of woody vegetation left in burned areas are food sources and provide protection from predators [22]. In a review of the benefits of burning in southeastern pine stands for northern bobwhite, Moorman (2002) recommends unburned islands of 0.2 to 0.8 ha be left throughout larger burned areas, leaving nest sites, alternative food sources, and protective cover for wildlife, but noted that low-severity burn patches may provide enough protective cover such that unburned islands may be less important. He also recommended that burning activities be spread across a large area in any given year, leaving newly burned stands adjacent to stands that have not been burned in 1, 2, or 3 years [209]. In areas where protective cover is limiting, measures to promote and protect such cover may be warranted [159]. A review stated that while thickets need to be protected from fire, burning them periodically helps to restrict their growth and maintain a sufficiently open density at ground level for birds to run freely [187]. However, a review about fire effects on northern bobwhites in the Southern Blue Ridge Mountains concluded that protecting patches of dense shrub cover from fire is not typically necessary because low-intensity fire often will not spread under shrub cover and if it does and shrubs are top killed, they readily resprout; in addition, dead stems can provide protective cover prior to resprouting [317].

Fire Season

Historically, fires were most common during the growing season (March–October), but dormant-season fires (September–March)—likely a result of American Indian burning—were also common [70,148,321] (see Fire Regimes). Growing season and dormant season fires can be used for northern bobwhite management in southeastern pine forests with advantages and disadvantages to both [280]. A combination of frequent dormant-season burns and occasional growing-season burns can provide high-quality habitat and food diversity [190,192].

In the southeastern United States, growing-season fire coincides with the timing of reproduction for northern bobwhites (ranging from April to September, with a peak from May to August; see Reproductive Timing: Nesting), making some egg mortality likely in burned areas [15,244] (see Fire-caused Mortality). Burning during the dormant season minimizes direct losses [68], and this is one reason that dormant-season fires have often been recommended in northern bobwhite habitats (e.g., [180,187,213,253,274]). Growing-season fires in spring may be less impactful to northern bobwhite nesting success than growing-season fires in summer because fewer nests are affected prior to peak nesting in summer [46,187] and one study suggests that nest success may be greater in summer [266]. For example, at Tall Timbers Research Station and vicinity, the number of nests peaks in June. Burns in mid-May, when less than 10% of birds were incubating, provided the habitat benefits of growing-season fires (see below) without threatening a high percentage of nests [46]. Females often renest when a nest is destroyed by fire. The probability of renesting, however, declines as the breeding season advances, and nests destroyed by a late summer fire are less likely to be replaced than those destroyed by an earlier growing-season fire (see Nesting and Renesting).

The population level effect of fire-induced nest loss is not well understood, although reviews conclude that the season of fire has minimal population-level effects, in part, because the indirect benefits of habitat improvement may compensate for direct fire-caused mortality [15,148,190]. However, a study on the effects of fire and mechanical treatments on northern bobwhites concluded that large, frequent, growing-season fires may reduce populations of northern bobwhites through direct losses [20]. Nest losses during growing-season fires can be minimized by burning in areas where few nests are found and by conducting small and/or patchy burns [20,46,156,244]. For example, at Tall Timbers, growing-season burns applied to 3-year roughs affect few nests because vegetation is generally too dense for nesting, and growing-season fire in this community improves nesting cover in subsequent years [46]. Special efforts may be required to ensure patchiness, especially during growing-season burns, which tend to be of higher severity than dormant-season burns [244].

Growing-season fires can reduce nesting cover and eliminate suitable nesting or renesting sites until vegetation recovers, which may not occur until late in the nesting season [187,244]. If a fire occurs early in the growing season, vegetation can recover enough to provide nesting cover later in the nesting season, but later growing-season fires might reduce overall nest success if no unburned cover remains [244]. Once vegetation has recovered, recent burns can make good nesting and brood-rearing habitats (see Southeastern Pine Forests). A review of burn timing on breeding birds in southeastern pine forests concluded that the small percentage of nests lost during growing-season burns are offset by overall habitat improvements [46]. The amount of time a site remains unsuitable for nesting depends on the rate of vegetation recovery, but it can take from 4 to 6 months for vegetation to recover after spring fires in southeastern pine forests [187]. One study in Georgia found that 58% of 76 late-summer nests occurred in areas burned the previous March or April [110], and another study in Georgia found that the use of burned sites for nesting increased after mid-June [266] (see Southeastern Pine Forests: Fire Effects on Nesting Habitat).

The timing of burns within the dormant season also has important implications for northern bobwhite protective cover. Early dormant-season fire (e.g., October–February) removes food and protective cover at a time when it grows back slowly, possibly exposing birds to increased predation for long periods, while vegetation recovers rapidly following late dormant-season (e.g., March) fire, so the duration of food loss and exposure to predators is less [80,163,244]. However, if the late dormant-season fire is timed to coincide with raptor migration, for example, in March, when raptor numbers are at their peak, then predation pressure may be greater at this time even if the duration of exposure is less [68,285].

Growing-season and dormant-season fires affect vegetation differently, which can have advantages and disadvantages in northern bobwhite management. In general, repeated, early growing-season burns in southeastern pine forests tend to favor an understory with greater cover of grasses and forbs, whereas dormant-season burns tend to favor sprouting of woody plants [90,180,187,244,304,321]. For more information about how fire season and frequency affect resprouting of woody plants in southeastern pine-grasslands communities, see Robertson and Hmielowski (2014) [247]. Dense hardwood understories are unsuitable habitats for northern bobwhites, but northern bobwhites require patches of protective cover (see Protective Cover for Refuge and Retreat). Where woody plants are too dense to be suitable northern bobwhite habitat, growing-season (mid-April to mid-August) prescribed fires are likely to improve habitat. Where woody cover is sparse, growing-season fires may reduce suitable habitat [192]. A 2022 review about northern bobwhite fire ecology concluded that while growing-season burns can be used to kill understory hardwoods, prescribed fires should be conducted primarily during the late dormant through the early growing season, noting that altering the timing of burns across years and across the landscape is important to maximize the heterogeneity of vegetation [321]. A study about the reproductive ecology of northern bobwhites in Florida recommends both dormant-season (January–mid-April) and growing-season (mid-April–mid-August) prescribed fires be used in northern bobwhite habitat management to create a mosaic of vegetation [192]. A review of fire timing on northern bobwhites at Tall Timbers concluded that “a limited amount of lightning-season (May) fires, compliments more extensive use of winter (February–March) burning for bobwhite habitat management” by reducing understory hardwoods and increasing diversity of plant and insect foods [285].

Oak and Oak-Pine Communities

In a review of fire effects on wildlife in oak-pine savannas in the Central Hardwoods and Appalachians regions, Harper et al. (2016) recommend late dormant-season (March) or early growing-season (April–May) fires at a 2- to 4-year interval to maintain early successional vegetation for northern bobwhites. Because peak northern bobwhite nesting in the region occurs from June to July, they suggested that early growing-season fire would pose relatively little direct effect on northern bobwhite reproduction. They also recommend burning during the late growing-season (September–October) to reduce woody plants, with small (<12 ha) or patchy burns at low intensity, noting that moderate-intensity fire often is necessary to top-kill relatively large woody stems (7–15 cm DBH). They caution against removing too much woody cover at this time because northern bobwhites need woody cover the winter immediately following fire [109]. Thinning—to open the tree canopy and allow light to reach the understory—is recommended prior to implementing a prescribed burning program on previously unmanaged oak savannas [304].

Old Fields

One estimate of optimal habitat for northern bobwhites in mesic Conservation Reserve Program (CRP) grasslands consists of approximately 20% bare ground cover, 40% native warm-season grass cover, 40% forb cover, and moderate (25%–70%) shrub cover [339]. Publications generally recommend burning old fields at ≤5-year intervals to create and maintain optimal habitat for northern bobwhites. In a review about managing early successional habitat for wildlife in the Southeast, Harper (2007) recommends burning frequency be dictated by desired vegetation response, but that annual prescribed fire in old fields in the Southeast generally produces a grass- and forb-dominated plant community, whereas a 2- to 3-year interval generally produces an herbaceous community with scattered shrubs, and a 3- to 4-year interval produces a mixed grass and forb community with a substantial shrub component. Thus, a fire interval of 2- to 4-years that maintains grasses and forbs, allows for soft mast production, and provides shrub cover for winter thermal regulation is likely most beneficial to northern bobwhites in this region [107]. The exact interval depends on the rate of vegetation recovery. A similar recommendation was given for old fields in the Central Hardwoods and Appalachians regions [109]. A study on the effects of fire on old field vegetation in Illinois, recommend burning old fields at intervals of ≤5 years to maintain the most suitable habitat for northern bobwhite, with 4- to 5-year-old fallow fields considered “optimum”. After 5 years, vegetation becomes too dense and habitat quality declines. The researchers recommend burning one third of the area each year in spring so that a diversity of early successional vegetation is available, and nesting cover, which is not available until a few months after burning, is created. They also recommend protecting woody thickets from fire as protective cover to further increase vegetation diversity and edge habitat [298].

A primary objective of improving CRP grasslands for northern bobwhites is to increase native warm-season grasses and associated forbs and reduce nonnative perennial cool-season grasses (e.g., tall fescue, orchardgrass, bromes, timothy, and bluegrasses). Nonnative perennial cool-season grasslands 1) displace desirable native grasses and forbs and other food-producing plants, 2) reduce vegetative diversity by inhibiting seed bank germination, 3) lack sufficient bare ground and therefore limit travel and food accessibility, and 4) have unsuitable habitat structure [95,107,310,318]. Conversion of nonnative perennial cool-season grasslands often involves an integrated approach including prescribed fire, disking, herbicides, and/or seeding of desirable species (e.g., [95,188,189,318]). For example, in tall fescue grasslands in Kentucky, prescribed fire followed by herbicide application in either spring or fall followed by seeding native warm-season grasses is recommended to reduce tall fescue cover, increase native warm-season grass cover, and create warm-season native grasslands that provide good brood-rearing habitat for northern bobwhites [318]. Once converted to warm-season grasslands, integrated methods may again be needed to maintain the desired structure and ratio of forbs to native warm-season grasses and sufficient bare ground [310,339]. For example, in restored warm-season grasslands in Kentucky, dormant-season prescribed fire alone did not maintain suitable habitat because it produced dense stands of native warm-season grasses with little bare ground the first and second summers after fire. Instead, a combination of burning followed by herbicide application was more effective at maintaining suitable habitat [339].

Sericea lespedeza is a nonnative invasive forb that has been commonly used in reclamation. Extensive sericea lespedeza cover can limit the establishment of native herbaceous and woody plants that provide food and protective cover for northern bobwhites throughout the year [18]. Prescribed fire alone generally does not reduce its cover. At Peabody Wildlife Management Area in Kentucky, annual dormant-season (March–April and September–November) prescribed fire stimulated growth and germination of sericea lespedeza and decreased shrub cover for northern bobwhites on reclaimed surface mines planted to native warm-season grasses [17,18]. Other control methods such as integrated methods that include herbicide application may be more effective [18,96]. See Nonnative Invasive Species Management and the FEIS Species Review about sericea lespedeza for more information.

According to a review on managing early successional habitat for wildlife, most fields in the Southeast are burned in the dormant season (January–March) to maintain them in early succession; however, the review recommended restricting burning to later in the dormant season (late March–early April) or late in the growing season (September) for the following reasons:

• Burning early in the dormant season (January–March) can stimulate and increase abundance of nonnative cool-season grasses by clearing the field just before those grasses begin active growth in March, while, burning later in the dormant season (late March–early April) stimulates warm-season grasses and helps reduce abundance of cool-season grasses that have already started growing.
• Burning early in the dormant season reduces protective cover at a time when it may already be limited, while burning in the late dormant season or early growing season (through mid-April) allows wildlife to use the cover in the field throughout winter before spring green-up, while still avoiding direct fire-caused egg losses because they occur before the nesting season.
• Burning in the late growing season (September) reduces woody cover because it top-kills woody stems and reduces resprouting capacity [107].

Another advantage of late-dormant season burning is that it does not coincide with the time when most birds are nesting. In old fields and CRP grasslands in Missouri, a study of nesting chronology suggested that large-scale disturbances (e.g., prescribed fire, mowing, haying, disking, etc.) be avoided in nesting habitat from 1 May when most nests are initiated to 15 September when most breeding activity has ceased. If disturbance must occur during the breeding season, limiting disturbance to one-third or less of nesting habitat and treating the most successionally advanced areas is recommended to reduce the likelihood of encountering nests and young [177].

Tallgrass, Mixedgrass, and Shortgrass Prairies

Northern bobwhites likely benefit from a range of fire intervals in prairie ecosystems that result in variable woody cover and increased structural heterogeneity of vegetation [336,340]. The range of fire intervals best for northern bobwhites depends on burn severity and pattern (patchy versus homogeneous) and the rate of postfire recovery of woody plants in burned areas. Fires should not be more frequent than the time it takes for woody and herbaceous plant structure to recover to conditions suitable for northern bobwhite. In tallgrass prairies, burning at ≥3 to 4 year intervals appears to benefit northern bobwhites more than annual or biennial burning [179,309,340] (see Tallgrass Prairie). Mixedgrass prairie is dominated by woody species that recover quickly after fire (e.g., Havard oak). In contrast, in shortgrass prairies, woody cover is sparser, composed of less fire tolerant species (e.g., lotebush), and therefore likely to recover more slowly [37]. This suggests that relatively longer fire intervals (e.g., >6 or 7 years in plant communities with lotebush) would benefit northern bobwhites more in shortgrass than in mixedgrass communities (see Shortgrass and Mixedgrass Prairie).

In prairies, as in other plant communities, fire occurring during the nesting season may kill eggs and birds (see Fire-caused Mortality); thus, frequent prescribed fires that repeatedly kill eggs and birds may reduce northern bobwhite populations and ground-nesting prairie bird populations in general [239]. Prescribed fire for northern bobwhite management in prairies typically occurs in fall–winter or winter–spring, depending upon objectives. The two burn seasons support different vegetation composition that support different needs in the northern bobwhite life cycle. Prescribed fires in fall–winter promote cool-season grasses and seed-producing forbs while those in winter–spring promote warm-season grasses important for nesting habitat. Summer prescribed fires tend to increase forbs and reduce woody plants [316]. The use of prescribed fires in late summer after the nesting season may minimize direct fire effects on northern bobwhites and most other bird species [239] and also coincides with the timing of most historical lightning-caused fires, although American Indian burning was concentrated in spring and fall [198] (see Fire Regimes). Burning in fall may eliminate protective cover until vegetation growth the following growing season, which may be harmful to northern bobwhites if large areas are burned [44].

Fire or combinations of fire and grazing that promote structural complexity and diversity in prairie ecosystems are likely to improve northern bobwhite habitat, and are likely to maximize bird species diversity, in general [239,321]. In tallgrass and other prairies, conducting many small burns or a single large, patchy burn is likely to increase landscape heterogeneity such that the landscape is more likely to contain all the habitat attributes that northern bobwhites require for their life cycle [91,261]. A review about patch-burn grazing concluded that patch-burn grazing can be used to increase landscape heterogeneity by increasing vegetation structural diversity, increasing plant species diversity, reducing woody cover, and enhancing nutrient cycling [261]. For example, in a landscape with native and restored tallgrass prairies in Missouri, northern bobwhite juveniles that were >35 days old showed stronger selection for sites that were grazed and burned within 2 years compared with sites that were only grazed or only burned [270]. Researchers also recommend integrating patch-burning and livestock grazing as a means of increasing habitat suitability of nonnative buffelgrass pastures for northern bobwhites [91]. For more information on patch-burn grazing, see Tallgrass Prairie.

Texas Rangelands

In the Texas Rolling Plains, Edwards Plateau, and South Texas, habitat management for northern bobwhites typically involves creating or maintaining “islands” of woody cover (e.g., mesquite and lotebush) in grass-forb habitats as protective refugia after a burn [37,118,122,249,262,338] and abundant bunchgrasses and other plants forming suitable nesting clumps (>600–730 nesting clumps/ha) [7,164,226] (see Nest Sites). In general, prescribed fire is considered less important on Texas rangelands than in more mesic regions as low annual rainfall and high grazing pressure often limit the accumulation of sufficient fine fuels to carry fire [122,249]. Fire may be used as the primary method for reducing woody vegetation in some plant communities (e.g., juniper communities) but is more likely to be used in combination with other management tools in other plant communities (e.g., mesquite-grassland communities) [249]. Other management tools include livestock grazing, mechanical methods (grubbing, chaining, disking, etc.), and herbicide application [37,249,262]. General recommendations for managing vegetation cover for northern bobwhites on Texas rangelands include:

• In areas lacking woody cover, create or maintain patches of woody cover (a.k.a., coverts or mottes) comprised of multiple plants of three or more species (e.g., mesquite, lotebush, and hackberry) with a suitable covert at least every 30 m.
• In areas of dense woody cover, create or maintain openings either in strips or patches. Openings should be no farther than about 45 m from woody cover.
• Ensure coverts are comprised of variable sizes and ages of vegetation, including both tall, mature woody vegetation, as well as shorter, young woody vegetation.
• Areas with relatively tall grasses need less woody cover to be suitable than areas lacking them. Woody cover of approximately 15% to 20% (or up to 25%) is suitable on grazed rangelands lacking tall grasses and 5% to 10% woody cover is suitable on ungrazed or lightly grazed rangelands with tall grasses.
• In pastures lacking tall herbaceous cover, the structure of tall, multi-stemmed mesquites and other tall sprouting shrubs may be improved for northern bobwhites by cutting some stems about half-way through and bending them without killing the stem to form a tall, umbrella-like canopy [37,118,122,249,262].
• In dense pastures (e.g., buffelgrass pastures), create patches of bare ground and clumps of bunchgrasses and other vegetation to improve northern bobwhite mobility and nesting habitat [226,262].
• In monocultures, increase plant species diversity. Promote bunchgrasses over sod-forming grasses and include a mixture of low and tall plants, including grasses, forbs, and woody vegetation [262].

A review of quail (including northern bobwhite) habitat management on rangelands stated that the general goal should be the promotion of rangeland heterogeneity and recommends that rangeland management practices be implemented in a manner that 1) preserves uncommon or rare plant community types present on the site, 2) treats smaller portions (e.g., 120 ha) of many pastures rather than larger portions (e.g., 500 ha) of fewer pastures, 3) treats areas of the same pasture with different methods, and 4) treats different areas in different years [58].

Annual prescribed fires are likely too frequent for northern bobwhite habitat management on Texas rangelands, even though woody plants typically sprout and recover quickly after fire. In redberry juniper rangeland in the Texas Rolling Plains, northern bobwhite body condition and total forb density (and prairie broomweed density in particular) was higher in burned areas 4 years after “cool” spring prescribed fires that retained some unburned areas with dense woody plants as loafing coverts than in an 8-year-old burn and an unburned control, suggesting that burning at an interval of less than 8 years might benefit northern bobwhites in these communities. However, during the first postfire year, prairie broomweed densities were lower in burned than unburned areas. Because this species was the single most important food plant for northern bobwhites in the study area, suggested that 1-year-old burns may be less suitable than unburned areas until prairie broomweed increases [173]. Lotebush communities may take up to 7 years after fire before they become useful to northern bobwhites, thus protecting lotebushes during prescribed fires may be warranted [122]. Based on woody vegetation response to fire in honey mesquite-hackberry pastures in the South Texas Rio Grande Plains, a 2-year prescribed fire interval is recommended until the desired structure of woody vegetation is achieved, then maintenance burning on a 3- to 5-year interval [254].

Burns that produce a mosaic pattern of burned and unburned areas provide protective cover beneficial to northern bobwhites [255]. Prescribed fires that have a homogeneous burn pattern that reduce cover of pricklypear, bunchgrasses, and other important protective cover below suitable levels are not recommended because they may reduce reproductive success and adult survival in burned areas until vegetation recovers [35,119]. In general, “cool” fires are likely to create a mosaic of woody and herbaceous vegetation, while “hotter” fires are likely to reduce woody cover below levels that northern bobwhites prefer. On Texas rangelands, prescribed fires in any season are often patchy because of low fuel loads resulting from low annual rainfall and high grazing pressure [42,122]. Generally, fall and early winter prescribed fires promote cool-season grasses and forbs, whereas late winter and spring fires promote warm-season grasses [37,122]. Spring fires may reduce cover of some forbs important to northern bobwhite, such as prairie broomweed [173]. However, adequate moisture after fire can promote abundant forb growth during the second and third years after burning [279].

In the Rio Grande Plain, burning relatively large areas (>100 ha) may be suitable for northern bobwhite habitat management if burns are spotty and discontinuous, leaving unburned areas up to 0.4 ha [170,262]. However, in South Texas, small burned areas (<100 ha) are recommended based on the species’ relatively small home ranges and flight distances [122].

Food Management

Plants

According to a review, whether management intended to increase northern bobwhite plant foods results in an increase in northern bobwhite populations depends on the following conditions:

• Food is limiting northern bobwhite numbers. If food is not limiting, then adding more food will not increase population size.
• No other habitat limitation restricts the population from increasing when food abundance is increased.
• Northern bobwhites can access and use the food created.
• The use of the improved food is sufficient to make a nutritional difference, and northern bobwhites are healthier as a result.
• Improved food benefits the entire population, not just adults.
• Increased food does not lead to other population limitations, such as spread of diseases or increased risk of predation [118].

The review noted that food is generally not limiting for northern bobwhites populations, so increasing plant food abundance generally does not increase population sizes [118]. For this reason, some researchers recommend prioritizing usable space (i.e., suitable protective cover) over food abundance [48]. For example, models suggest northern bobwhite population response following thinning and burning on a 60,000-ha pine-grassland restoration area in Arkansas was less sensitive to changes in food supply relative to changes in usable space, suggesting that ensuring usable space be prioritized over increasing food supply [48].

However, a diverse diet is beneficial to northern bobwhites [150,238] (see Diet), which can be accomplished by providing access to habitats with a range of fire histories and fire timing [23,166]. For example, in northern Florida, sites burned in the growing season (May–June) produced more ragweeds and panicgrasses (that provide desirable food and protective cover) and greater insect prey abundance during brood-rearing months, whereas sites burned during the dormant season (February–March) produced more legumes (that also provide desirable food) and oak sprouts [16]. Burning during different seasons and at different times within the same season provides an array of plant and insect food items and suggests that temporal variation in burning likely benefits northern bobwhites [46,264,291]. In longleaf pine ecosystems, varying fire applications to include growing- and dormant-season fires, incorporating shorter and longer fire intervals, incorporating a variation in firing techniques, and avoiding burning adjacent areas in the same year is recommended to create a diverse diet for wildlife, in general, and to “better emulate historical fires” [166].

Arthropods

A literature review of fire effects on arthropods in the Great Plains concluded that burning to maximize heterogeneity on the landscape—with a mosaic of burned areas and unburned areas (refugia)—would increase arthropod species richness [153]. A literature review on fire effects on insects also suggested that varying the timing and locations of fire and other disturbances could create and maintain diverse habitat niches and therefore insect species diversity [284]. For example, in the Red Hills longleaf pine forest, landscapes with varied fire histories had high species richness and abundance of some insects eaten by northern bobwhite. Bee and butterfly richness, diversity, and abundance increased with the number of unique burn histories within a 250-m radius. Burn histories ranged from 0 to 10 fires between 2007 and 2017. The researchers concluded that a variety of small burns on different burn schedules may increase available resources within the foraging ranges of these pollinator species and that pollinators will benefit from efforts to increase burn heterogeneity and varied burn frequency in southeastern pine forests [302]. In longleaf pine-threeawn stands, using a mixture of growing- and dormant-season fires across the landscape on a 2- to 3-year rotation may promote invertebrate abundance and biomass and provide other benefits to northern bobwhites [320].

Invertebrate abundance is unimportant if juvenile and adult northern bobwhites cannot forage effectively because vegetation and litter are too dense at ground level to allow access to them (see Fire Effects on Food Accessibility). Thus, management practices such as prescribed fire that improve vegetation structure may increase foraging efficiency of northern bobwhites, and therefore increase the accessibility of invertebrates, regardless of abundance [95].

Nonnative Invasive Species Management

Northern bobwhite abundance tends to decline with increasing cover of nonnative grasses [58,118], and areas dominated by nonnative grasses are typically poor habitats for northern bobwhites because their structure and density are generally unsuitable, making movement and foraging difficult and food abundance and diversity less [24,62,71,78,118,158,193,259]. Controlling the spread of nonnative grasses or restoring nonnative grasslands to native grasses and forbs will benefit northern bobwhite. Strategies to prevent invasion or reduce the rate of establishment and spread may involve limiting the amount of disturbance in areas where nonnative grasses are common [118]. Once established, an integrated management approach involving some combination of prescribed fire, herbicide application, physical or mechanical treatment, and/or livestock grazing may help control them [118,158]. Regardless of the approach, nonnative invasive grass management requires repeated treatments for an extended period, replacement of weeds with desirable species, careful land use management, and prevention of new invasions [158,300]. The approach selected depends on a variety of factors including site characteristics and dominant plants. For example, cover of some nonnative grasses such as buffelgrass may increase after fire, so use of prescribed fire alone is typically not recommended. While herbicides may be effective in gaining initial control of a population, they are rarely a complete or long-term solution to weed management [29]. Furthermore, herbicides often reduce the abundance of forbs (important seed-producing plants for northern bobwhites) for at least one growing season after application. Consequently, abundance of plant-eating insects also may be reduced [122]. See the Weed Control Methods Handbook [300] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals. See FEIS Species Reviews for management considerations about individual nonnative invasive species.

Fire Suppression

Eggs, young, and adults are at risk of being sprayed with fire control chemicals, and exposure to some of these chemicals may reduce hatching success, chick weight and liver function (e.g., [28]), and adult survival (e.g., [257]). Mixtures of chemicals may have additive effects [28,207]. The U.S. Forest Service considered northern bobwhites sensitive to fire retardants in their Ecological Risk Assessment of Wildland Fire-fighting Chemicals [207]. For more information, see the following publications: [28,127,207,257,312].