Northern Bobwhite Non-Breeding Habitat Selection in a Longleaf Pine Woodland

Efforts to halt the decline of the northern bobwhite (Colinus virginianus; bobwhite) across its distribution have had limited success. Understanding bobwhite habitat requirements across the annual cycle and at varying scales is essential to aid efforts to conserve bobwhites. We monitored radio-tagged bobwhites from 2016 to 2018 on a 165-km² portion of Fort Bragg Military Installation in the Sandhills physiographic region of North Carolina, USA, to determine factors influencing non-breeding bobwhite habitat selection at multiple scales. We used generalized linear models (GLM) and generalized linear mixed models to assess bobwhite habitat selection at the microsite scale (the immediate vicinity of an animal) and the macrosite scale (across the study area), respectively, by comparing used points to available random points. At the microsite scale, bobwhites strongly selected areas with greater woody understory cover. Also, bobwhite selection increased with greater forb and switchcane (Arundinaria tecta) cover, but this effect plateaued at 65% forb cover and 50% switchcane cover. At the macrosite scale, bobwhites generally selected areas with greater understory cover within a 200-m radius but avoided areas with >55% understory cover; these areas primarily were located in the core areas of drainages with extensive ericaceous vegetation. Bobwhites selected areas with 3–6 m²/ha hardwood basal area in uplands, potentially because of the availability of mast, but avoided uplands when pine (Pinus spp.) or hardwood basal area exceeded 20 m²/ha or 12 m²/ha, respectively, likely because high basal area is associated with increased shading and subsequent loss of understory cover. In addition, bobwhites selected uplands 1 growing season (≥2-month period falling entirely between 1 Apr and 1 Oct) post-fire regardless of burn season. Overall, managers seeking to improve habitat quality for bobwhites in longleaf pine (Pinus palustris) woodlands should employ management practices that maintain available woody understory across the landscape to provide cover during the non-breeding season. © 2020 The Wildlife Society.     

Northern bobwhite response to Conservation Reserve Program habitat and landscape attributes

The northern bobwhite (Colinus virginianus; hereafter bobwhite) has experienced substantial population declines in recent decades in the United States, and especially in Maryland and Delaware. The United States Department of Agriculture's Conservation Reserve Program (CRP) could provide additional habitat for bobwhites, leading to an increase in bobwhite abundance. I investigated if bobwhite abundance was related to the percent cover of CRP land and landscape attributes in local landscapes on Maryland's Eastern Shore and Delaware. Observers conducted bobwhite point transect surveys at 113 locations during the breeding seasons of 2006–2007, and I calculated landscape metrics for 500-m radius landscapes centered on each point transect location. Most CRP land in the study landscapes was planted to herbaceous vegetation. Bobwhite abundance was strongly positively associated with percent cover of CRP land in the landscape but was not strongly related to percent cover of agriculture or forest or to landscape patch density. These results suggest that the CRP has created additional habitat for bobwhites in Maryland and Delaware and that landscapes with greater proportions of herbaceous CRP practices support more bobwhites. © 2012 The Wildlife Society.     

A multispecies approach to manage effects of land cover and weather on upland game birds

Loss and degradation of grasslands in the Great Plains region have resulted in major declines in abundance of grassland bird species. To ensure future viability of grassland bird populations, it is crucial to evaluate specific effects of environmental factors among species to determine drivers of population decline and develop effective conservation strategies. We used threshold models to quantify the effects of land cover and weather changes in "lesser prairie‐chicken" and "greater prairie‐chicken" (Tympanuchus pallidicinctus and T. cupido, respectively), northern bobwhites (Colinus virginianus), and ring‐necked pheasants (Phasianus colchicus). We demonstrated a novel approach for estimating landscape conditions needed to optimize abundance across multiple species at a variety of spatial scales. Abundance of all four species was highest following wet summers and dry winters. Prairie chicken and ring‐necked pheasant abundance was highest following cool winters, while northern bobwhite abundance was highest following warm winters. Greater prairie chicken and northern bobwhite abundance was also highest following cooler summers. Optimal abundance of each species occurred in landscapes that represented a grassland and cropland mosaic, though prairie chicken abundance was optimized in landscapes with more grassland and less edge habitat than northern bobwhites and ring‐necked pheasants. Because these effects differed among species, managing for an optimal landscape for multiple species may not be the optimal scenario for any one species.     

A maximum entropy and GIS approach to predict potential habitat for northern bobwhites in the Black Belt prairie physiographic region of Alabama

Northern bobwhite (Colinus virginianus) populations have sustained precipitous declines throughout their range. The North American Breeding Bird Survey for Alabama indicates a rate of decline of over 6% per year since 1966. Declining bobwhite populations have been associated with large-scale habitat loss and a reduction in habitat quality due to advances in ecological succession, intensive monoculture agriculture, and intensive timber management practices. Once a very diverse region, modern land-use practices throughout the Black Belt Prairie physiographic region have created a simplified landscape that have left few places where bobwhites can live and thrive. Despite extensive research on bobwhites, there is insufficient knowledge on the spatial distribution of bobwhite habitat on a regional scale, including the Black Belt Prairie physiographic region. Knowing the spatial distribution of suitable bobwhite habitat will allow conservation planners to prioritize efforts and direct limited resources to achieve conservation goals for the region. The goals of this study were to 1) evaluate the maximum entropy modeling approach for predicting northern bobwhite habitat in the Black Belt Prairie physiographic region, and 2) develop a northern bobwhite habitat suitability map for the Black Belt Prairie physiographic region. The results showed that deciduous 1.8 km (1.8 km is the dispersal distance of bobwhites) neighborhood was the most important habitat variable, followed by water 1.8 km neighborhood. Developed 1.8 km neighborhood was the most important anthropogenic variable, ranking third in overall importance. The resultant model denotes potential habitat in the region and forms the basis for using the maximum entropy and geographic information system approach to predict suitable habitat and prioritize areas for conservation.     

Sika deer distribution and habitat selection: the influence of the availability and distribution of food, cover, and threats

Large populations of sika deer occur in lowland heath, woodland, and grassland mosaics in southern England. Previous studies have focused on understanding single factors potentially affecting distribution and habitat selection of sika deer rather than considering simultaneously effects of landscape configuration and human disturbance on their distribution and habitat selection. This study measured effects of habitat availability, landscape structure, and human disturbance on where sika deer placed their home ranges and habitat selection within those ranges. Two main hypotheses were tested: (1) habitat selection differs according to landscape structure and habitat availability at both landscape and home range scales and (2) distribution of sources of human disturbance within the home range of deer affects their distribution. Results from radiotracking 31 females provided support for the first hypothesis and partial support for the second. Habitat selection at the landscape and home range scales differed between landscapes with different habitat structure and availability and was driven by distribution and availability of food and cover and a perceived risk linked to disturbance. Furthermore, deer selected open areas close to cover and this selection was stronger with presence of human disturbance, although results differed between study areas with different habitat distribution and level of disturbance. The study highlights the importance for managing deer of a balance between grazing and cover resources and the distribution of human disturbance.     

Northern bobwhite breeding season habitat selection in fire-maintained pine woodland

Despite the acknowledged importance of prescribed fire in creating northern bobwhite (Colinus virginianus) breeding cover, little research has investigated bobwhite breeding season habitat selection relative to time since fire. In 2016 and 2017, we monitored radio-tagged bobwhite on a 17,000-ha portion of a military installation managed with frequent (every ~3 years) prescribed fires, applied during the growing and dormant seasons. We monitored bobwhite to determine which vegetation characteristics associated with prescribed burning were important to bobwhite breeding season habitat selection at the microsite (i.e., telemetry location compared to nearby random location) and the macrosite scale (i.e., the burn-unit containing the location compared to study area availability). During 2 breeding seasons, we collected 2,315 bobwhite locations and compared percent cover of vegetation, days since burn, basal area, and distance to key landscape features (e.g., stream, wildlife opening) at a subset of microsite locations (301 locations during 2016 and 890 locations during 2017) to paired random locations. At the microsite scale, bobwhite selected lower basal area of hardwoods, greater woody understory cover, greater other (not wiregrass [Aristida stricta]) grass cover, and greater forb cover than at random points. At the macrosite scale, bobwhite selected units with <4.6 m²/ha basal area (combined hardwoods and pines) in 2016 and units with <9.2 m²/ha basal area in 2017. At the macrosite scale, bobwhite selected for areas burned in the dormant season of the same year, avoided areas burned in the growing season of the same year, and used other times since last burn categories proportionate to their availability. The selection for a low basal area at both scales indicates prescribed fire effects would be limited by shading from dense overstory, and the shrubs, grasses, and forbs that provide essential cover for bobwhite during the breeding season will not develop. In lower productivity soil regions similar to our study area, we advise that thinning operations set target basal areas below 10 m²/ha to create and maintain breeding season habitat for northern bobwhite. © 2019 The Wildlife Society     

Life on the edge: Northern bobwhite ecology at the northern periphery of their range

Over the past 40 years, Northern bobwhite (Colinus virginianus) populations have declined range-wide. The Mid-Atlantic once held the highest densities in the country and now shows some of the worst declines. Although population parameters have been quantified throughout most of the bobwhite range, Mid-Atlantic populations have been largely unstudied. To better quantify the dynamics of this declining system, we sought to not only gather annual data on home range, movement, and habitat selection, but also examine how some of these metrics might impact survival. We captured and radio-tracked 154 bobwhites between May 2006 and April 2008 on a 125 km² area of Cumberland County, New Jersey, USA. Seasonal daily movement ranged from 146 m to 158 m but several extreme movements were notable. Across seasons, grassland habitat was used in greater proportion to its availability, shrub-scrub and agriculture habitats were used equally with their availability and forests and other habitats were used less than their availability. Differences in second-order selection occurred between seasons with lower use of shrub-scrub and forest habitats and higher use of other habitat in breeding seasons. Pooled breeding season survival was 0.343, nonbreeding season survival was 0.183, and annual survival was 0.063. Although mortality was dominated by avian predators, house cat mortalities were noteworthy. Cox proportional hazard analysis revealed that risk of breeding season mortality risk was increased by longer daily movement, lower grassland use, and higher forest and other use. During the nonbreeding season, risk of mortality increased with shorter daily movement and proximity to occupied buildings and barns. This information could inform management decisions in the greater Mid-Atlantic as well as other areas of their range where they exist at very low abundances. © 2010 The Wildlife Society.     

A Hierarchical Analysis of Habitat Selection by Raccoons in Northern Indiana

Abstract: Although numerous studies have examined habitat use by raccoons (Procyon lotor), information regarding seasonal habitat selection related to resource availability in agricultural landscapes is lacking for this species. Additionally, few studies using radiotelemetry have investigated habitat selection at multiple spatial scales or core-use areas by raccoons. We examined seasonal habitat selection of 55 (31 M, 24 F) adult raccoons at 3 hierarchical orders defined by the movement behavior of this species (second-order home range, second-order core-use area, and third-order home range) in northern Indiana, USA, from May 2003 to June 2005. Using compositional analysis, we assessed whether habitat selection differed from random and ranked habitat types in order of selection during the crop growing period (season 1) and corn maturation period (season 2), which represented substantial shifts in resource availability to raccoons. Habitat rankings differed across hierarchical orders, between seasons within hierarchical orders, and between sexes within seasons; however, seasonal and intersexual patterns of habitat selection were not consistent across hierarchical orders of spatial scale. When nonrandom utilization was detected, both sexes consistently selected forest cover over other available habitats. Seasonal differences in habitat selection were most evident at the core-area scale, where raccoon selection of agricultural lands was highest during the maturation season when corn was available as a direct food source. Habitat use did not differ from availability for either sex in either season at the third-order scale. The selection of forest cover across both seasons and all spatial orders suggested that raccoon distribution and abundance in fragmented landscapes is likely dependent on the availability and distribution of forest cover, or habitats associated with forest (i.e., water), within the landscape. The lack of consistency in habitat selection across hierarchical scales further exemplifies the need to examine multiple biological scales in habitat-selection studies.     

Landscape Connectivity Influences Survival and Resource Use following Long-Distance Translocation of Northern Bobwhite

Translocation is an important component of northern bobwhite (Colinus virginianus) recovery efforts, given the scale of their decline and inability to rapidly recolonize recently restored habitat. Repopulating sites in northern latitudes that are distant from reliable source populations may require long-distance trap and transport from southern locales, potentially compounding existing obstacles for this renascent population recovery technique. The landscape connectivity hypothesis predicts that site fidelity and survival would be lower if release properties are small and fragmented and home range sizes would be smaller and dispersal distances would be lower if habitat quality at the release site is perceived to be high and the surrounding matrix is of low permeability. We evaluated this hypothesis to determine if northern bobwhite survival, site fidelity, and resource selection following translocation differed between 2 contrasting landscapes in the Mid-Atlantic region of the United States. We translocated 508 radio-collared northern bobwhites from northern Florida and southern Georgia, to small, fragmented properties on the eastern shore of Maryland and large, contiguous properties in southern New Jersey, USA. We monitored northern bobwhites via radio-telemetry from approximately 1 April through 30 September, 2015–2018, 2–7 times a week. Breeding season (182 days after release) survival varied among sites, and was generally higher at the 2 New Jersey release sites than at the 2 Maryland sites, yet an acclimation period is ostensibly required to obtain reasonable breeding survival estimates to elicit population growth. Site fidelity, maximum dispersal distances, and home range sizes were lower at the smaller, fragmented Maryland properties than the larger New Jersey properties. These results support the landscape connectivity hypothesis such that reduced connectivity in our study decreased site fidelity and survival. Temporal variation in survival was potentially an artifact of translocation stress or maladaptive behavior during initial acclimation to the release sites, indicating that higher stocking rates may be needed to provide adequate founder abundance for translocation success. Northern bobwhites used early-successional cover at all sites, though selection varied based on scale of analysis and landscape context. These vital rate estimates and resource use patterns should be used to guide future translocations within the Mid-Atlantic, provide perspective for this population restoration technique range wide, and stimulate further investigation into limiting factors. © 2020 The Wildlife Society.     

Habitat Availability Is a More Plausible Explanation than Insecticide Acute Toxicity for U.S. Grassland Bird Species Declines

Grassland bird species have experienced substantial declines in North America. These declines have been largely attributed to habitat loss and degradation, especially from agricultural practices and intensification (the habitat-availability hypothesis). A recent analysis of North American Breeding Bird Survey (BBS) “grassland breeding” bird trends reported the surprising conclusion that insecticide acute toxicity was a better correlate of grassland bird declines in North America from 1980–2003 (the insecticide-acute-toxicity hypothesis) than was habitat loss through agricultural intensification. In this paper we reached the opposite conclusion. We used an alternative statistical approach with additional habitat covariates to analyze the same grassland bird trends over the same time frame. Grassland bird trends were positively associated with increases in area of Conservation Reserve Program (CRP) lands and cropland used as pasture, whereas the effect of insecticide acute toxicity on bird trends was uncertain. Our models suggested that acute insecticide risk potentially has a detrimental effect on grassland bird trends, but models representing the habitat-availability hypothesis were 1.3–21.0 times better supported than models representing the insecticide-acute-toxicity hypothesis. Based on point estimates of effect sizes, CRP area and agricultural intensification had approximately 3.6 and 1.6 times more effect on grassland bird trends than lethal insecticide risk, respectively. Our findings suggest that preserving remaining grasslands is crucial to conserving grassland bird populations. The amount of grassland that has been lost in North America since 1980 is well documented, continuing, and staggering whereas insecticide use greatly declined prior to the 1990s. Grassland birds will likely benefit from the de-intensification of agricultural practices and the interspersion of pastures, Conservation Reserve Program lands, rangelands and other grassland habitats into existing agricultural landscapes.     

Vegetation Structural Attributes Providing Thermal Refugia for Northern Bobwhites

The northern bobwhite (Colinus virginianus; bobwhite) exists at the edge of its thermal tolerance in southern Texas, USA, a region characterized by extreme heat and periodic drought. Extreme heat and drought events are predicted to increase in frequency and intensity in semi-arid regions, leading biologists to emphasize management of thermal cover. The degree to which temperatures within patches of woody vegetation vary and the specific vegetation structural characteristics that create cooler microclimates within these patches are unknown. We evaluated temperature variation between selected and available sites, vegetation characteristics facilitating cooler microsites, and whether these characteristics in addition to temperature were important predictors of microsite selection within woody patches. We radio-tracked 83 bobwhites 2–3 times/week during April–August 2017–2018. We recorded operative and ground surface temperatures and measured woody and herbaceous vegetation height, canopy density, and overlapping woody and herbaceous cover at used and paired random locations. Within the same woody patch, 80% of used locations contained operative temperatures lower than or equal to random locations. There was a weak relationship between the vegetation variables we measured and temperature at paired locations, indicating that none of the vegetation variables alone can effectively reduce temperatures. Temperatures within woody patches are likely strongly tied to diurnal variation in solar angle and ability to create shade. Cooler temperatures, dense canopies, and overlapping woody vegetation had the greatest effects on relative probability of microsite use during the middle of the day, whereas warmer temperatures and taller woody vegetation had the greatest relative effects during the morning and evening. Our results suggest that temperature was influential across diurnal periods but foraging and predation avoidance may have also been important. Maintenance and preservation of dense woody vegetation and diverse shrub understories must be prioritized in habitat management for bobwhites in semi-arid regions. © 2021 The Wildlife Society.     

Aspects of northern bobwhite ecology on south Florida US pastureland

During 2004 and 2005, we monitored breeding season survival, home range, habitat use, density, and reproduction of northern bobwhite (Colinus virginianus) in the peninsular region of Florida, USA. We radio-tagged 81 birds across a 20-km² cattle ranch consisting predominately of rotationally grazed pastureland. Birds were radio-tracked three to five times per week until mortality or the transition to nonbreeding season. We found no difference in home range size among the sexes, ages, or their interaction. Mean home range size pooled for years, sexes, and age class was 56.28 ha (±7.87 SE). Home ranges of bobwhites were not distributed among habitats randomly (second order: Λ?=?0.10; 7, 35 df; P?=?0.002). In addition, bobwhites did not use the habitats within their home range at random (third order: Λ?=?0.14, 5, 35 df; P?=?0.02). Estimated seasonal survival was 0.28 (±0.12 SE) and was best explained by the time-dependent model. Reproductive metrics indicated adequate reproduction and values consistent with the bobwhite literature. Bobwhite density (birds per hectare) in 2004 was 0.52 (±0.54 95 % confidence interval [CI]) and 0.75 (±0.51 95 % CI) for 2005. These results suggest that pastureland landscapes managed with rotational grazing can support bobwhite populations, albeit at low densities. More conservation attention should be directed towards improving these systems for bobwhite restoration.     

Strategic Grassland Bird Conservation throughout the Annual Cycle: Linking Policy Alternatives,Landowner Decisions,and Biological Population Outcomes

Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds.     

Effects of Understory Vegetation Management on Brood Habitat for Northern Bobwhites

Abstract: Northern bobwhite (Colinus virginianus) populations have experienced severe declines for several decades, and declines have been particularly precipitous in the southern United States. These declines are partially attributable to large-scale conversions of potential habitat to short-rotation pine (Pinus spp.) forests managed for wood fiber production and fire exclusion in pine-dominated landscapes. We used standard arthropod sampling techniques, human-imprinted bobwhite chicks, and vegetation response to evaluate effects of different understory vegetation management practices on brood habitat quality within a commercially managed pine forest in Louisiana, USA, during 2002–2005. Specifically, we evaluated effects of mowing, prescribed fire during the growing season, prescribed fire in combination with imazapyr application, and no vegetation management on arthropod abundance and diversity, vegetation response, and the probability of bobwhite chicks successfully capturing an arthropod. Bobwhite chicks were more successful at capturing arthropods, and arthropod abundance and diversity were greatest, in plant communities managed using prescribed fire and imazapyr. Forest stands managed using a combination of fire and imazapyr were managed primarily to benefit the federally endangered red-cockaded woodpecker (Picoides borealis; RCW). Our findings suggest that management directed toward improving forest condition for RCWs improves habitat quality for brooding bobwhites. However, bobwhite chicks in our study area were less successful at capturing arthropods than were chicks in other studies in the southeastern United States. Brood-rearing habitat in pine forests similar to those we studied may be of generally poor quality, and could be related to precipitous declines of bobwhites in the West Gulf Coastal Plain. Managers should recognize that creating high-quality brood habitat in forests similar to those we studied will require more intensive management of understory vegetation than we studied.     

Habitat Value of Intensively Established Pine Plantations for Northern Bobwhite

ABSTRACT Declines in northern bobwhite (Colinus virginianus; bobwhite) populations in the southeastern United States may be partially attributable to loss of early successional plant cover associated with greater use of herbicides in forest management. We tested effects of 5 levels of operational plantation establishment intensity on vegetation communities and structure important for bobwhite in 1–5-year-old loblolly pine (Pinus taeda) plantations (n = 4) in the Outer Coastal Plain Mixed Forest of Mississippi. We compared results with values reported in the literature to calculate usable space for winter food, loafing, nesting, and brood-rearing at 2 levels of spatial resolution. Treatments (k = 5) reflected a range of management intensities and were combinations of mechanical site preparation, chemical site preparation (CSP), and herbaceous weed control (HWC). Coverage of winter food plants in the least intensive treatment was more than double that in the most intensive; however, differences in usable space of winter food cover were negligible due to improved accessibility in more intensive treatments. Although CSP reduced coverage of nonpine woody plants across all years, loafing cover reached adequate levels by year 3 in all treatments. Usable nesting cover was <4% across all years and treatments and was nearly eliminated by the reduction in herbaceous cover and visual screening cover following broadcast HWC. Optimal brood-rearing habitat was virtually absent in all treatments and years due to the lack of conjoint occurrence of bare ground and forb canopy. Although bobwhite habitat may have been promoted by formerly widespread plantation establishment methods that involved wide-scale soil disturbance, those established using newer methods with less soil disturbance are likely inadequate for most bobwhite habitat requirements. Efforts to provide bobwhite habitat in plantation-dominated landscapes may have to rely on management of thinned mid-rotation stands and permanent landscape features such as rights-of-way. The value of young plantations for bobwhite may be increased by reducing management intensity or increasing spacing between planting rows, thus increasing time before crown closure and providing opportunity for understory manipulations.     

Effects of fire management on northern bobwhite brood ecology

Northern Bobwhite Colinus virginianus chicks require ample invertebrates for growth and feather development. Early successional or resprouting vegetation provides invertebrates for chicks but may not provide other resources such as roosting and loafing cover that is typically provided by later successional stages. Thus, management for bobwhites provides multiple seral stages in close proximity but the effects of landscape interspersion have not been tested for bobwhite broods. During a 2-year study, we explored the effects of landscape complementation and food availability on growth and survival of bobwhite chicks. We found growth of chicks to be negatively related to home range size which was negatively correlated to the amount of area burned. We also found survival of chicks to be positively related to the amount of burned area (i.e., foraging area) within brood home ranges. To maximize the growth and survival of bobwhite chicks, it would be necessary to increase access to foraging areas while decreasing the size of brood home ranges. Access to foraging areas can be created through frequent prescribed fire at small spatial scales.     

Patterns of space and habitat use by northern bobwhites in South Florida,USA

The manner by which animals use space and select resources can have important management consequences. We studied patterns of habitat selection by northern bobwhites (Colinus virginianus) on Babcock-Webb Wildlife Management Area, Charlotte County, Florida and evaluated factors influencing the sizes of their home ranges. A total of 1,245 radio-tagged bobwhites were monitored for 19,467 radio days during 2002–2007. The mean ( ± 1 SE) annual home range size, estimated using the Kernel density method, was 88.43 ( ± 6.16) ha and did not differ between genders. Winter home ranges of bobwhites (69.27 ± 4.92 ha) were generally larger than summer home ranges (53.90 ± 4.93 ha). Annual and winter home ranges were smaller for bobwhites whose ranges contained food plots compared to those that did not; however, the presence of food plots did not influence summer home ranges. We used distance-based methods to investigate habitat selection by bobwhites at two scales: selection of home ranges within the study site (second-order selection) and selection of habitats within home ranges (third-order selection). Across both scales, bobwhites generally preferred food plots and dry prairie habitat and avoided wet prairies and roads. This pattern was generally consistent between genders and across years. Our data indicate that management practices aimed at increasing and maintaining a matrix of food plots and dry prairie habitat would provide the most favorable environment for bobwhites.     

An improved multi-scale approach to modeling habitat occupancy of northern bobwhite

Predicting species presence requires knowledge of detection of individuals, scale of model variables, model selection uncertainty, and spatial autocorrelation. Our objective was to incorporate recent modeling advances to predict potential habitat occupancy of northern bobwhite (Colinus virginianus). From 15 May–15 August 2008 and 2009, we conducted repeat-visit surveys at 360 sites within Delaware to sample presence of bobwhite. We randomly selected half the data to model scale-dependent relationships of bobwhite presence with metrics of landscape- and site-scale habitat composition and configuration. The final averaged habitat-occupancy model fit the remainder testing dataset with an area under the receiver operating characteristic curve value of 0.62. At the site scale, bobwhite presence was negatively related to interspersion and juxtaposition of early successional habitat (ESH; grassland and shrubland), ESH to forest edge density, and agriculture to forest edge density, though relative effect sizes were weak to moderate after accounting for model selection uncertainty. At the landscape scale, bobwhite presence was negatively related to patch cohesion of human development within 2.5 km and positively related to patch cohesion of ESH within 2.0 km, with both variables exerting strong effects. Bobwhite presence was also weakly and positively related to percentage of shrubland habitat within 1.0 km of the sampling point. We applied our habitat occupancy model to map the predicted presence of breeding bobwhite within the Delmarva Peninsula, USA. The modeling results and distribution map will provide guidance to State and Federal private land management programs in the Mid-Atlantic to identify where habitat management efforts will be most effective. Our methodology can also serve as a basis for future habitat modeling of bobwhite and other grassland–shrubland species across their range. © 2011 The Wildlife Society.     

Northern Bobwhites and Postfire Succession

ABSTRACT Our study evaluated the effects of prescribed fire on northern bobwhites (Colinus virginianus) occupying native rangelands in Rolling Plains of Texas, USA, during 2002 and 2003. Prescribed fires were conducted during February of 1996, 1998, and 2000; pastures with no recent treatment history served as controls. We quantified bobwhite densities from line transects using distance sampling. We used a repeated-measures analysis of variance to test for treatment-year differences in bobwhite densities. We measured postfire herbaceous and woody vegetation attributes and evaluated vegetation relationships to bobwhite density using simple linear regression. We found significant between-year differences in fall bobwhite densities (F = 13.05, df = 3, P = 0.036) but no differences among treatments or controls. Fall bobwhite densities were inversely related to visual obstruction (r² = 0.179, df = 15, P = 0.058) and positively associated with increasing heterogeneity of grass cover (r² = 0.416, df = 15, P = 0.004). Our results suggest prescribed fire at large spatial scales may be a neutral practice for managing bobwhite habitat on semiarid rangelands.     

Impacts of introduced grasses on breeding season habitat use by northern bobwhite in the South Texas plains

Introduced grasses may affect diversity of native fauna and flora adversely, and disrupt ecosystem processes. Many rangelands in South Texas have been seeded to or have been colonized by buffelgrass (Pennisetum ciliare) and Lehmann lovegrass (Eragrostis lehmanniana), perennial bunchgrasses native to Africa. The objective of this research was to quantify impacts that these 2 species of introduced grasses may have on northern bobwhite (Colinus virginianus) habitat use on South Texas rangelands during the breeding period (Apr–Aug). We evaluated the effects of buffelgrass and Lehmann lovegrass on northern bobwhite nest habitat (n = 35 nests) and general habitat use sites (n = 86 radiomarked quail) with logistic regression and habitat selection functions based on simple saddlepoint approximations. Buffelgrass was used as a nesting substrate at 11% of nests; however, vegetation height and visual obstruction between 1 cm and 30 cm were the best predictors of nest site use. Areas of introduced grass coverage ≥15–20% were avoided by northern bobwhites at general habitat use organism-centered points, but not at nest site use points. Introduced grass coverage and forb coverage were the best predictors of general habitat use, and bobwhites avoided areas with ≥18% introduced grass cover. These results suggest that avoidance of areas with extensive introduced grass cover may indicate a reduction in usable habitat space for northern bobwhite in the western South Texas plains. Maintaining native grass stands while implementing localized control of introduced grasses could be used as a strategy to promote habitat for northern bobwhites. © 2011 The Wildlife Society.