Bobwhite Nests Research Articles

Spatial Analysis of Predator Abundance and Northern Bobwhite Nest Success in Southern Texas

Northern bobwhites (Colinus virginianus) have low nest success across their geographic range, and predation is the primary cause of failure. We evaluated the influence of relative abundance of predators on northern bobwhite nest success. We used data from a long- term radiotelemetry study conducted on 3 sites (800 ha each) in Brooks County, Texas during 2000–2007. We located bobwhite nests (n 1⁄4 456) using radiotelemetry and estimated Mayfield nest success each year. We also estimated relative abundance of nest predators using scent stations (400 3 400 m grid/site) during the nesting season (May–Aug). We developed a gradient map of predator relative abundance and correlated this variable with location-specific bobwhite nest success. Mayfield nest success during the incubation period (23 days) varied between 0.43 and 0.60 during the study. Scent-station visitation rates (% stations visited/night) ranged from 0 to 67%.

Comparing the Accuracy of Egg Candling and Egg Flotation to Estimate the Hatching Date of Northern Bobwhite Clutches

Comparing the Accuracy of Egg Candling and Egg Flotation to Estimate the Hatching Date of Northern Bobwhite Clutches

Influence of Northern Bobwhite Nest Site Selection on Nest Survival in an Agricultural Landscape

Working farms provide excellent potential for conserving northern bobwhite (Colinus virginianus) habitat in agricultural landscapes. Managing for areas of early successional vegetation can increase bobwhite abundance with little reduction in crop production on working farms, but the mechanisms behind the increase is not well known. Our objective was to determine nest site characteristics that may predict nest initiation and survival on agricultural lands to inform future management activities. We radio-collared 241 wild bobwhite on 1 farm with and 2 farms without bobwhite habitat management in southeastern North Carolina. Study sites consisted of a 1,740-ha farm with 9% of property actively managed for early successional cover using areas planted in native vegetation and fallow field borders, a 170-ha farm with 2% of property in early-successional field borders monitored in 2014, and a 395-ha farm with no previous early successional management efforts monitored in 2015. We monitored nests (n = 71) from 15 May to 30 September, 2014 and 2015. We compared vegetation cover between nests and paired reference sites within 250 m of each nest using a generalized linear mixed-effect model. We used measurements of vegetation cover types at nest sites as predictors of nest survival using the Program MARK nest survival model. Bobwhite on the farm with habitat management exhibited higher nest initiation (1 nest/2 marked individuals) than those on unmanaged farms (1 nest/4 marked individuals). On the managed farm, 76% of nests were located in fallow early successional vegetation. Percent forb cover (P = < 0.001) was greater at nest sites on managed (μ = 53.61, SE = 4.32) than unmanaged (μ = 17.01, SE = 2.49) farms. Bobwhite selected nest sites with greater forb cover (β = 1.08, SE = 0.21) than reference sites. Daily nest survival was 0.962 (SE = 0.007) with no covariates that described variation in nest survival rates. Results indicate increasing fallow forb cover on agricultural lands can benefit nest initiation rates by increasing the cover bobwhite select for nesting.

Effect of Meso-Mammal Nest Predator Activity on Northern Bobwhite Nest Success

Perceived changes in predator-prey dynamics along with documented declines of northern bobwhite (Colinus virginianus) have created a renewed interest from biologists and managers about the role meso-mammals play in shaping bobwhite population trajectories. As part of a larger effort to understand this predator-prey relationship, we evaluated meso-mammal activity on sites where bobwhite demographic data was simultaneously being collected via radio- telemetry. During 1999–2006 we conducted 66 meso-mammal activity surveys using scent stations on 16 sites in 3 southeastern states (Florida, Georgia, and Alabama). We calculated an index of meso-mammal activity (PI), for each site, as the average number of station visits per night by raccoons (Procyon lotor), Virginia opossums (Didelphis virginiana), nine-banded armadillos (Dasypus novemcinctus), bobcats (Lynx rufus) and foxes (Vulpes vulpes, Urocyon cinereoargenteus). We collected bobwhite reproductive information on 2,940 nests (x̄ = 45/site, SE = 2.98) from a total of 4,379 radiotagged bobwhites (x̄ = 67/site, SE = 3.81). The average PI for all sites combined was 0.13 (range = 0.03-0.38, SE = 0.01). Nesting success on the sites ranged from 0.29 to 0.72 and averaged 0.52 (SE = 0.01). We used a mixed effects logistic regression model including site as a random effect and observed a negative relationship between the PI and nesting success (β = -1.53 ± 0.72 SE). Our results suggest that meso-mammal activity affects bobwhite nest success, thus, predator management may be warranted at times on some sites to maximize productivity. Future research and modeling efforts should explore the impacts of meso-mammal activity on population growth rates and stability, especially in varying spatial contexts.

Influence of Habitat Type and Prescribed Burning on Feral Swine Depredation of Artificial Quail Nests

Feral swine (Sus scrofa) have increased both spatially and numerically in the Rolling Plains of northwest Texas. Resource managers have little information on the interrelationships between feral swine and native species such as the northern bobwhite (Colinus virginianus). Nest predation by feral swine could adversely affect bobwhite reproduction. Honey mesquite (Prosopis glandulosa) and redberry juniper (Juniperus pinchotii) are the dominant woody plants in northwestern Texas and prescribed burning is used to manage both species. Two experiments were conducted to determine the extent of feral swine depredation on artificial quail nests. In 1992-93, we monitored nest loss in mesquite and juniper habitats for six weeks. Total depredation reached 85 and 98% after three and six weeks respectively, during 1992, compared to 60 and 92% in 1993. Feral swine depredation of artificial bobwhite nests was 33% across years and was evenly distributed between vegetation types. During three-week periods in June and July 1994, depredation was greater (P<0.001) in an unburned (90%) pasture than in unburned areas within a burned (32%) pasture. Decreased predator activity in the burned pasture was probably due to temporary prey displacement and less forage. Feral swine depredation of artificial bobwhite nests was 14% in 1994. Feral swine could potentially have negative impacts for northern bobwhites in mesquite and juniper habitats of northwest Texas.

Habitat Selection of Wild Pigs and Northern Bobwhites in Shrub-Dominated Rangeland

Abstract Sus scrofa L. (Wild Pig) are known to eat the eggs of ground-nesting birds, but it is unknown to what extent they have an impact on populations of Colinus virginianus L. (Northern Bobwhite). We combined data from 2 prior studies conducted on a large ranch in South Texas to assess comparative habit use and selection by Wild Pigs and Bobwhites. Both species were distributed throughout the ranch, but their preferred habitats were very different. Bobwhites favored upland habitats, particularly areas with deep, sandy soils, while Wild Pigs favored low-lying habitats with clay soils. We conclude that depredation of Bobwhite nests by these invasive mammals may be restricted by the thermoregulatory requirement for Wild Pigs to stay near riparian areas. The extent of this effect will depend on the availability and spatial arrangement of water and riparian areas on the landscape.

Nocturnal movements and habitat selection of mesopredators encountering bobwhite nests

ABSTRACTNorthern bobwhites (Colinus virginianus) represent a valuable resource for upland game‐bird hunters and the rural economies they support; however, bobwhite populations are declining across the United States. As ground‐nesting birds, bobwhites are highly susceptible to mammalian predation during the breeding season. We placed global positioning collars on 6 coyotes (Canis latrans), 4 bobcats (Lynx rufus), and 11 raccoons (Procyon lotor) in Texas, USA, during the nesting season of bobwhites (April–August of 2009–2011) to assess their habitat selection and use, as well as determine the relative frequency with which they may encounter bobwhite nests. Overall, nightly encounter rate of predators with known bobwhite nest sites was low. Coyotes encountered nest sites 3 times more frequently than male raccoons and 7 times more frequently than bobcats. Female raccoons did not come within 50 m of any nest locations. The higher encounter rate of coyotes with bobwhite nest sites was associated with the similarity of habitat preference of coyotes and bobwhites for grasslands and grass–shrub habitats and the wide‐ranging nocturnal paths of coyotes. Bobcats and raccoons had shorter nightly paths and mainly used habitats providing a greater degree of cover than is typically suitable for nesting bobwhites. Male raccoons were more mobile than females and made greater use of the grass–shrub habitat, and thus were more likely to encounter quail nests. Despite having lower individual encounter rates with bobwhite nest sites than did coyotes, male raccoons remain important predators of quail nests because they have the behavioral ability to attain greater population densities than those of the more territorial coyotes and bobcats. © 2014 The Wildlife Society.

Fight or flight

Abstract. Patterns of nest defense against predators by ground-nesting bird species in the wild are poorly understood, largely because of a historical inability to directly monitor nests. Most nest-defense studies have observed responses elicited from artificial predators or human observers presented to nesting birds, and few have attempted to present these events in the context of predator—prey relationships found in the wild. We hypothesized that predator threat level (e.g., the threat posed to the clutch or to the clutch and the attending adult), parental characteristics, clutch investment, and future reproductive opportunities would influence avian nest-defense decisions. During 1999–2006, we examined predation events (n = 242) from 790 video-monitored Northern Bobwhite (Colinus virginianus) nests. We evaluated parental, predator, daily, and seasonal correlates that potentially contributed to patterns of nest defense by Northern Bobwhites using a model selection approach. The top model showed that nes...

Predator reduction results in compensatory shifts in losses of avian ground nests

Summary1. Nesting birds can be vulnerable to predation. Wildlife managers sometimes manipulate predator communities to enhance avian productivity and abundance. Managers need to know the predation risk from different predator species responsible for nest failures to maximize success. This issue is especially important when considering reductions in only a part of the predator community in complex ecosystems.2. We conducted a 7‐year crossover experiment at four study sites to examine the effect of mesomammalian predator control on nest success of northern bobwhite Colinus virginianus in the southeastern USA. Nests were monitored using 24‐h near‐infrared video. We hypothesized that nest failures caused by different predator guilds may not be independent and may lead to compensation by other predators as one predator guild was reduced.3. We compared levels of bobwhite nest predation by mesomammals, snakes and other predators in years with and without mesomammal control.4. Control of mesomammal predators reduced the levels of mesomammal nest predation, but predation levels by snakes and other predators increased such that total nest mortality was not reduced. Nest mortality among predator groups was best described as compensatory, and total nest mortality differed among sites.5. Synthesis and applications. Our findings suggest that reductions in predation risk from one predator guild can be compensated by an increased risk from other predators in complex ecosystems. Predator removal within one group may not translate to additive increases in overall nest success, but rather results in shifts in the identity of predators responsible for nest failures. Management efforts focused on manipulating predator communities to enhance avian reproduction are encouraged to examine cause‐specific nest fates to determine the effectiveness of predator reduction programmes.

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

AbstractIntroduced 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.

Nest success of northern bobwhite on managed and unmanaged landscapes in southeast Iowa

AbstractRange‐wide declines in northern bobwhite populations (Colinus virginianus) have been attributed to concomitant loss of breeding habitat. Bobwhite management efforts to restore this habitat resource can be informed by empirical studies of associations between breeding success and multi‐scale habitat attributes. We compared bobwhite nest success in 2 southern Iowa landscapes as a function of microhabitat and landscape composition. Lake Sugema Fish and Wildlife Area (LSWA) was managed to promote bobwhite recruitment, and Harrisburg Township (HT) was an adjacent landscape dominated by private agricultural production. Survival rate modeling based on telemetry data provided evidence for age‐specific daily nest survival rate. Daily survival rates decreased as nest age increased, but the decline was more severe at HT. Nest survival at LSWA (S = 0.495, SE = 0.103) was nearly twice that on HT (S = 0.277, SE = 0.072). We found no evidence that habitat composition or spatial attributes within 210 m of a nest site significantly influenced nest success. Forb canopy at the nest site had a positive influence on nest success at HT but not at LSWA. We suggest nesting habitat with greater forb canopy cover will increase the opportunity for nesting success in landscapes with limited nesting habitat. © 2010 The Wildlife Society.

Does nest-site selection influence bobwhite nesting success in south Florida?

Context. Nest-site selection can influence nesting success, and thus population dynamics, of many species of ground-nesting birds. Despite the economic importance as a game species, populations of northern bobwhites have been declining throughout the southern United States. This paper reports the nesting ecology of northern bobwhites (Colinus virginianus) on Babcock-Webb Wildlife Management Area, Florida, USA, and illustrates the influence of landscape composition and structure on bobwhite nest-site selection and nest fate. Aim. To investigate nest-site selection by bobwhites, to evaluate the influence of landscape composition and structure on nest-site selection, and to identify factors influencing nesting success. Methods. We used distance-based habitat-selection methods and logistic regression to test for nest-site selection and to investigate the influence of landscape characteristics on nesting success. Key results. Bobwhites preferred to establish nests closer to food plots and farther away from water bodies than expected; other habitats were neither preferred nor avoided. Nesting success did not vary across years, differ among habitats or among burn treatments, and none of the habitat and landscape variables we measured significantly influenced the probability that a nest would be successful. Conclusions. Bobwhites preferred to place nests closer to food plots. However, habitat features of nest sites did not influence bobwhite nesting success. These results may indicate that random nest predation by meso-mammalian predators may currently determine fates of bobwhite nests in south Florida, or that population density is low enough that only suitable nesting sites are occupied. Implications. Our results suggest that increasing the density of linear food plots, and maintaining a structurally diverse pine–palmetto and dry prairie habitat that provides adequate nesting cover could contribute to augmenting bobwhite nesting habitat.

Reproduction and Microhabitat Selection in a Sharply Declining Northern Bobwhite Population

Northern Bobwhite (Colinus virginianus) populations have been declining throughout their range, but some of the sharpest declines have been documented in the Mid-Atlantic states. We conducted a 2 year (2006–2007) breeding season (1 May–30 Sep) telemetry study in southern New Jersey to collect baseline data on Northern Bobwhite reproductive rates, and nest and brood microhabitat selection. We located 23 Northern Bobwhite nests, of which 21 were usable for survival analyses. Incubation-period nest survival rate was 0.454 ± 0.010 (95% CI = 0.280–0.727). Mean clutch size was 14.2 ± 0.58 (range 10–19, n = 20) and hatching success was 96.1 ± 2.0% (range 86–100%, n = 10). The estimated probability that an individual that entered the breeding season would initiate incubation of ≥1 nest was 0.687 for females and 0.202 for males. Nest microhabitat selection was positively related to visual obstruction and percentage of litter. Brood microhabitat selection was positively related to visual obstruction, vegetation height, and percentage of forbs but negatively related to percentage of cool season grass and litter. Fecundity metrics for Northern Bobwhites in southern New Jersey appear similar to those reported elsewhere in the species' range. Conservation efforts to increase Northern Bobwhite reproductive success in southern New Jersey should focus on increasing the quantity of available breeding habitat.

Cameras Identify White-tailed Deer Depredating Northern Bobwhite Nests

Odocoileus virginianus (White-tailed Deer) were videotaped depredating two Colinus virginianus (Northern Bobwhite) nests during a nest-predator study in south Georgia in 2002 and 2003. Deer ate eggs from the nests, leading to the failure of one of the two nests.

Raptor Predation of Northern Bobwhite Nests

DEPREDACION DE NIDOS DE COLINUS VIRGINIANUS POR AVES RAPACES Colinus virginianus es una especie que anida en el suelo y tipicamente presenta una tasa de perdida de nidos alta. Hasta hace poco tiempo, la determinacion de las causas de perdida de los nidos se basaba en senales diagnosticas poco confiables registradas en los nidos depredados. Como parte de un estudio exhaustivo sobre la dinamica depredador-presa en C. virginianus (2000–2004), utilizamos monitoreos mediante camaras de video con infrarrojo durante las 24 horas para determinar las causas especificas de la depredacion de nidos. Colocamos camaras de video en 672 nidos de C. virginianus y registramos 249 eventos de depredacion. Las depredaciones fueron hechas por mamiferos (40.2%), serpientes (31.7%), hormigas (11.6%), aves rapaces (1.2%) y por otras causas y por razones desconocidas (15.3%). Durante este estudio registramos tres especies diferentes de aves rapaces depredando nidos de C. virginianus o comiendo sus huevos: un individuo de la especi...

NEST-SITE SELECTION AND NEST SURVIVAL OF NORTHERN BOBWHITE IN SOUTHERN TEXAS

We examined abiotic and biotic variables potentially associated with Northern Bobwhite (Colinus virginianus) nest-site selection and nest success in southern Texas, USA during 2002–2005. These data were used to characterize bobwhite nest-site selection, and to develop and evaluate models of daily nest survival in Program MARK. Nest sites (n = 123) had greater visual obscurity (3.50 vs. 2.60 dm) and vegetation height (64 vs. 47 cm), and less bare ground (11 vs. 25%) compared to random locations (n = 123). The two best models indicated daily nest survival increased with increasing mean maximum temperature and increasing cumulative precipitation. The model-averaged (± SE) estimate for bobwhite daily nest survival was 0.9593 ± 0.0060. These results suggest that bobwhites selected for a specific range of nest-site microhabitat attributes, but that nest predation was largely random. Bobwhite nest survival and productivity in semiarid, subtropical, southern Texas may be largely dependent on weather factors (e.g., temperature and precipitation).

Identifying Predators and Nest Fates of Bobwhites in Southern Texas

Abstract: Predation is the primary cause of nest failure for northern bobwhites (Colinus virginianus). There are few reliable data documenting the species diversity and relative importance of bobwhite nest predators in southern Texas, USA. We used infrared video‐monitoring systems to document nest fates of 127 bobwhite nests over 4 nesting seasons from 2002 to 2005 in southern Texas. A majority of depredation events (83%) were caused by 4 species: coyote (Canis latrans), striped skunk (Mephitis mephitis), southern fire ant (Solenopsis xyloni), and badger (Taxidea taxus). Observed bobwhite nest fates for the study period were 0.50 successful, 0.34 depredated, and 0.16 abandoned or undetermined. A universal approach to mitigating nest predation is not likely to be applicable in regions similar to southern Texas, with high nest‐predator diversity (e.g., fire ants, rodents, and mammalian carnivores). We believe that infrared video surveillance is a valuable tool for documenting baseline information on predator context and nest fate for many avian species, considering the limitations of past methods (e.g., postfate evidence).

EVALUATION OF THE LANDSCAPE SURROUNDING NORTHERN BOBWHITE NEST SITES: A MULTISCALE ANALYSIS

Implementation of the Conservation Reserve Program (CRP) altered the interspersion and abundance of patches of different land-cover types in landscapes of the southeastern United States. Because northern bobwhites (Colinus virginianus) are experiencing significant population declines throughout most of their range, including the Southeast, it is critical to understand the impacts of landscape-scale changes in habitat on their reproductive rates. Our objective was to identify components of landscape structure important in predicting nest site selection by bobwhites at different spatial scales in the Upper Coastal Plain of Georgia. We used a Geographic Information System (GIS) and spatial analysis software to calculate metrics of landscape structure near bobwhite nest sites. Logistic regression was used to model the relationship of nest sites to structure within the surrounding landscape at 4 spatial scales. We found that patch density and open-canopy planted pine were consistently important predictor variables at multiple scales, and other variables were important at various scales. The density of different patch types could be increased by thinning rows of pines in large monotypic stands of closed-canopy planted pine stands. Thinning and creating openings in CRP pine plantations should provide increased nesting opportunities for bobwhites. We interpret the support for other variables in our analysis as an indication that various patch configuration lead to different combinations of landscape structure that provide an acceptable range of habitat conditions for bobwhites.

IDENTIFYING PREDATORS AT NORTHERN BOBWHITE NESTS

Abstract We identified nest predators of northern bobwhites (Colinus virginianus) on private lands in northern Florida and southern Georgia, USA, using continuous infrared micro-video cameras, 1999–2001, and compared these results to predictions based on diagnostic sign at nests. Mammals (59%), snakes (29%), and ants (12%) accounted for known bobwhite nest depredations. Mammalian predators, in order of importance, were the raccoon (Procyon lotor), nine-banded armadillo (Dasypus novemcinctus), Virginia opossum (Didelphis virginiana), bobcat (Lynx rufus), hispid cotton rat (Sigmodon hispidus), and coyote (Canis latrans). Using diagnostic sign, technicians correctly classified 30% of mammalian depredations to species and overestimated nest depredations by snakes. A classification tree model correctly classified 75% of the test sample (n = 33) into “mammal” or “snake” categories, but still overestimated depredations by snakes. We documented a broader predator community upon bobwhite eggs than previously known...

The Evaluation of Nesting Losses and Juvenile Mortality of the Ring-Necked Pheasant

Stoddard (1931, pp. 224-225) concluded after his first 5 years of intensive study of the bob-white quail (Colinus virginianus) in southeastern United States that 60% to 80% of the nesting attempts could normally be expected to fail. Nevertheless, few pairs were completely unsuccessful in bringing off young, as, in the event of loss or abandonment of one or of successive clutches of eggs before hatching, renesting attempts were usually made unless the season was too late or the breeding birds were in poor condition. The heavy nesting losses, therefore, served to delay rather than to prevent the final hatching of a brood by a breeding pair, with a resulting higher percentage of immature birds by fall and a lower total hatch and percentage of young birds reared. No evidence was found that the bob-white made any effort to produce a second brood in the same season if a first was successful. Errington's (1933) data on 69 bob-white nests in Wisconsin, so far as they go, substantiated Stoddard's findings. Like the bob-white, the introduced ring-necked pheasant (Phasianus colchicus torquatus) is capable of repeated renesting attempts during the breeding season if previous efforts to bring off a brood have failed. It, too, appears to be a typically one-brood-per-season bird, though the evidence on this point is not conclusive. We have a record of one pheasant brood hatched about April 30, 1933, and it may be possible that a hen hatching out a brood as early as this may still have time, ability, and inclination to bring off a second brood by mid-summer. Even early young, however, are seldom hatched before the latter part of May in Iowa pheasant range and these are commonly seen in regular company with adults as late as August, when the laying season is essentially