Colinus Virginianus Research Articles

Efficacy of a Preemergence Herbicide Following Postemergence Control to Reduce Sericea Lespedeza in Old Fields Managed for Northern Bobwhite

Sericea lespedeza (Lespedeza cuneata; hereafter, sericea) is a nonnative forb that commonly invades sites managed for northern bobwhite (Colinus virginianus; hereafter, bobwhite). Sericea can reduce habitat quality for bobwhite as it outcompetes native plants that provide forage and cover. Bobwhite eat sericea seed, but seed are relatively indigestible and may limit nutrition intake and reduce the fecundity rate. Postemergence herbicides, including glyphosate, triclopyr, and fluroxypyr+triclopyr, control standing sericea, but do not provide preemergence control, which would increase long-term control because sericea annually produces large amounts of hard seed with high dormancy rates. Imazapic is labeled to provide preemergence control, but no study has evaluated preemergence applications of imazapic following postemergence herbicides to control sericea and promote native plants important for bobwhite. Additionally, data evaluating various rates of imazapic to control sericea are lacking. We currently are evaluating the efficacy of glyphosate and fluroxypyr+triclopyr, applied alone post-emergence and in conjunction with 3 preemergence rates of imazapic, to reduce coverage of sericea at 4 sites in Tennessee and Alabama, USA. We split each site into 8 treatment units and control and assigned the following treatments: glyphosate, fluroxypyr+triclopyr, glyphosate with 48, 96, and 144 ml/ha (4, 8, and 12 oz/acre) imazapic, and fluroxypyr+triclopyr with 48, 96, and 144 ml/ha imazapic. We applied 767 ml/ha (2 qt/acre) glyphosate and 192 ml/ha (16 oz/acre) fluroxypyr+triclopyr in August 2018 to control established sericea. We measured coverage of native forbs, native grasses, and sericea during the 2019 and 2020 growing seasons to determine the efficacy of treatments on sericea and the native plant community. Both glyphosate and fluroxypyr+triclopyr reduced sericea coverage 1 and 2 growing seasons following treatment, but we documented no difference in reduction of sericea coverage between postemergence treatments. We will apply imazapic in March 2021 at 3 different rates to determine whether a preemergence application improves sericea control. Our results on the effectiveness of a preemergence application after postemergence applications should provide valuable information to managers trying to control sericea on lands managed for bobwhite.

Results from Kentucky’s 10-year Bobwhite Recovery Plan

The northern bobwhite (Colinus virginianus; hereafter, bobwhite) has experienced a precipitous population decline through almost all its historical range over the last 6 decades. We initiated a 10-year restoration plan in Kentucky, USA in 2008 and reported on it through 3 published “Road to Recovery” reports along with 30 peer-reviewed articles and abstracts, 2 technical documents, 7 theses or dissertations, and 11 popular literature pieces. Seven Quail Focus Areas were selected across the state based on site personnel, geographic position (east to west), and land ownership (e.g., private, public, state, federal) for monitoring and habitat management. The focus areas averaged 11,895 acres and area managed for quail on an annual basis ranged from 9% to 42%. Management took the form of herbicide applications, disking, fire, planting, grazing, control of woody vegetation, and mowing. Hierarchical distance sampling models using time-of-removal information to inform detection processes were used to assess bobwhite density on each focus area. Models were based on spring breeding bird point counts in which a suite of grassland songbirds were recorded and fall covey counts in which only bobwhite were recorded. Roadside surveys (direct observation) and hunter harvest information were also used for statewide comparisons of focus areas and statewide trends. Across all years and focus areas a 40% increase in the quail population was observed in 20 years (38%) of the possible 53 years of survey data. Stable to increasing trends were also observed in focal area populations of dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), eastern kingbird (Tyrannus tyrannus), field sparrow (Spizella pusilla), prairie warbler (Setophaga discolor), and Bell’s vireo (Vireo bellii). A focus on habitat management and associated monitoring on relatively small (<20,000 acres) areas was shown to be successful on an individual area, as determined by increases in bird numbers across years and challenges completed in the Quail Plan but did not result in an observed increase in statewide quail indices. Future quail restoration plans in Kentucky should be directed more toward open production land, which is made up of 6 million acres of pastureland, hay land, row crop agriculture, reverting fields, reclaimed mineland, and grasslands. This work will be completed by utilizing working lands, such as field borders in row crop systems and grazing native warm-season grasses in pasture or hay systems, for wildlife activities. Monitoring systems on these production lands will be in the breeding season only and autonomous recording devices will be

Behavioral State-Specific Northern Bobwhite Chick Resource Selection

Determining resource selection rates for all life stages of a species is critical to enable a holistic management approach that focuses on bolstering populations across all life stages. Moreover, tying these selection rates to specific life history needs (e.g., foraging, roosting, and loafing) can provide valuable information to guide management practices. Northern bobwhite (Colinus virginianus; hereafter, bobwhite), a gallinaceous species of North America, has experienced steady population declines throughout much of its range over the last 50 years. Although the species has been well studied, chick ecology is still relatively unknown. We studied bobwhite chick resource selection on a private property in Brunswick County, North Carolina, USA to better understand daily and within home range selection. The site was managed intensively for bobwhite using prescribed fire, seasonal mowing and disking, mesomammal control, and supplemental feeding. We radio-tagged 156 chicks 11–15 days of age from 29 unique broods and collected location data for nocturnal roost sites, daily movement tracks, and diurnal use sites during a 2-year span. We had selection models for 3 behaviors: roosting, foraging, and general movements within home range (third-order). All models were mixed-effects conditional logistic regression models under a Bayesian framework. We determined foraging behavior using a straightness index for daily track segments; more tortuous segments were designated as foraging locations. Upland pine stands (burned and unburned) were selected for foraging and roosting. Chicks were more likely to select areas closer to feedlines for roosting, foraging, and diurnal habitat; however, selection of these areas decreased as birds grew older. Chicks avoided fallow fields and hardwood drains or Carolina bays as roost site locations yet selected them as foraging habitat. Roosting birds avoided fallow fields as roost sites and instead selected areas adjacent to them. Probability of use for diurnal and roosting habitat decreased as distance to fallow fields increased. Our study results shed light on how circadian habitat use can vary and illustrate that one specific land cover may not provide ideal diurnal and nocturnal habitat for bobwhite chicks. The results also reinforce the need to provide resources that meet diurnal and nocturnal requirements within biologically reasonable distances from each other.

A Monitoring Program to Evaluate the Coastal Grassland Restoration Incentive Program

The Gulf Coast Joint Venture (GCJV) is a regionally based, biologically driven, landscape-oriented volunteer partnership of private, state, and federal conservation organizations dedicated to the delivery of habitat important to priority bird species. The GCJV partnership’s Coastal Grassland Restoration Incentive Program (C-GRIP) provides financial incentives to private landowners for conducting habitat treatments that address the greatest limiting factor(s) to providing suitable grassland bird habitat on their property. The C-GRIP program is a way for the GCJV to deliver bird habitat to meet planning objectives for grassland birds, including northern bobwhite (Colinus virginianus). Our monitoring objective is to evaluate whether the C-GRIP program is effective in providing a relative increase in the density (number/acre) of priority grassland bird species in focal delivery areas versus control areas over a 10-year period. Twenty survey routes (2 within each of 5 focal areas and 2 outside of each area, serving as controls), located on secondary and tertiary roads, were designated in the Texas Mid-Coast Initiative Area of the GCJV. Each route is 15 miles long and the land cover is similar along all survey routes. Each route has ≥30 point-count stations separated by ≥0.5 mile. We recognize that some routes will experience increased development over time, especially in counties neighboring large population centers such as Houston and Victoria. The plan is to continue to monitor these routes, as long as safety concerns do not increase. Survey data will be analyzed using Program Distance 7.3, release 1. Our poster will include details about the monitoring objective, survey route selection, and survey methods.

Translocating Wild California Valley Quail to Texas: An Evaluation of Survival, Dispersal, Tracking Efficacy, and Roost Preference

Quail translocations are becoming increasingly popular in regions of suitable habitat where local quail populations have declined. In northeastern Texas, USA, northern bobwhite (Colinus virginianus) populations have drastically declined for over a century and have reached undetectable levels in many areas. As a result, the number of quail hunters and quail conservation funding have also declined. California valley quail (Callipepla californica; hereafter, valley quail) have increased across their range and have been translocated to many states and countries. Thus, the goal of this study was to determine whether translocating wild valley quail to Texas was feasible, and evaluate their survival, dispersal, roost location preference, and potential predator impacts. We translocated 748 wild valley quail from Idaho, USA to northeastern Texas in 2019 and 2020. We collected quail location data from very high frequency (VHF) and digital transmitters. Motion-triggered cameras, scent stations, simulated nests, and raptor transects were used to record predator presence and potential predator impacts. Survival of birds with tracking devices was 63% (VHF) in 2019, and 38.8% (VHF) and 92.5% (digital tag) in 2020. Survival was greater for quail with digital transmitters. Median dispersal distance was 633.5 m in 2019 and 246.6 m in 2020 for valley quail with VHF transmitters, and 310.4 m for quail with digital transmitters. Minimum convex polygon area medians were 4.3 ha in 2019 and 3.1 ha in 2020 for quail with VHF transmitters, and 16.1 ha in 2020 for quail with digital transmitters. Roost sites were primarily in young stands of oak trees. Median simulated nest survival was 2 days (minimum [min] = 1, interquartile range [IQR] = 2–5.4, maximum [max] = 23) in 2019, and 7.5 days (min = 2, IQR = 4.5–15.2, max = 23) in 2020. The most frequent mammalian predators observed were raccoons (Procyon lotor), feral hogs (Sus scrofa), and white-tailed deer (Odocoileus virginianus). Red-tailed hawks (Buteo jamaicensis) were the most frequent aerial predator. We completed the first documented translocation of wild California valley quail to Texas, demonstrating it is feasible. Future translocation may benefit from translocating more birds over a longer period of time, with more consistent methodology. The establishment of a sustainable population may require ≥7 years of translocation at a rate of 500 birds per year with >2,000 ha of suitable habitat.

Adaptive Management Facilitates Increase in Northern Bobwhite Populations

Adaptive resource management (ARM) is an approach to managing that allows decision makers to learn about a system and subsequently change management actions based on new information about system processes (i.e., adapt) to better meet fundamental objectives. This is not to be confused with changing management actions when the state of the system changes. For example, changing a harvest regulation when populations decline is not ARM. This dynamic decision making may be fortuitously optimal, but if the effect of harvest is uncertain then changing regulations may be suboptimal—for example, weather may have caused the decline. Adaptive resource management can be implemented along a spectrum of passive to active to reduce system uncertainty. Active ARM is when explicit hypotheses are posited then implemented to test them, and monitoring occurs to elucidate whether the effect of the management action achieved a given result. Passive ARM uses current management practices, natural variation in the system, and monitoring to reduce uncertainty. Even though northern bobwhite (Colinus virginianus) have been studied for a century, uncertainty regarding optimal management strategies still exists. The Albany Quail Project (AQP) has used both modes of ARM to learn about northern bobwhite populations to better meet the hunting objectives of stakeholders. Between 1992 and 2019 the AQP radio-tagged 5,182 unique individuals and banded an additional 5,008 birds on the primary study area near Albany, Georgia, USA. Additionally, 1,724 nests have been monitored and population surveys conducted in the spring and autumn. Active ARM occurred with tests of supplemental feeding, hardwood cleanup, and predator control whereas passive ARM was used to learn about prescribed fire regimes, brood habitat preferences, small mammal cycles, and raptor migrations. We built an integrated population model (IPM) that combined known-fate survival data, nesting records, dead recoveries from harvest, and population surveys to model the system. The preliminary results of the IPM demonstrated that populations have increased during the project. The 5 most abundant autumn populations have occurred in the most recent 10 years of the project when bobwhite populations throughout their range have continued to decline. Unlike typical ARM applications, the AQP has not had an explicit model to predict consequences of future management actions; nonetheless, the essence of ARM has been followed. Since its inception uncertainty has been reduced, management actions have been changed, and bobwhite populations have responded. Improvements to AQP and similar projects could include explicit hypotheses and predictive models about the system

Evaluation of a Solar-Recharged Micro-GPS Datalogger for Northern Bobwhite in the Rolling Plains of Texas

The use of Global Positioning Systems (GPS) transmitters on northern bobwhite (Colinus virginianus; hereafter, bobwhite) could increase our understanding of fine-scale movements and habitat use for a declining game bird species. We evaluated solar-recharged micro-GPS dataloggers to determine the effectiveness of the units on free-ranging bobwhite and we conducted a controlled experiment to determine the accuracy of the dataloggers under a variety of canopy cover. We deployed the micro-GPS dataloggers on 25 bobwhites between August 2016 and April 2017 across 4 different ranches in the Rolling Plains of West Texas, USA. Accuracy (± standard error) for the 8 dataloggers across 3 trials for the stationary tests was 25.4 ± 3.8 m. Daily movement of bobwhite averaged 0.96 ± 0.09 km and morning movements averaged 0.49 ± 0.07 km. Average 95% and 50% minimum convex polygons for bobwhite area utilization were 15.2 ha and 3.6 ha, respectively. Our data indicate that solar-recharged micro-GPS dataloggers can be used to monitor bobwhites’ short-term fine-scale movements in West Texas.

Survival, Movement, and Habitat Use of Translocated Northern Bobwhite in Texas

For decades there has been a noticeable decline in northern bobwhite (Colinus virginianus; hereafter, bobwhite) populations. Few studies have assessed the survival of translocated bobwhite. We evaluated the effectiveness of reintroduction of bobwhite into the Texas (USA) Parks and Wildlife Department’s Gus Engeling Wildlife Management Area (GEWMA), where they had been extirpated but now have suitable habitat. Before reintroduction, GEWMA was surveyed (spring call counts) to make sure no bobwhite were present. Forty-six bobwhite were trapped from March–April 2019 in South Texas, banded, bled, radio-tagged, transported to GEWMA, and released. In addition, 17 bobwhite were trapped banded, bled, radio-tagged, and released back into the source population as a control for comparison of movements, reproduction, and survival estimate differences between the source and released bobwhite populations. During July 2019, 3 broods (24 bobwhite) were trapped and translocated from a South Texas ranch to the GEWMA. Survival for bobwhite released at GEWMA was 37.0% through 1 July 2019 and 70.6% for bobwhite left on the ranch in South Texas. Three nests were found at GEWMA while none were found on the ranch in South Texas. Movement distances between daily locations for males and females did not differ at GEWMA or at the ranch in South Texas; however, there was a significant (P ≤ 0.001) difference in daily movement for bobwhite at GEWMA and the South Texas ranch. Female bobwhite at GEWMA moved 5.4 times the distance of female bobwhite in South Texas and male bobwhite at GEWMA moved 5.9 times the distance of male bobwhite in South Texas. Bobwhite at GEWMA were located in woody cover only 24.2% of the time, whereas bobwhite in South Texas were located in woody cover 76.1% of the time. The greater daily movement and less use of woody cover for bobwhite at GEWMA probably contributed to their lower survival.

Northern Bobwhite Response to Vegetation Management and Recovery in South Texas

The northern bobwhite (Colinus virginianus; hereafter, bobwhite) requires habitat structure and composition with grass cover for nesting, predator avoidance, and thermal refuge and forb cover for feeding on phytophagous arthropods and seeds. During the past 2 decades, many land managers with interest in promoting quail hunting opportunities have reduced or completely eliminated livestock across South Texas, USA, rangelands. Resting the land from grazing allows vegetation—especially grasses and forbs—to recover and thus provide nesting and foraging habitat for bobwhite and other birds. How bobwhite respond to postgrazing vegetation recovery is of keen interest to rangeland quail managers, but this topic is poorly known because case histories with quantitative data are lacking. Our objective was to investigate how bobwhite respond to the vegetation changes following removal of cattle grazing. Our study was conducted on a private ranch in Jim Hogg County, Texas and involved 3 different categories of postgrazing recovery and management: 1 area at 15 years post-cattle grazing where the landscape has been brush-sculpted and is actively managed since removal of cattle, 1 area at 3 years post-grazing with a previous stocking density of 7 ha/animal unit (high stocking density), and 1 area at 3 years post-grazing with a previous stocking density of 14 ha/animal unit (moderate stocking density). We trapped, radio-marked, and located bobwhites from March to September during 2015–2016 on the 3 comparative units. We estimated nest survival, adult breeding-season survival, home range size, and early winter density. We hypothesized that the 15-year postgrazing site would have higher early winter density, higher adult breeding season survival, and higher nest survival along with smaller mean home range size compared to the 2 more recently grazed sites. On average, the probability of a nest surviving the 23-day incubation period was highest on the 15-year postgrazing site at 0.61 ± 0.12 (mean nest survival ± standard error), with estimates of 0.32 ± 0.12 on the 3-year moderate postgrazing site and 0.33 ± 0.12 on the 3-year high postgrazing site. Adult breeding season survival did not differ among the 3 sites, and was instead influenced mostly by month within the season, probably a result of summer heat. An adult bobwhite had a 0.48 ± 0.04 probability of surviving the breeding season. Early winter density, after summer and fall production was complete, increased on all sites from 2015 to 2016 and was consistently highest on the 15-year postgrazing site. Home range sizes on the

Winter Survival and Resource Use of Translocated Northern Bobwhite in the Mid-Atlantic United States

Northern bobwhite (Colinus virginianus; hereafter, bobwhite) in the Mid-Atlantic United States have been experiencing precipitous population declines due to a combination of habitat deterioration, urban and suburban sprawl, change in forest management regimes, and farming practices. In recent years, restocking of bobwhite through translocation efforts has gained interest to rebuild local populations. However, empirical studies are warranted to understand the limitations of translocation as it relates to its potential use for long-term population recovery and persistence in this region. Further, few studies nation-wide have evaluated resource use and survival during the non-breeding season on translocated sites. As such, we translocated 360 bobwhites from source populations from southern latitudes during March–April 2015–2017 into 2 different landscape types similar to the source population vegetative communities (agricultural cropland dominated in Maryland, USA versus pine forest dominated in New Jersey, USA) and tested the effects of habitat fragmentation on survival and habitat use during the subsequent non-breeding season. We found habitat fragmentation negatively affecting survival and resource use among translocated bobwhite on fragmented cropland-dominated sites as compared to larger unfragmented forested sites. Survival was lower on cropland sites compared to forested sites such that bobwhite in cropland-dominated landscapes were >125 times less likely to survive the winter than those on forested sites. In our examination of resource use, bobwhite in structurally complex forested sites used cut pine, early-successional woody, early-successional herbaceous, and thinned pine more than what was available on the landscape. On the cropland sites bobwhite used food plots, early-successional woody, and mixed woods more than what was available on the landscape and only food plots at the home range scale. While larger unfragmented forested bobwhite habitat ultimately provided a more successful translocation landscape, birds still had large home ranges and relatively low survival. Therefore, proper pine management may be necessary to optimize habitat availability during the non-breeding season. Our findings provide rare information on demographic resiliency and resource use for translocated bobwhite during the non-breeding season. Further, this research provides valuable information to improve future translocation efforts in the Mid-Atlantic.

Northern Bobwhite Response to Control of Red Imported Fire Ants in the Gulf Coast Prairie of Texas

The population decline of northern bobwhite (Colinus virginianus; hereafter, bobwhite) on the Texas Gulf Coast Prairie, USA is largely attributed to habitat loss. However, red imported fire ants (Solenopsis invicta) occur throughout the region and are considered a possible contributing factor to the bobwhite decline. The objectives of our study were to determine the influence of red imported fire ants on bobwhites by comparing bobwhite nest success, survival, and density between sites treated with fire ant bait (treatment) and reference (control) sites. Our study was conducted on 3 private ranches in Goliad and Refugio counties, Texas. Each ranch contained 2 paired experimental units that consisted of a treatment and control site (500 ha each). The treatment sites received an aerial application of fire ant bait (Extinguish® Plus) during April 2018, whereas the control sites were not treated. We estimated mound density by counting fire ant mounds using distance sampling. We used radio-telemetry to monitor bobwhite nest success and survival, and we estimated bobwhite densities using distance sampling via helicopter surveys. Fire ant mound density decreased through time on both treatment and control sites. However, fire ant mound density was lower on treatment sites than control sites, indicating the insecticide was effective at decreasing fire ant mound density. Bobwhite survival, nest success, and density did not statistically differ between control and treated sites either pre-treatment (2017) or post-treatment (2018), but survival and nest success metrics were numerically higher in treated units. Bobwhite survival remained relatively stable in the treatment units 4 weeks after application but decreased in the control units. Following treatment, apparent nest success in the treated units increased by 37.4% while nest success in the control units decreased by 35.2%. Bobwhite populations were low in this ecoregion, which influenced our ability to trap and monitor many bobwhites or monitor many nests. In addition, it may be possible that repeated, annual treatments for fire ants are necessary for a benefit to accrue and be observed in bobwhites. Our results indicate that there may be potential benefits to bobwhites from fire ant reduction that deserve further research attention.

Impacts to Quail Space Use and Demographics from Oil and Gas Development

Southern Texas contains some of the last relatively unfragmented habitat for northern bobwhite (Colinus virginianus; hereafter, bobwhite) and scaled quail (Callipepla squamata) in the United States. Development of the Eagle Ford Shale hydrocarbon formation in this region could negatively impact quail and their habitat. Our objective was to examine the indirect effects of oil and gas activity (traffic and noise) on bobwhite and scaled quail on 2 private ranches in southern Texas. In 2015 and 2016, we radio-marked bobwhite and scaled quail in 2 areas where oil and gas activity was occurring (disturbed treatment) and 2 areas where little oil and gas activity occurred (undisturbed treatment). We measured vehicle passages and modeled noise propagation from oil and gas infrastructure at 2 biologically relevant frequencies (250 Hz and 1,000 Hz) in our study area to quantify oil and gas disturbance and examine its effects on quail space use (site selection and home range size) and demographics (survival, nest success, and density). Bobwhite and scaled quail selected areas 0–200 m and >425 m, respectively, from the primary, high-traffic roads in the disturbed treatment. In the undisturbed treatment, bobwhite and scaled quail selected areas 0–425 m and 0–300 m from primary roads, respectively. Bobwhite and scaled quail selected areas with sound levels 0–1.6 and 0–2.2 dB above ambient levels at the 250-Hz frequency level, respectively. At 1,000 Hz, bobwhite and scaled quail selected areas with sound levels 0–2 and 0–3.2 dB above ambient levels, respectively. We found no evidence that disturbance variables affected bobwhite and scaled quail home range size, survival, or density. We found bobwhite nest success decreased as sound levels (dB) at 250 Hz increased; we found no relationship between nest success and disturbance for scaled quail, possibly as they avoided major oil and gas disturbances. In calculations of the total footprint of quail habitat loss, indirect loss due to oil and gas activity needs to be considered in addition to direct loss due to conversion of rangeland to oil and gas infrastructure.

Examining a Habitat-Weather Threshold for Northern Bobwhite Populations in the Southwestern United States

In semiarid portions of the northern bobwhite (Colinus virginianus; hereafter, bobwhite) geographic distribution, weather is a strong driver of interannual abundance. However, the strength of this relationship may depend on habitat amount. Given this habitat–weather dependence, there is likely to be a threshold value for habitat that determines how strongly a bobwhite population responds to weather. Our objective was to evaluate the relationship between habitat amount and the relative influence of weather on bobwhite abundance in Texas and Oklahoma, USA and determine a potential land-cover threshold value. We collected bobwhite abundance and land-cover data from the Breeding Bird Survey and National Land Cover Database, respectively, for 2 time periods which corresponded to historical lows (2012–2013) and highs (2015–2016) of bobwhite abundance within this region. We reclassified land cover into grassland, shrubland, pastureland, cropland, forest, and urban cover, and combined grassland and shrubland categories to represent bobwhite habitat. We used weighted linear regression to model the difference between mean bobwhite abundance between each time period as a function of habitat amount, hypothesizing a positive, linear relationship given the theorized greater influence of weather on populations within higher habitat amounts. To evaluate a potential habitat threshold, we modeled mean bobwhite abundance, for each time period, and all individual land-cover variables using a generalized additive model with a negative binomial distribution. We detected a positive, linear relationship between habitat amount and the difference between high and low bobwhite populations (r2 = 0.30), per our hypothesis. Models of land-cover variables differed between low- and high-abundance time periods. The time period of lower abundance (2012–2013) model included all land-cover variables except cropland and showed significant positive, linear relationships with grass and hay cover, and negative, linear relationships with forest and urban cover. Shrubland cover was the only nonlinear term, increasing to approximately 50–60% cover, then decreasing sharply with increasing cover. Deviance explained for this model was 41.2%. For the period of high abundance (2015–2016) the model explained approximately 25% of the deviance and was reduced to only negative, linear relationships with forest and urban cover. Our results provide some evidence toward the habitat–weather threshold hypothesis. Additionally, while no land-cover values showed a threshold-like relationship with bobwhite abundance, we did document differences in variable selection for each time period. Stressors on bobwhite habitat seem to have a more dramatic impact on bobwhite populations than available habitat, especially in periods of higher abundance, whereas periods of lower

Breeding Season Survival and Reproduction in a High-Density Bobwhite Population: A case study

The demographic behavior of northern bobwhite (Colinus virginianus; hereafter, bobwhite) populations at high densities could provide important insights into why bobwhite populations fluctuate. Therefore, we documented breeding season demographics of bobwhites to understand how prebreeding density influenced reproductive effort and postbreeding density on an intensively managed property in Leon County, Florida, USA, 2002–2006. We estimated prebreeding bobwhite density each April using multi-observer strip-transects and postbreeding densities each November using covey call grid surveys. We radio-tagged 217 bobwhites in March and located bobwhites at least 5 days/week, 15 April–30 September to determine vital rates. Prebreeding density ranged from 1.5–8.6 birds/ha, peaking in 2002, declining through 2005, then increasing in 2006. Breeding season survival was 0.55, 0.17, 0.20, and 0.59, and nesting rate was 0.47, 0.67, 0.80 and 0.89, 2002–2005, respectively. Postbreeding density ranged from 5.2–13.6 birds/ha, also peaking in 2002 and declining through 2004 before increasing beginning in 2005 and 2006. High breeding season survival and nesting success (>0.55) resulted in greater chick production during periods of population growth. Nesting rate was inversely related to prebreeding density. Declines in bobwhite nesting rate at high prebreeding densities appeared to regulate population growth near population peaks. Lower adult survival and nesting success appeared to cause population declines. We suggest density-dependent intraspecific competition limited population growth at high bobwhite densities by reducing nesting rate while predation of adults and nests explained population fluctuations.

Northern Bobwhite Survival and Productivity in Relation to Food Supplementation

Northern bobwhite (Colinus virginianus; hereafter, bobwhite) populations have experienced a 3.4% decline annually nation-wide from 1966 to 2018. Limitations on resources, such as food, can regulate population growth. Supplemental food could alleviate resource limitation by raising carrying capacity, leading to increased survival and breeding productivity. Studies have shown higher survival rates and higher nest production when food is supplemented; however, repeating experiments in different contexts allows for strong inference. Our objectives were to assess how supplemental food influenced survival and breeding productivity of resident and translocated bobwhite during a 2-year study on public lands in Leon County, Florida, USA within the Apalachicola National Forest. In accordance with the food limitation hypothesis, we predicted that provisioning of supplemental food would have a positive influence on survival rates and nest productivity. We split the study site into 4 approximately 400-ha zones and randomly assigned 2 treatment (fed) and 2 control (unfed) replicates. Treatment and control zones were flipped during the second field season. Treatments received approximately 1.75 bushels of milo (Sorghum bicolor)/acre 2 times/month year-round via broadcast spreader. We radio-marked 205 bobwhites (102 treatment, 103 control) from February 2019 through October 2020. Individuals were tracked 3–4 times/week for location and survival via radio-telemetry to estimate the breeding season survival and reproduction rates. We estimated survival rates using the Kaplan-Meier product limit estimator. The survival rate during the breeding seasons was higher on average for treatment zones (x̄ = 0.38, standard error [SE] = 0.040) than for control zones (x̄ = 0.29, SE = 0.045). We also observed that 79% of nests found were located in treatment zones compared to 21% in control zones. Our results suggest that food supplementation can improve survival rates and nest production of bobwhite in a food-limited landscape.

Examination of an Anecdotal “October Disappearance” of Northern Bobwhite in the Rolling Plains of Texas Through Demographic Data

Landowners and wildlife managers in the Rolling Plains ecological region of Texas, USA often report encountering northern bobwhite (Colinus virginianus; hereafter, bobwhite) in summer but observe what they perceive as a decrease in quail by early to mid-fall. As most bobwhite research in the Rolling Plains is focused on either breeding season or overwinter survival and movement, researchers rarely record demographic data during this late summer and early fall period. We examined weekly survival probabilities of bobwhite (n = 244) across 7 sites in the western Rolling Plains Ecoregion from August to late November in 2016, 2017, 2019, and 2020. Bobwhites were captured and equipped with very high frequency (VHF) transmitters and tracked 1–5 times/week. We used Akaike’s Information Criterion adjusted for small sample sizes (AICc) to evaluate a suite of candidate models comparing survival among and between years and survival between individual weeks to determine whether an unreported population decrease occurred during the study years. Our comparison of weekly survival probabilities considered survival to be different if 95% confidence intervals did not overlap. Our best supported model held survival constant among years and allowed survival to vary week by week. All other models received little support (ΔAICc > 14.0). Examination of weekly survival probabilities failed to support a demographically driven hypothesis for decreased bobwhite observations from August to November. Though there was an observed decrease of weekly survival in the fourth week of September, it was not different than 16 of the 17 other weeks. We conclude that, for the years we measured, there was no support for a mass die-off hypothesis. Factors outside survival (e.g., a change in bobwhite behavior) may be driving the difference in detectability between late summer and late fall in the Rolling Plains of Texas.

Bobwhite Response to Cattle Grazing in South Texas

Range management practices to improve habitat for wildlife by reducing brush and increasing herbaceous plants, coupled with reduced stocking rates, can lead to dense stands of dominant grasses, such as four-flower trichloris (Trichloris pluriflora). This monoculture of trichloris creates dense vegetation unsuitable for northern bobwhite (Colinus virginianus; hereafter, bobwhite), reduces plant species diversity, and alters ecosystem functions. The objectives of this study are to 1) evaluate the effects of a proper cattle grazing regime to improve bobwhite habitat and 2) develop a management guide documenting how cattle grazing can be used as a tool to reduce the density and cover of dominant grasses and thereby allow higher plant species richness. The study is taking place in Duval County, Texas, USA, between 2 pastures with a combined area of 2,500 ha. One pasture serves as the control (1,337 ha) while the other (1,109 ha) is grazed to maintain a stubble height of 30–40 cm. We placed 10 grazing exclosures and 10 25-m transects within each treatment to determine botanical composition and cover. Double sampling is conducted monthly to determine forage standing crop. Forage standing crop, plant species richness, total ground cover, and forage utilization will be estimated. We hypothesize that 1) the grazed pasture will contain more bobwhites than the nongrazed pasture, 2) plant species richness will be greater in the grazed pasture, and 3) grazing will reduce the cover of trichloris. In 2020, plant species richness varied among sampling periods and was recorded as 7.5 species/transect and 4.8 species/transect higher in the nongrazed control compared to the grazed pasture in June and August, respectively. After the end of the first year of grazing, however, there was no statistical difference in plant species richness between the 2 pastures, a result that does not coincide with our second hypothesis. Litter cover did not vary among sampling periods in the nongrazed pasture but changed in the grazed pasture. Litter cover was 9.4%, 14.3%, 14.6%, and 8.9% higher in the grazed pasture than in the nongrazed pasture in May, August, September, and December 2020, respectively. Bare ground cover changed throughout sampling periods in the nongrazed and grazed pastures. Bare ground cover was 22%, 18%, and 22% higher in the grazed pasture than in the nongrazed pasture in May, September, and December 2020, respectively. Trichloris cover did not change throughout the sampling period in the grazed pasture but varied in the nongrazed pasture. Trichloris cover

Diurnal Occurrence of Great-Horned Owls on Northern Bobwhite Hunting Properties in Southwest Georgia

Understanding interactions between prey species and their predators is essential to discerning the ecology and management fundamentals of a species. Great-horned owls (Bubo virginianus) have long been considered an opportunistic predator of northern bobwhite (Colinus virginianus; hereafter, bobwhite) and recent studies have demonstrated that bobwhite survival is reduced at higher great-horned owl densities (Rectenwald et al. 2021). Managers on quail properties often mechanically remove live oak (Quercus virginiana) hammocks as part of larger predation management plans to reduce the amount of suitable predator habitat. While scattered live oaks are typically left for aesthetic purposes, these serve as preferred day roosts and hunting perches for great-horned owls. To improve bobwhite survival and fitness, managers on quail properties broadcast supplemental grain along designated trails at a density of 2.4 km/40.5 ha of upland habitat. From the peak of bobwhite brooding season to the end of the breeding season (i.e., Jun–Sep), it is common for managers to switch from broadcasting grain from feed trails to broadcasting grain from mowed roads to reduce tractor activity in obscured cover where broods or nests may be run over and destroyed. Bobwhite are potentially at higher risk for predation where live oak hammocks are intersected by feed trails due to increased exposure time in areas with higher predator occurrence. Additionally, bobwhite may be at higher predation risk when feeding on mowed roads in the summer, particularly when in close proximity to live oaks, due to the lack of screening cover from opportunistic owls perched above. We evaluated the probability of use for great-horned owls in relation to live oak hammocks, feed trails, and roads that are fed in the summer. We compared use versus availability for landscape features using a resource selection function in a Bayesian framework. As part of a larger study detecting all raptors that were threat-specific to bobwhite, driving surveys using line-transect distance sampling on a 32.2-km route were conducted twice per month from September 2014–December 2020 between 0800–1000 at a speed of 16 km/hr. The surveys encompassed a 5,400-ha privately owned property in Baker County, Georgia, USA. Surveys were conducted only on days with fair weather (i.e., no fog or rain). When great-horned owls were visually detected, their location was recorded on a Global Positioning System (GPS). Great-horned owl density on the property averaged approximately 0.86 owls/km2 during the bobwhite breeding season and 0.58 owls/km2 in the non-breeding season (Rectenwald et al. 2021).

Are northern bobwhites an umbrella species for open‐land birds in Ohio?

AbstractBirds that inhabit open lands such as grasslands and shrublands are rapidly declining across North America. A common practice for multi‐species management is to focus on umbrella species whose habitat requirements overlap with several other species. We evaluated whether the northern bobwhite (Colinus virginianus; bobwhite) could serve as an umbrella species for open‐land birds in Ohio, USA. We related landscape metrics to abundance patterns and assessed whether bobwhite occupancy positively predicts presence of open‐land birds. We combined bird survey data from the second Ohio Breeding Bird Atlas (2006–2011) with land cover data from the 2011 National Land Cover Database (Homer et al. 2015) to construct single‐season N‐mixture models to identify landscape metrics that influence bobwhite abundance. Bobwhite abundance was positively predicted by forest cohesion, percent agriculture, percent barren, and percent grassland. Of the 34 focal species, bobwhites were a significant positive predictor for 12, and a significant negative predictor for 10. The model with only bobwhite occupancy probability as a predictor was the best supported model for only willow flycatcher (Empidonax traillii). These results suggest that bobwhite land cover type requirements are too specialized to meet the needs of broader species guilds, instead affording protection for a narrower range of individual species that share specific habitat requirements with bobwhites. Management for bobwhites may still be able to promote co‐occurrence for declining species across multiple guilds by identifying locations where focused management can create more suitable conditions for species with positive co‐occurrence.

Ecotoxicological QSTR and QSTTR Modeling for the Prediction of Acute Oral Toxicity of Pesticides against Multiple Avian Species.

The ever-increasing use of pesticides in response to the rising agricultural demand has threatened the existence of nontarget organisms like avian species, disrupting the global ecological integrity. Therefore, it is critical to protect and restore different endangered bird species from the perspective of ecosystem safety. In the present work, we have developed regression-based two-dimensional quantitative structure toxicity relationship (2D QSTR) and quantitative structure toxicity-toxicity relationship (QSTTR) models to estimate the toxicity of pesticides on five different avian species following the Organization for Economic Co-operation and Development (OECD) guidelines. Rigorous validation has been performed using different statistical internal and external validation parameters to ensure the robustness and interpretability of the developed models. From the developed models, it can be stated that the presence of electronegative and lipophilic features greatly enhance pesticide toxicity, whereas the hydrophilic characters are shown to have a detrimental impact on the toxicity of pesticides. Moreover, the developed QSTTR models have been employed to the in silico toxicity prediction of 124, 154, and 250 pesticides against bobwhite quail, ring-necked pheasant, and mallard duck species, respectively, extracted from the Office of Pesticides Program (OPP) Pesticide Ecotoxicity Database. The information obtained from the modeled descriptors might be used for pesticide risk assessment in the future, with the added benefit of providing an early caution of their possible negative impact on birds for regulatory purposes.