Habitat Use by Breeding Northern Bobwhites in Managed Old-Field Habitats in Mississippi

To better understand the proximate and ultimate cues associated with habitat selection in breeding northern bobwhites (Colinus virginianus), we compared habitat use vs. availability at 2 spatial scales equivalent to Johnson\u27s (1980) 2nd and 3,d order selection. We conducted the study in managed old-field habitats in Mississippi, from 1994 to 1996. We also estimated habitat use by broods with respect to availability, and quantified micro-habitat characteristics (4th order selection) at brood-rearing sites and nesting sites. Breeding bobwhites did not establish home ranges at random or allocate resources among patches in proportion to their availability. Breeding bobwhites, given a mosaic of seasonally manipulated old-field habitats, consistently used burned fields, disked fields, and areas with advanced woody succession to define breeding season home ranges. Bobwhites allocated their time and resources more to woody areas and fields that had received a combination of burning and disking. Broods consistently used burned/disked fields in proportion to availability; consistently avoided row crops and pastures; and generally preferred woody corridors. Vegetation characteristics at nest sites did not differ from random sites located within the same patch of habitat. Characteristics among nest sites were similar, yet successful nests were located in the proximity of more bare ground and less litter cover than unsuccessful nest sites. Brood site habitat characteristics were similar to nest sites; however, woody canopy (44.3%) and visual obstruction readings (59.0cm) at brood sites were significantly greater than nest sites (26.6% and 32.5cm)

Effects of Radio-Transmitters on Body Condition, Harvest Rate, and Survival of Bobwhites

Numerous studies of northern bobwhite (Colinus virginianus) population and habitat ecology employ use of radio-telemetry techniques to relocate and monitor individuals. Radio-telemetry enables estimation of reproductive success, survival, movements, and home range at levels of resolution not otherwise possible. Unbiased estimation of these parameters via radio-telemetry assumes that survival, reproduction, and behavior of radio-marked individuals are not affected by carrying the radio-transmitter. These assumptions have not been rigorously tested for bobwhites. In 1993, we initiated a study at Divide Section Wildlife Management Area in Mississippi and at Tall Timbers Research Station to test the effects of radio-transmitters on survival, harvest rate, and body condition of bobwhites. From 1993 to 1996 we banded 221 and radio-marked 259 bobwhites on Tall Timbers Research Station. Harvest rate for radio-marked bobwhites was 18.5% and banded birds 12.7%. In 2 of 3 years, radio-marked birds experienced greater mean weight loss between capture and harvest than banded birds. From 1994 to 1995 we radio marked 188 and banded 210 birds on Divide Section Wildlife Management Area. Harvest rate for radio-marked birds was 40% and banded birds 30%. In the 1995-1996 hunting season radiomarked birds had lower mean weight gain from capture to harvest than banded birds. Based on our sample of marked birds, 34% of the fall population on this area was harvested. We have established a captive breeding colony of wild bobwhites at the Blackjack Captive Animal Research Facility at Mississippi State University. During the summer of 1996, genetically wild progeny are being produced to be used in a pen study to evaluate the effects of radio-transmitters on bobwhite body weight and lipid levels under abundant and scarce food resources. This study will provide the first harvest rate estimates for bobwhites on a public hunting area in Mississippi. Additionally, this study will evaluate the effects of radio-transmitters on bobwhite body condition, survival, and harvest rate. It will either validate the assumption of no radio effects and aid interpretation of previous and future radio studies or elucidate critical violations of fundamental assumptions of this methodology. If radio effects are detected, this study will identify the specific mechanisms creating bias in estimation of population parameters. This information will enable researchers to target radio design problems and develop new radio technology with reduced effects. Preliminary results suggest that radio-marking may marginally increase bobwhite vulnerability to harvest and potentially predation

Bobwhite Brood Ecology in Relation to Fallow Field Management Techniques and Prescribed Fire Regime

We used compositional analysis to rank habitats used by nesting and brood-rearing northern bobwhites (Colinus virginianus) in northern Florida. We used a residence index based on brood movement rates and turning angles to predict distribution of organisms among habitat types within brood ranges. We examined relationships among residence indices and vegetation and invertebrate characteristics of the habitat to draw inferences as to brood habitat quality. We related brood survival to vegetation, landscape structure and composition, and invertebrate characteristics within brood ranges. Finally, we reported effects of season of disking (fall vs spring) on vegetative (composition, canopy cover, density, ground cover) and invertebrate (richness and biomass) communities in fallow agricultural fields

Evaluation of Two Marking Methods for 1-day-old Northern Bobwhite Chicks

We compared survival, weight gain, and mark retention of wing bands (n = 50), passive integrated transponders (PITs)(n = 50), and leg bands proportional to the chicks size (control) (n = 50) on 1-day-old northern bobwhite (Colinus virginianus) chicks. A repeated measures, generalized complete randomized block ANOV A of the weekly gain in weight showed no difference in the chicks growth (p \u3e) 0.05). Survival was similar between marking methods (wing band, PITs, leg band, and control). Retention of bands during the twelve-week pen study were equal but 4% of PITs were destroyed when adult birds were recovered after harvest. We concluded that wing bands may be the most practical method of marking 1-day-old bobwhite chicks

Genetic Structure of Northern Bobwhites in Northeast Mississippi and Southwest Tennessee

Precipitous declines in northern bobwhite (Colinus virginianus) populations across most of the natural range may increase susceptibility to genetic isolation, restrict gene flow among subpopulations, and exacerbate vulnerability to catastrophic stochastic processes. We characterized the level of genetic variability of 223 individual bobwhites representing 4 disjunct populations in northeast Mississippi and southwest Tennessee in 2002. Analyses at 8 microsatellite loci suggested observed heterozygosity was lower than expected but showed no significant heterozygosity excess. Estimates of FIS coefficients were positive in each subpopulation, but low overall, suggesting only minor loss in heterozygosity over the entire population. Gene diversity was high and genetic differentiation within and among subpopulations and isolation by distance effects were minimal, suggesting adequate levels of gene flow. We suggest, despite population losses, gene flow is maintained among subpopulations, which may reflect the bobwhite’s ability to disperse successfully in the agricultural landscape in this region. Maintenance of gene flow across seemingly inhospitable landscapes suggests focal area management directives may enhance population sustainability. Greater understanding of the genetic structure of northern bobwhite populations on larger geographic scales and across the species’ range is paramount to population recovery

Relative Invertebrate Abundance and Biomass in Conservation Reserve Program Plantings in Northern Missouri

We measured relative invertebrate abundance, biomass, and diversity in Conservation Reserve Program (CRP) fields planted to red clover (Trifolium pratense)/timothy (Phleum pratense), timothy, orchard-grass (Dactylis glomerata), tall fescue (Festuca pratensis), warm-season grasses (big bluestem [Andropogon gerardi]/switch grass [Panicum virgatum]), orchard-grass/Korean lespedeza (Kummerowia stipu/,acea), and conventionally-tilled soybeans, to assess brood habitat quality for northern bobwhite (Colinus virginkinus). We sampled invertebrate populations by vacuuming along 3 15-m transects (4.56 m2/sample) within 4 fields of each planting type, at 2-week intervals from 1 July to 15 August 1990 and 1991. Invertebrate abundance and biomass were lowest in early August (P \u3c 0.05). The CRP fields planted to a red clover/timothy mixture, and dominated by red clover, had the highest levels of invertebrate abundance and biomass (P \u3c 0.05). Conventionally-tilled soybeans had lower invertebrate abundance and biomass than all CRP covertypes (P\u3c 0.05). Mean invertebrate abundance and biomass in CRP fields were 4 times that of soybean fields. In northern Missouri, CRP fields could provide quality brood habitat if structural characteristics are also consistent with brood foraging needs. Incorporation of a legume in CRP plantings may produce higher invertebrate densities and improve the value of these fields as brood habitat

Seasonal Survival and Cause-Specific Mortality of Northern Bobwhites in Mississippi

Knowledge of northern bobwhite (Colinus virginianus) survival and rates at which specific mortality agents remove individuals from the population is important for implementation of science-based harvest and habitat management regimes. To better understand population response to habitat management, we monitored 194 radio-marked northern bobwhites in managed old-field habitats in eastcentral Mississippi, 1993 to 1996. Bobwhite populations increased during the first 3 years following initiation of disking and burning practices. During the 2nd year of bobwhite habitat management breeding season survival (0.509) was high relative to other southeastern populations. However, breeding season survival declined from the 2nd through the 5th year of management (1993, 0.509; 1994, 0.362; 1995, 0.338; 1996, 0.167; P \u3c 0.001). Declining seasonal survival was attributable to increasing mammalian mortality from 1993 to 1996 (P \u3c 0.01). Avian mortality rates were stochastic and differed among years (P = 0.04), while unknown mortality rates were similar (P = 0.13). Avian mortality evidently operated in a density-dependent fashion, whereas mammalian mortality continued to increase despite declining bobwhite population. Northern bobwhite cause-specific mortality rates among years differed by sex (P \u3c 0.01) and age (P \u3c 0.01). Indices of breeding season relative abundance declined with declining survival. We hypothesize that manipulations (bum, disk, bum/disk) which created habitat that met the seasonal requirements of breeding bobwhites and other early successional prey species, may have resulted in a functional and numerical response of mammalian predators