Northern bobwhite select for shrubby thickets interspersed in grasslands during fall and winter.

Abstract

Resource selection is a key component in understanding the ecological processes underlying population dynamics, particularly for species such as northern bobwhite (Colinus virginianus), which are declining across their range in North America. There is a growing body of literature quantifying breeding season resource selection in bobwhite; however, winter information is particularly sparse despite it being a season of substantial mortality. Information regarding winter resource selection is necessary to quantify the extent to which resource requirements are driving population change. We modeled bobwhite fall and winter resource selection as a function of vegetation structure, composition, and management from traditionally (intensively) managed sites and remnant (extensively managed) grassland sites in southwest Missouri using multinomial logit discrete choice models in a Bayesian framework. We captured 158 bobwhite from 67 unique coveys and attached transmitters to 119 individuals. We created 671 choice sets comprised of 1 used location and 3 available locations. Bobwhite selected for locations which were closer to trees during the winter; the relative probability of selection decreased from 0.45 (85% Credible Interval [CRI]: 0.17-0.74) to 0.00 (85% CRI: 0.00-0.002) as distance to trees ranged from 0-313 m. The relative probability of selection increased from near 0 (85% CRI: 0.00-0.01) to 0.33 (85% CRI: 0.09-0.56) and from near 0 (85% CRI: 0.00-0.00) to 0.51 (85% CRI: 0.36-0.71) as visual obstruction increased from 0 to 100% during fall and winter, respectively. Bobwhite also selected locations with more woody stems; the relative probability of selection increased from near 0.00 (85% CRI: 0.00-0.002) to 0.30 (85% CRI: 0.17-0.46) and near 0.00 (85% CRI: 0.00-0.001) to 0.35 (85% CRI: 0.22-0.55) as stem count ranged from 0 to 1000 stems in fall and winter, respectively. The relative probability of selection also decreased from 0.35 (85% CRI: 0.20-0.54) to nearly 0 (85% CRI: 0.00-0.001) as percent grass varied from 0 to 100% in fall. We suggest that dense shrub cover in close proximity to native grasslands is an important component of fall and winter cover given bobwhite selection of shrub cover and previously reported survival benefits in fall and winter.