Usable space and mircohabitat characteristics for bobwhites on private lands in southwestern Ohio
Mark J. Wiley, MS
Advisor: Robert J. Gates
Habitat loss due to intensified agriculture, forest maturation, and urbanization is widely accepted as the primary cause of range-wide northern bobwhite (Colinus virginianus) population declines. Although much is known about bobwhite habitat associations, management efforts have failed to halt the decline in most states. Some suggest that bobwhite habitat management has not occurred at the appropriate scale to mitigate the negative impact of changing landscapes. To evaluate the landscape suitability for bobwhites in the core of their range in Ohio, I used radio-telemetry to quantify usable space at various temporal and spatial scales on four private land study sites in southwestern Ohio during 2009-2011. To investigate habitat suitability at a fine-scale, I compared structural and compositional measurements from used and unused winter microhabitats. Mean annual usable space estimates ranged from 10.3% to 24.4% for the four sites. Amount of usable space decreased considerably during the non-breeding season due to increased preference for more limited cover types during that period. Covey density ranged from 0.0580-0.2109 coveys per hectare of usable space during the non-breeding season. Analyses of inter-patch distance of cover types suggested that there is a complex interplay of at least three important cover types influencing use on these sites. Predicted probability surfaces showed considerable variability in amount and distribution of areas of high predicted use among sites. Horizontal visual obstruction (≤ 1.05 m height) was the most important predictor of microhabitat use across all cover types. Canonical correspondence analysis identified several plant species associated with use. The primary focus of bobwhite management should be increasing usable space based on the composition and inter-patch distance of key cover types. Within landscapes considered suitable for bobwhites in Ohio, habitat management should focus on improving low-level structural complexity, thereby improving the capacity of cover to conceal and protect bobwhites during winter.