Survival and Causes of Mortality for Northern Bobwhites in the Southeastern USA

Abstract

Long-term studies are imperative to increase our knowledge of northern bobwhite (Colinus virginianus; hereafter bobwhite) demographics. During 1992-2005, we determined survival and cause-specific mortality of bob-whites on 10 study areas in southern Georgia and eastern Alabama, USA. We radio-tagged 7,105 bobwhites and determined 49 annual (Oct-Sep) and 110 seasonal survival estimates to examine spatial and temporal variation in survival. Annual survival for all sites and years combined averaged 0.196 (SE = 0.011) and ranged from 0.08 to 0.40. Over-winter (Oct-Mar) seasonal survival estimates (n = 51) averaged 0.541 (SE = 0.019) and ranged between 0.25 and 0.82, while breeding season (Apr-Sep) survival estimates (n = 59) averaged 0.352 (SE= 0.013) and ranged between 0.13 and 0.59. Over-winter mortality (n = 1,473) of known fates was attributed to avian predation (0.572 ± 0.040), mammal predation (0.265 ± 0.044), harvest (0.156 ± 0.028), snake predation (0.001 ± 0.004) and other (0.005 ± 0.002). Breeding season mortality (n = 2138) was attributed to avian predation (0.613 ± 0.026), mammal predation (0.339 ± 0.049), snake predation (0.037 ± 0.006) and other (0.011 ± 0.004). These over-winter survival estimates were higher than previously published estimates for populations on un-managed lands and/or heavily harvested populations. On managed lands in the Southeast, bobwhite annual survival rates derived from radio-telemetry were reasonable and provided useful information for management and research. Citation: Sisson DC, Terhune TM, Stribling HL, Sholar JF, Mitchell SD. 2009. Survival and causes of mortality for northern bobwhites in the southeastern USA.