Survival and Cause-Specific Mortality of Northern Bobwhite in Missouri

Efforts to understand fluctuations in northern bobwhite (Colinus virginianus) abundance illustrate inadequate knowledge of demographic processes. Therefore, we estimated seasonal survival, annual survival, and cause-specific mortality of 1,001 radio-marked bobwhite in northern Missouri. Annual survival was 5.3 ± 0.5% and did not differ between ages (P = 0.33) or sexes (P = 0.48). Fall-spring survival (15.9 ± 0.8%) was less than spring-fall survival (33.2 ± 2.7%, P < 0.001). Females had lower fall-spring survival (13.7 ± 1.1%) than males (17.6 ± 1.1%, P = 0.02). Male-biased sex ratios likely result from differential fall and winter survival. Avian (28.7%) and mammalian (25.7%) predators were primary natural mortality agents. Hunter-retrieved (22.9%) and -unretrieved (5.3%) kill resulted in 28.2% harvest-related mortality. During springfall, males experienced higher avian mortality (26.5%) than females (20.0%) (P = 0.09). Greater vulnerability of males to avian predators may represent a cost of displaying. Each incubation and brood-rearing attempt reduced survival by 16% when compared with nonreproductively active birds during a similar period. Bobwhites must be highly productive to replace annual population losses.