SURVIVAL AND CAUSE-SPECIFIC MORTALITY OF NORTHERN BOBWHITE IN MISSOURI

Efforts to understand fluctuations in northern bobwhite (Colinus virgi nianus) abundance illustrate inadequate knowledge of demographic proce sses. Therefore, we estimated seasonal survival, annual survival, and cause-specific mortality of 1,001 radio-marked bobwhite in northern Mi ssouri. Annual survival was 5.3 +/- 0.5% and did not differ between ag es (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). Femal es 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 differenti al fall and winter survival. Avian (28.7%) and mammalian (25.7%) preda tors were primary natural mortality agents. Hunter-retrieved (22.9%) a nd -unretrieved (5.3%) kill resulted in 28.2% harvest-related mortalit y. During springfall, males experienced higher avian mortality (26.5%) than females (20.0%) (P = 0.09). Greater vulnerability of males to av ian predators may represent a cost of displaying. Each incubation and brood-rearing attempt reduced survival by 16% when compared with nonre productively active birds during a similar period. Bobwhites must be h ighly productive to replace annual population losses.