Demographic Sensitivity of Population Change in Northern Bobwhite |
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Authors: | BRETT K. SANDERCOCK WILLIAM E. JENSEN CHRISTOPHER K. WILLIAMS ROGER D. APPLEGATE |
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Affiliation: | 1. Department of Biological Sciences, Campus Box 4050, Emporia State University, Emporia, KS 66801, USA;2. Department of Entomology and Wildlife Ecology, 253 Townsend Hall, University of Delaware, Newark, DE 19716, USA;3. Tennessee Wildlife Resources Agency, Ellington Agricultural Center, Post Office Box 40747, Nashville, TN 37204, USA |
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Abstract: | Abstract: The northern bobwhite (Colinus virginianus) is an economically important gamebird that is currently undergoing widespread population declines. Despite considerable research on the population ecology of bobwhites, there have been few attempts to model population dynamics of bobwhites to determine the contributions of different demographic parameters to variance of the finite rate of population change (Λ). We conducted a literature review and compiled 405 estimates of 9 demographic parameters from 49 field studies of bobwhites. To identify demographic parameters that might be important for management, we used life-stage simulation analyses (LSA) to examine sensitivity of Λ to simulated variation in 9 demographic parameters for female bobwhites. In a baseline LSA based on uniform distributions bounded by the range of estimates for each demographic parameter, bobwhite populations were predicted to decline (Λ = 0.56) and winter survival of adults made the greatest contribution to variance of Λ (r2 = 0.453), followed by summer survival of adults (r2 = 0.163), and survival of chicks (r2 = 0.120). Population change was not sensitive to total clutch laid, nest survival, egg hatchability, or 3 parameters associated with the number of nesting attempts (r2<0.06). Our conclusions were robust to alternative simulation scenarios, and parameter rankings changed only if we adjusted the lower bounds of winter survival upwards. Bobwhite populations were not viable with survival rates reported from most field studies. Survival rates may be depressed below sustainable levels by environmental conditions or possibly by impacts of capture and telemetry methods. Overall, our simulation results indicate that management practices that improve seasonal survival rates will have the greatest potential benefit for recovery of declining populations of bobwhites. |
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Keywords: | Colinus virginianus fecundity life-stage simulation analysis population model quail survival |
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