Demographic Sensitivity of Population Change in Northern Bobwhite

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.     

THE EFFECT OF MOLLUSCICIDES ON THE CONSUMPTION OF BAIT BY SLUGS

The consumption of bait by Agriolimax reticulatus and Milaxbudapestensis has been measured. Although the addition of methiocarbto the bait may reduce the numbers of Milax which eat it, themain effect of adding poison is to reduce markedly the amountof bait consumed. This effect is discussed in relation to thepoison concentration in the bait, the consequent ingestion ofpoison, and the cause of the reduction. (Received 11 September 1979;     

Effect of environmental conditions during the larval period on the tendency of worker honeybees to develop their ovaries

An account is given of the effect of rearing honeybees in queenless and queenright colonies on their ovary development.