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Relationships between Selected Population Phenomena and Annual Bobwhite Age Ratios
John L. Roseberry
The Journal of Wildlife Management
Vol. 38, No. 4 (Oct., 1974), pp. 665-673
Stable URL: http://www.jstor.org/stable/3800033
Page Count: 9
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Relationships between fall age ratios of bobwhites (Colinus virginianus) and certain population phenomena are discussed, based on a computer simulation and 17 years of data from the Carbondale Research Area in southern Illinois. Annuial variation in the percentage of juveniles in fall populations on the study area was more strongly correlected with population change from fall to fall and spring to fall than with fall densities per se. Simulation techniques were used to demonstrate the combined effect of changes in proportions of hens successful and survival rates of juveniles and adults on relative population gains from spring to fall. Comparisons were made of the use of young:adult ratios and percentages of juveniles as indicators of these gains. Results of the simulation suggest that variation in juvenile mortality influences percent summer gain more than does variation in adult summer losses. However, the relationship between summer gains and the subsequent percentage of juveniles in the fall is altered by annual variation in adult mortality. In contrast, this relationship is not significantly changed by annual variation in juvenile mortality because the latter exerts an almost equal influence on both relative productivity and fall age ratios. Finally, the relationship between productivity and the proportion of juveniles in the fall is curvilinear, whereas the ratio of juveniles per adult is linearly responsive to productivity, making the latter a preferable index of breeding success.
The Journal of Wildlife Management © 1974 Wiley