Influence of Body Size and Condition on Harvest and Survival of Juvenile Canada Geese

Abstract

Direct recoveries for Canada goose (Branta canadensis interior) goslings from the portion of the Southern James Bay Population (SJBP) on Akimiski Island, Nunavut, Canada, have declined markedly since 1987. We suspected that poor gosling nutrition, due to limited food resources on brood-rearing areas, was causing low survival. Consequently, we measured body size and condition of 2,893 unfledged goslings during late July and early August, 1994-1996. Based on 128 recoveries of dead birds during hunting seasons and 69 recaptures during summer on Akimiski Island, we estimated the separate influences of gosling size and condition on subsequent probabilities of recovery by hunters and survival. Estimated survival probabilities were 0.025, 0.051, and 0.147, and reporting probabilities were 0.0026, 0.0051, and 0.0142 for 1994-1996, respectively. Annual variation in both probabilities was related to size and condition of goslings, which were largest and in the best condition in 1996, followed by 1995, and then 1994. Estimates of slopes suggested that relatively small increases in both body size and condition resulted in increased survival and reporting probabilities. Unlike previous waterfowl research, our results showed that the largest goslings, and those in the best condition, were the most likely to be shot. We suggest that goslings in poor condition died on Akimiski Island before they fledged. We conclude that food availability was limiting recruitment, and predict that harvest restrictions on SJBP Canada geese will not result in an increase in the segment of the population that nests on Akimiski Island.