Comparisons of body reserve buildup and use in several groups of Canada geese

Abstract

Changes in proximate body composition were analyzed in nonmigratory giant Canada geese (Branta canadensis maxima) from Toronto, Ont. (43°37′N, 79°20′W), collected during early and late egg laying in 1980 and 1981, and during incubation and moult in 1981. Early nesting geese had more fat, though not more protein, than late nesting birds in both years. Geese collected in 1981 had more fat and protein than geese collected in 1980. Early and late laying females in both years lost on average 198 g (26%) of fat and 34 g (5%) of protein from the beginning to the end of laying. Fifty-eight percent of the fat reserves possessed at the beginning of laying were lost during incubation. Fat reserves of prelaying Branta canadensis interior nesting on the James Bay lowland (53°15′N, 82°09′W) in 1980 were 9% greater than those of B. c. maxima nesting in Southern Ontario. During the moult at Toronto, Canada geese lost weight from flight muscles while gaining weight in other muscles and in fat. This pattern is seen in waterfowl moulting at several latitudes, and indicates that geese moulting in both southern and northern latitudes probably rely on nutrients in food rather than in body tissues to supply growing feathers.