Incubation weight loss in the mallard

Abstract

Incubating mallard (Anas platyrhynchos) hens were trapped on their nests in southern Manitoba during 1975–1977 to document weight trends. In 1975, hens lost an average of 7.4 g per day incubating, 18% of the calculated initial body weight. Weight lost during incubation was greatest (27%) for early nesting hens and lowest in late nesting hens (11%). Weight loss patterns were less clear but changes were lower in magnitude in 1976. Possible explanations relating to weather and local population changes are discussed. Recapture weights of individual hens support the relationship between incubation weight loss and nesting chronology.