Body Composition of Female Mallards in Winter in Relation to Annual Cycle Events

Abstract

Body mass and carcass composition were determined from 267 female Mallards (Anasplatyrhynchos) collected during the winters of 1980-1981, 1981-1982, and 19821983 in the Mingo Basin of southeastern Missouri. Changes in carcass composition were related to annual events, such as migration, molt, and pairing. Body and carcass masses were similar between adults and immatures within status groups. The first females arriving in the Mingo Basin in fall were mostly adults engaged in the prealternate molt; body (1,010 g) and lipid (65 g) masses of these females in mid-prealternate molt were low compared to females collected at other times during winter. Females gained body and lipid mass following the completion of the prealternate molt and most became paired in November and December. Paired females had greater lipid masses than unpaired females throughout fall and winter. Body and carcass masses of nonmolting females remained constant over winter. Females initiated the prebasic molt with relatively large body (1,118 g) and lipid (168 g) masses. Lipid mass declined curvilinearly through the middle of the prebasic molt but then increased to 188 g and 219 g by late prebasic molt and premigratory stages, respectively. Adults proceeded through annual events earlier than immatures and both immatures and adults proceeded through annual events earlier in the wet winter of 1982-1983 than in the drier winters of 1980-1981 and 1981-1982. Mallards complete annual events earlier than most other ducks and female Mallards that complete annual events early in winter may have, at least historically, realized survival and reproductive potential advantages, especially following wet winters.