Molt chronology of male Mallards wintering in Missouri

摘要

Patterns of molt vary among groups and species of waterfowl (Family Anatidae). Geese, swans, and whistling ducks have a single annual molt, generally initiated during summer; most other waterfowl have two body molts, one (the prealternate molt) initiated during summer or fall and the other (the prebasic molt) initiated at various times of the year, dependent upon species and sex specific strategies (Hohman et al. 1992). Additional molts (supplemental molts) have been reported for the Oldsquaw (Clangula hyemalis) (Salomonsen 1941) and may exist in other waterfowl species. Molt chronology has been examined for a number of waterfowl species, and several factors have been shown to influence the timing of molt. Species specific differences exist even among closely related species (e.g., dabbling ducks of the tribe Anatini) and are directly related to pairing strategies; males of species that form pair bonds early in the fall or winter complete the prealternate molt earlier than those that pair later (Hohman et al. 1992). Sexual differences in molt chronology of dabbling ducks are related to role differences in the reproductive cycle. Females undergo a prolonged prebasic molt during spring and early summer to provide additional concealment during nesting, whereas males complete a short prebasic molt during mid-summer and retain their alternate plumage for a longer period (Palmer 1972). Most male dabbling ducks do not pair until the alternate plumage is in an advanced stage of development (Klint 1980; Wishart 1983; Paulus 1984; Hohman and An-kney, in press), and young males often complete the prealternate molt later than adults (Wishart 1983, Hohman et al. 1992).