Factors affecting reproductive performance in captive Mallard ducks

Propagation of wild-strain Mallards (Anas platyrhynchos) in captivity is hi ndered by low egg fertility. Therefore, we studied the effects of captivity , age, mate choice and isolation on reproductive parameters of Mallards. Ca ptive drakes had smaller immature testes than free-flying Mallard drakes. C aptive yearling ducks weighed less than adult ducks at the beginning of the breeding season, but no differences were found between their initial clutc h size, egg volume or number of clutches laid. Yearling pairs had lower egg fertility (7%) than adult pairs (80%). Egg fertility was higher(51 vs 21%) in self-chosen pairs than in randomly assigned pairs. Isolation of ducks, however did not influence egg production. (C) 1999 by Elsevier Science Inc.