Factors affecting reproductive performance in captive Mallard ducks

Propagation of wild-strain Mallards (Anas platyrhynchos) in captivity is hindered by low egg fertility. Therefore, we studied the effects of captivity, age, mate choice and isolation on reproductive parameters of Mallards. Captive drakes had smaller immature testes than free-flying Mallard drakes. Captive yearling ducks weighed less than adult ducks at the beginning of the breeding season, but no differences were found between their initial clutch 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.