The sexual behaviour of Muscovy duck (Cairina moschata domestica L.) was compared with the interspecific mating pattern of male Muscovy x female game-farm Mallard (Anas platyrhynchos) and of the reciprocal cross, to see whether behaviour differences may partly account for the low fertility in the interspecific crosses. In this study we also compared the interspecific sexual behaviour of animals which cohabited for a brief or a long period. From the study it appears that there are some evident behavioural differences between these two species that sometimes prevent mating. If ducklings of both species are raised together, a better understanding between the partners seem to be. While a prolonged cohabitation, starting from sexual maturity did not affect the behaviour of mating.