Intersexual differences in feeding ecology in a male dominated wintering Pochard Aythya ferina population.

Intersexual differences in feeding rates, aggression rates, an d feeding site selection were investi gated in a flock of up to 2700 Pochard Aythya ferina wintering at Salford docks, Greater M anchester (239 males per 100 females) . As often found elsewhere, females were less aggressive than males, males attacked other males less, and females more, than expected. However, recorded levels of aggression had li ttle influence on diving rates, and female diving rates were unrelated to the number of males present . Males did not tend to occupy the feeding areas with highest invertebrate densi ti es . There was, however, a strong posi tive relationship between the proportion of males in feeding groups and dist ance to the shoreline in three direc tions. We suggest that differences in habitat preference between the sexes of wintering diving duck may be more important in determinin g local distributi on of sexes than is aggression through male dominance.

Marsden S .J . & M .S . Sulliv an 2000, Ardea 88(1) : 1-7