Marsden S.J. & Sullivan M.S. (2000) Intersexual differences in feeding ecology in a male dominated wintering Pochard Aythya ferina population. ARDEA 88 (1): 1-7

Intersexual differences in feeding rates, aggression rates, and feeding site selection were investigated in a flock of up to 2700 Pochard Aythya ferina wintering at Salford docks, Greater Manchester (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 little 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 densities. There was, however, a strong positive relationship between the proportion of males in feeding groups and distance to the shoreline in three directions. We suggest that differences in habitat preference between the sexes of wintering diving duck may be more important in determining local distribution of sexes than is aggression through male dominance