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

Intersexual differences in feeding rates, aggression rates, and feeding sit e selection were investigated in a flock of up to 2700 Pochard Aythya ferin a 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, recor ded levels of aggression had little influence on diving rates, and female d iving rates were unrelated to the number of males present. Males did not te nd to occupy the feeding areas with highest invertebrate densities. There w as, however, a strong positive relationship between the proportion of males in feeding groups and distance to the shoreline in three directions. We su ggest that differences in habitat preference between the sexes of wintering diving duck may be more important in determining local distribution of sex es than is aggression through male dominance.