The breeding behavior of a crowded population of mallards

Abstract

The breeding behavior of a population slightly in excess of 200 free-winged mallard ducks was observed during the breeding seasons of 1966 and 1967. These ducks frequented a 3.1-ha area at the Delta Waterfowl Research Station in Manitoba. The most notable behavioral abnormalities observed in this dense population were a great deal of strife, including fighting among males and females, and rape of females; a high frequency of nest parasitism; abandonment of nests; reduced broodiness of females; loss and abandonment of young; formation of large broods of mixed origin; and, renesting of hens already having produced a brood. Although egg production was high, productivity was low due to a small hatch and to high mortality of young less than 2 weeks old. Aggressive behavior and rape within this population appeared to be responsible for mortality and reduced breeding success.