Ecology of breeding mallards : nest parasitism; brood survival; and habitat utilization

Graduation date: 1980In 1976 and 1977 I examined three broad problems associated with the recruitment of young mallards, Anas platyrhynchos, in the Prairie Pothole Region of North Dakota. The three problems studied were: the effects of interspecific nest parasitism on production; the chronology and magnitude of total-brood loss during the brood-rearing period; and, mobility, home range, and habitat utilization of broods. Nest parasitism occurred only in mallard nests that were in marsh habitat. Of 24 active mallard nests located in marsh habitat during 1976, 46% were parasitized. Forty-two percent were parasitized by redheads, Aythya americana, and 8% by ruddy ducks, Oxyura jamaicensis. Only three mallard nests were found in marsh habitat in 1977, presumably because of a severe drought, and none were parasitized. Nest parasitism by redheads or ruddy ducks did not significantly decrease mallard nest success (P>0.05). Parasitism by redheads reduced mallard clutch-size by about 1.5 eggs; parasitism by ruddy ducks had no significant effect on mallard clutch-size. In successful nests, nest parasitism by redheads significantly reduced mallard egg success (P