SURVIVAL AND NEST SUCCESS OF SYMPATRIC FEMALE MALLARDS, ANAS-PLATYRHYNCHOS, AND AMERICAN BLACK DUCKS, A-RUBRIPES, BREEDING IN A FORESTED ENVIRONMENT

Inverse population trends of Mallards (Anas platyrhynchos) and America n Black Ducks (A. rubripes) in eastern Canada and northeastern United States have led many to speculate whether differential productivity an d survival exist between these closely related forms. Monitoring of ra dio-marked female Mallards and Black Ducks breeding sympatrically in t he western Adirondack region of northern New York in 1990-1991 showed that nest success rates of Mallards (S = 0.51) and Black Ducks (S = 0. 61) were similar (P > 0.10), as was the survival rates of females duri ng the 107-day breeding period (5 April - 20 July; Mallard S = 0.88. B lack Duck S = 0.77). Despite these similarities, a higher proportion o f Mallards successfully hatched a clutch than did Black Ducks (67% vs. 44%). Thus. Mallards may be more productive than Black Ducks, contrib uting to their increasing numbers throughout Black Duck breeding range .