CHANGES IN NUMBERS OF WINTERING AMERICAN BLACK DUCKS AND MALLARDS IN URBAN CAPE BRETON ISLAND, NOVA SCOTIA

Abstract

We studied wintering populations of Mallards (Anas platyrhynchos Linnaeus) and American Black Ducks (A. rubripes Brewster) in urban parks in the industrial area of Cape Breton Island, Nova Scotia during December 1992 and January 1993 and during February and March, 1999–2002. Wintering flocks of Mallards and American Black Ducks have been fed in these parks for more than 30 years. We found that the numbers of American Black Ducks and Mallards have remained relatively stable for the last four years. No evidence exists that the population of Mallards was increasing nor that the population of American Black Ducks was decreasing. Numbers of ducks have fluctuated yearly, but numbers of these species have fluctuated synchronously. We conclude that numbers of American Black Ducks are not declining and are not being replaced by Mallards on Cape Breton Island. Furthermore, no evidence exists of genetic swamping because the proportion of hybrids in the local wintering population did not change.