Densities of breeding American black ducks in southcentral Maine: 1958-60 and 1978-80

Numbers of wetlands and amount of surface water (ha) within a 105 km2 area increased substantially between 1958-60 and 1978-80 in southcentral Maine. Conversely, in 1978-80 mean numbers of black duck pairs (11.9/100 ha surface water) and broods (10.8/100 ha surface water) were lower than for 1958-60 (pairs = 23.3; broods = 13.3) for wetlands surveyed in both periods. Differences in pairs are discussed in terms of wetland changes and in terms of differences in numbers of black ducks counted in the Atlantic Flyway mid-winter inventory for comparable years.