POPULATION TRENDS OF BLACK TERNS FROM THE NORTH-AMERICAN-BREEDING-BIRD-SURVEY, 1966-1996

Data from the North American Breeding Bird Survey indicate a survey-wi de decline in Black Terns (Chlidonias niger) at an average rate of 3.1 % annually during 1966-1996. Black Terns in Canada decreased at an ave rage annual rate of 3.5% during this interval, while the United States population showed no significant trends. These long-term declines lar gely reflect trends prior to 1980, when the continental, Canadian, and United States populations decreased at average annual rates of 7.5%, 5.6%, and 11.9%, respectively. Most population trends were reversed du ring the 1990s, causing trend estimates over the 1980-1996 interval to become more positive. Associations between patterns of change in Blac k Terns, Mallards (Anas platyrhynchos), and numbers of ponds in the no rthern Great plains suggest some relationships exist between habitat a vailability and the population trajectories.