Census methodologies of Black-legged Kittiwakes in Glacier Bay National Park

Black-legged Kittiwakes (Rissa tridactyla) have recently experienced widespread population declines and frequent colony failures throughout the North Pacific. At Glacier Bay National Park, the Margerie Glacier colony was censused visually in 1991 through 1993. In 1993 a new photographic census technique was also tested to assess its feasibility, accuracy, and ease of use, Three years of monitoring data indicate that kittiwake population size declined by about 10% over the three-year period, and that there were near-total colony reproductive failures in 1991 and 1992. Compared to visual colony counts made from a skiff, counting adult kittiwakes from projected 35-mm slides proved to be both more efficient and equally accurate.