Status and Trends of Loon Populations Summering in Alaska, 1971-1993

Abstract

Loons (Gavia spp.) were counted during the Alaska-Yukon Waterfowl Breeding Population Survey from 1971 to 1993 and the Arctic Coastal Plain Waterbird Breeding Population Survey from 1986 to 1993. Population indices for Alaska (not corrected for visibility bias) are presented by species for boreal forest, tundra, and both habitats combined. Minimum mean population estimates (1977-1993) with 95% confidence intervals were 15,360 (±2,235) Red-throated Loons (G. stellata), 69,498 (±5,596) Pacific Loons (G. pacifica), 8,886 (±843) Common Loons (G. immer) and 2,636 (±614) Yellow-billed Loons (G. adamsii). Populations of Pacific, Common and Yellow-billed Loons did not change significantly between 1977 and 1993, whereas Red-throated Loons declined by 53% to a 1993 level of 9,843 (±2,447) (r 2 = 0.65, P < 0.001). Factors affecting results from aerial surveys are discussed.