Spatial distribution, habitat characteristics and nest-site selection by Tundra Swans on the Central Arctic Coastal Plain, northern Alaska

Annual aerial surveys of nesting Tundra Swans (Cygnus columbianus columbianus) were conducted during 1989-2000 on the Kuparuk and Milne Point oilfields and adjacent areas of the central Arctic Coastal Plain of northern Alaska. Spatial analysis indicated that swans selected nest sites close (less than or equal to100 m) to large lakes (20-33 ha) and that nests were clumped in distribution each year, although nests on average were greater than 2.5 km apart. The clumped distribution of nests suggests that suitable habitats for nesting swans are not randomly distributed in the study area. Mean distance of nests to the Beaufort Sea coastline ranged annually from 11.1-14.5 km. Waterbodies near nests had significantly higher shoreline complexity each year than the closest waterbodies to random locations. Complex shorelines (i.e., small coves or sheltered areas) provide areas suitable for emergent vegetation such as Pendant Grass (Arctophila fulva), a dominant species in preferred foraging habitat in northern Alaska. Photographs of Tundra Swan nests, taken over a seven-year period, were used to characterize nest-site habitats at both macrotype and microtype scales. Nests primarily were located on the driest microtypes and on macrosites associated with lakes, usually within 20 m of the lake shore. Nest sites afforded good visibility and early exposure during spring thaw. Among the 89 swan territories that had at least three years of use, swans used the same mound each year in 36% of territories and used a different mound each year in 12%; swans in remaining territories used the same mound in some years and new mounds in others. Studies such as cuts may be useful for evaluating the impacts of oil development, and for planning and permitting future developments in new regions on the Arctic Coastal Plain of Alaska.