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Ecology of Yellow-billed, Pacific, and Red-throated Loons on the Colville River Delta, Northern Alaska
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 The conservation of loons in Alaska has gained attention due to local declines in some species, small population sizes in others, potential vulnerability to oil and gas development, relatively limited data on which to base predictions, and the general interest of the public in this highly visible and symbolic taxon. The Colville River Delta, in northern Alaska on the coast of the Beaufort Sea, is a relatively rich environment for breeding loons due to its abundance of large deep lakes, intermediate-sized wetlands and polygonal pond fields, and proximity to food-rich waters of the Colville River and Beaufort Sea. With the recent opening of the Alpine Oil Field on the Colville River Delta and impending oil development of the National Petroleum Reserve, the potential for human impacts on loon species has greatly increased. Three species of loons, the yellow-billed (Gavia adamsii), red-throated (Gavia stellata), and Pacific (Gavia pacifica), breed on the Colville River Delta and across the Arctic Coastal Plain. They differ in habitat preferences, specifically the waterbody size on which they rear young, and the extent to which they depend on the brood-rearing waterbody when feeding chicks. The objectives of this study are as follows: 1) Identify high quality habitats by comparing loon abundance and nesting success among habitats. 2) Identify and quantify the importance of factors affecting nesting and brood-rearing success (e.g., fish availability, parental feeding rate, and waterbody size and depth). 3) Quantify annual variability in productivity and the components of productivity (proportion of pairs nesting, clutch size, survival during incubation, and survival during brood-rearing), and identify parameters (e.g., timing of spring, other weather parameters, habitat type) that explain variation in annual productivity in each species. Results
Preliminary estimates of nesting and brood-rearing success have been based on an average of 53 red-throated, 63 Pacific, and 11 yellow-billed loon nests or broods in each of 5 years (1996-2000). Results indicate that productivity varies greatly among years and is related, in part, to the timing of spring ice melt. Yellow-billed loons showed the most variation in productivity. Fish availability has been estimated in 74 brood-rearing waterbodies (all loon species combined), and we have gathered 24 hours of time-budget data on each of 15 red-throated, 24 Pacific, and 10 yellow-billed loon broods.
This project is funded, in part, by the U.S. Fish and Wildlife Service, Region 7, Office of Migratory Birds, Nongame Bird Program, Anchorage, Alaska
Susan Earnst
Address: USGS Snake River Field Station
Address: 970 Lusk Street
Address: Boise, ID 83706
Phone: 208-426-5209
E-mail: susan_earnst@usgs.gov
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