Connecting the Spots - Influences on Site Use by Migratory Pacific Flyway Shorebirds

From Pubwiki

[edit] Author(s)

• Warnock, N.
• Bishop, M. A.
• Takekawa, J.
• Williams, T. D.

[edit] Journal

Journal of Ornithology 147.5, Suppl. 1 (2006): 53-53.

[edit] Meeting Abstract

Over the past 14 years, the Pacific Flyway Shorebird Migration Program has used radio telemetry to trace a clear picture of how Western Sandpipers (Calidris mauri) and other shorebirds (Dunlin, C. alpina, Long- and Short-billed Dowitchers Limnodromus scolopaceus, L. griseus) migrate from Mexico north to their breeding grounds in Alaska. During this period we tracked over 400 birds, many over distances spanning much of their spring migration route. Here we report on results from these studies, including one to be completed in the spring of 2006. We have found that, while individual birds can travel over 3,000 km in a single flight, the majority use a system of stopover sites within hundreds of kilometers of one another. Use of these sites is influenced by sex, date, origin of migration, and age. In 2004, we measured triglyceride levels in migrating Western Sandpipers from Mexico to Alaska as an index of fattening rate. We were able to show, first, that plasma triglyceride levels increased between winter and migration at San Francisco Bay. Secondly, we found that there was a near-linear increase in plasma triglyceride levels with increasing latitude through the spring migration period, from low levels in Mexico to progressively higher levels northwards to the Copper River Delta in Alaska. This suggests that birds fatten progressively as they move north and approach breeding grounds. At San Francisco Bay, length of stay of Western Sandpipers was negatively related to triglyceride levels (P<0.10). Differences among species in the use of stopover sites will also be discussed.