Presentation Abstract
Long distant migrants timing their arrival on the breeding grounds must make the tradeoff of optimal timing for breeding vs. optimal timing for survival. For many shorebird species, the flyway northward spans thousands of kilometers, and both conditions encountered en route and the priorities of individuals can affect the timing of migration. We used data from spring migration surveys of Western Sandpipers (Calidris mauri) and Pacific Dunlins (Calidris alpina pacifica) along the Pacific Flyway of North America to determine if the timing of their northward movements changed from 1985 to 2016. We examined 5 sites of varying size along the northern portion of the flyway from Washington, British Columbia, and Alaska, and estimated interannual trends in passage timing relative to each site’s distance to the breeding grounds. The peak passage dates at the sites closest to the species’ breeding grounds in Alaska shifted later by 1-2 days over the study period, while date of peak passage at sites further south shifted ~3 days earlier. A post-hoc analysis suggested local temperature also affected passage dates at most sites, with warmer temperatures being related to earlier passage. Discerning patterns of movement by Dunlins at southern sites was complicated by the presence of winter residents. Simulation analyses of sandpiper movement through a stopover site highlighted both length of stay and timing of arrival as important factors shaping peak passage estimates. We suggest Western Sandpipers appear to be arriving earlier at southern sites, and are spending longer at larger stopover sites such as Alaska’s Copper River Delta. Our analysis generates specific predictions for expected behavior on northward migration and we believe may be a useful indicator in other systems where historical count data are available. Key
Session Title
Shorebird Monitoring in the Salish Sea
Keywords
Shore birds, Monitoring, Estuary
Conference Track
SSE7: Monitoring: Species and Habitats
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE7-477
Start Date
4-4-2018 4:15 PM
End Date
4-4-2018 4:30 PM
Type of Presentation
Oral
Genre/Form
presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Calidris--Migration--Northwest, Pacific; Flyways--Northwest, Pacific--Computer simulation
Geographic Coverage
Northwest, Pacific; Salish Sea (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Divergent trends in migration timing of shorebirds along the Pacific flyway
Long distant migrants timing their arrival on the breeding grounds must make the tradeoff of optimal timing for breeding vs. optimal timing for survival. For many shorebird species, the flyway northward spans thousands of kilometers, and both conditions encountered en route and the priorities of individuals can affect the timing of migration. We used data from spring migration surveys of Western Sandpipers (Calidris mauri) and Pacific Dunlins (Calidris alpina pacifica) along the Pacific Flyway of North America to determine if the timing of their northward movements changed from 1985 to 2016. We examined 5 sites of varying size along the northern portion of the flyway from Washington, British Columbia, and Alaska, and estimated interannual trends in passage timing relative to each site’s distance to the breeding grounds. The peak passage dates at the sites closest to the species’ breeding grounds in Alaska shifted later by 1-2 days over the study period, while date of peak passage at sites further south shifted ~3 days earlier. A post-hoc analysis suggested local temperature also affected passage dates at most sites, with warmer temperatures being related to earlier passage. Discerning patterns of movement by Dunlins at southern sites was complicated by the presence of winter residents. Simulation analyses of sandpiper movement through a stopover site highlighted both length of stay and timing of arrival as important factors shaping peak passage estimates. We suggest Western Sandpipers appear to be arriving earlier at southern sites, and are spending longer at larger stopover sites such as Alaska’s Copper River Delta. Our analysis generates specific predictions for expected behavior on northward migration and we believe may be a useful indicator in other systems where historical count data are available. Key
