Annual migrations of shorebirds are among the longest treks in the world. Whimbrels are among the most far-reaching, with movements between subarctic and Arctic breeding grounds to non-breeding locations in the southern hemisphere spanning up to 5,400 miles.
Not a simple point A to point B calculation, these annual trips vary in timing, site selection and more. Understanding variation in these traits among populations can help uncover mechanisms driving migratory behaviors and identify potential population threats.
In a study published this month in the Journal of Field Ornithology, ACR Director of Conservation Science Nils Warnock and co-authors set out to discover the nuances in movements of Whimbrels breeding in Alaska, a population that numbers nearly 40,000 during breeding season. Between 2009–10, we satellite-tagged a total of 31 Whimbrels at two breeding areas— Kanuti National Wildlife Refuge, an interior boreal forest site roughly 250 miles from the coast, and at a tundra site on the North Slope of Alaska, roughly 20 miles from the Arctic Ocean—then tracked the birds through 2015.
Our top takeaways from this study:
• The tagged Whimbrels moved entirely within the Pacific Americas Flyway—some making nonstop flights that exceeded 7 days across nearly 5,400 miles—and spent their non-breeding seasons at coastal sites extending from the Sea of Cortez, Mexico to Chiloé Island, Chile (a whopping 70-degree range of latitude).
• The Alaska-breeding Whimbrels exhibited greater variation in migratory behaviors than those in other populations (e.g. in Europe and Asia) in the species’ range, beginning earlier and ending later, depending on distances being migrated.
• Individual Whimbrels were highly faithful to favorite breeding and non-breeding sites. While we saw a preference for undisturbed coastal habitats during non-breeding periods (these sites may offer additional benefits, such as decreased predation risk and reduced disturbance), they were less risk-adverse about stop-over sites, often choosing human-modified environments, like agricultural lands in the Central and Imperial valleys of California, that may provide abundant, high-energy food resources during migration.
Understanding movement patterns, timing, site selection and preferences of migratory birds helps focus conservation efforts on the areas most important to them. In the case of Pacific Flyway Whimbrels, they showed high fidelity to a number of breeding, wintering, and stopover sites among years. For site faithful birds, like Whimbrel, loss of particular sites and habitats may have especially negative consequences.
photo: Len Blumin / Gordon Sherman Photo Library