Geographic variation in morphometrics, molt, and migration suggests ongoing subspeciation in Pacific Golden-Plovers (Pluvialis fulva)

Breeding Pacific Golden-Plovers (Pluvialis fulva) cover 140 longitudinal degrees of Arctic tundra. Having examined 557 museum skins from across this huge distributional range, we conclude that Pacific Golden-Plovers breeding in Alaska are structurally larger than those breeding in Siberia, especially in wing length. Birds from Alaska also have more pointed wings and almost always postpone the initiation of primary molt until they reach their winter quarters, whereas many Siberian birds start primary molt in the breeding areas. These differences could have been favored by the longer transoceanic flights followed by the Alaskan populations to nonbreeding destinations in the Pacific Islands. We propose that the Alaskan and Siberian breeding birds be distinguished as distinct flyway populations to be used in conservation assessments by the international conservation community.