New insight concerning transoceanic migratory pathways of Pacific Golden-Plovers (Pluvialis fulva): The Japan stopover and other linkages as revealed by geolocators

摘要

We used light level archival geolocators (data loggers) to track annual migrations of Pacific Golden-Plovers Pluvialis fulva at non-breeding grounds on American Samoa and Saipan, and at nesting grounds near Nome in W Alaska. Among wintering birds, we deployed loggers in spring 2010 and recovered them during the 2010-2011 nonbreeding season when the site-faithful birds had returned; deployment on breeding birds was in summer 2009 and 2010, logger recovery in each group was one year later when the plovers were again nesting. Logger archives from American Samoa and Nome birds revealed a clockwise, circular transoceanic pattern (previously unknown in this species) consisting of three lengthy movements: 1. southward from Alaska in autumn via the mid-Pacific Flyway (American Samoa birds wintered at the same sites where they had been captured, Nome birds wintered variously at Christmas Island, Marshall Islands, Gilbert Islands, Fiji, and Fraser Is., Queensland); 2. in spring, the plovers traveled north-westward to Japan (the track from Fraser Is. was via Taiwan) where they made stopovers averaging about three weeks; 3. from Japan and Taiwan, the final segment was north-eastward to nesting grounds in Alaska. Great circle distances along this annual clockwise journey varied with location of wintering grounds ranging from about 16,000 to 26,700 km. Flights on each of the three segments appeared to be mostly nonstop at estimated mean ground speeds of 59-78 kph over periods of about 3-8 days. Three individuals made transoceanic passages at apparent record-setting ground speeds in excess of 100 kph. In spring, the Saipan birds followed the East Asian-Australasian Flyway with stopovers in Japan and elsewhere in Asia before arriving at nest sites in Chukotka and Kamchatka. Two Saipan birds made long over-water flights from Japan to W Alaska. One of them traveled from the Seward Peninsula to Chukotka and nested there. Where the other bird nested is uncertain because its geolocator failed. In fall, the individual that had reached Chukotka via Alaska backtracked and made a flight from Alaska across the western Pacific to Saipan. The other Saipan birds returned via mainland Asia and Japan. Our findings indicate that Japan is a key stopover (especially in spring when plovers from widely separated areas of the winter range converge there), and demonstrate that Alaska hosts a breeding population of Pacific Golden-Plovers comprised of birds from most if not all of the Pacific winter range.