Using Satellite and Radio Telemetry to Examine Stopover and Migration Ecology of the Whimbrel: 2009-2011 Report
The whimbrel (Numenius phaeopus) is a large, Holarctic, highly migratory shorebird. The North American race (N.p. hudsonicus) includes two disjunct breeding populations, both of which winter primarily in Central and South America. The western population breeds in Alaska and the Northwest Territories of Canada (Engelmoer and Roselaar 1998). The eastern population breeds south and west of Hudson Bay in Manitoba and Ontario (Skeel and Mallory 1996, Jehl and Smith 1970). The prevailing idea was that the western population followed a Pacific Coast migration route between breeding and wintering areas in Panama and western South America, and that the Hudson Bay population followed an Atlantic Coast migration route to wintering grounds in Northeast South America (Andres et al. 2009, Skeel and Mallory 1996, Morrison and Ross 1989). Both populations are of high conservation concern due to population declines in recent decades (Bart et al. 2007, Morrison et al. 2006, Watts and Truitt in press). Investigations into the migration routes of whimbrels staging in Virginia have shown a previously unknown link between the eastern and western populations as they stop-over in Virginia (Watts et al. 2008). The primary objective of this project is to examine the stop-over and migration strategies of whimbrels, as they relate to the conservation of the species. A total of 12 9.5 gram PTT satellite transmitters were deployed during the 2009-2010 spring and fall migration seasons. Average weight for the whimbrels with transmitters was 568 ± 53SD grams, or approximately 150-200 grams over mean winter (lean) weight. A total of 67 digitally coded glue-on radio transmitters were attached to birds during these seasons. The cumulative data give us insight into stop-over times for whimbrels as they stage on the Eastern Shore of Virginia before migrating to both breeding and wintering grounds. Satellite and radio transmittered whimbrels departed the Eastern Shore in the spring season between 22 May and 3 June and in the fall season between 11 August and 20 September. Spring birds tend to leave during a short window (CCB/TNC spring whimbrel count unpublished data), whereas fall birds have a much bigger migration window as shown by the wide range of satellite and radio transmitter leave dates. Several unusual migration events were observed during the spring and fall seasons. Twenty flights averaging 2,595 km were documented during the spring seasons. These flights took an average of 81 hours to complete. Twenty-four flights averaging 2,603 km were documented during the fall seasons. These flights took an average of 91hours to complete. A total of 13 shorter flights on breeding grounds were also documented, with birds moving from initial locations in along the Hudson Bay coastline to interior breeding locations. The mean distance traveled on these flights was 435 km with the mean time in flight 44 hours. A total of 17 shorter flights on wintering grounds were documented, with birds moving from initial locations in the Greater and Lesser Antilles, Suriname, and Guyana into French Guiana, Suriname, and Brazil, the primary wintering grounds for the Atlantic population of whimbrels (Morrison and Ross 1989). The mean distance traveled on these flights was 548 km with the mean time in flight 52 hours.