1. Alaska Science Center; U.S. Geological Survey; 4210 University Drive Anchorage AK 99508 USA
2. Department of Coastal Systems; NIOZ Royal Netherlands Institute for Sea Research; Utrecht University; PO Box 59, 1790 AB Den Burg Texel The Netherlands
3. Chair in Global Flyway Ecology, Conservation Ecology Group; Groningen Institute for Evolutionary Life Sciences (GELIFES); University of Groningen; PO Box 11103 9700 CC Groningen The Netherlands