Introduction

This hardy, ornately plumaged duck breeds in remote areas of both the New and the Old World Arctic. Pushed south in fall by advancing sea ice, many winter at the southern extent of the ice, but occasionally immatures venture as far south as Florida and southern California. Adults are among the first birds to return north to breeding areas in spring, even before ice and snow have completely melted. Few birds of any other species nest farther north than the King Eider. There are 2 populations of King Eiders in North America—one that winters in the west, the other in the east. Their migrations are some of the most spectacular passages of birds on the continent. Because of their short arctic breeding season, individuals must arrive early in spring. In coastal northwestern Alaska, flocks of tens of thousands may pass northward during spring migration, often interspersed with other waterfowl and seabirds; such passages can last uninterrupted for hours. Molt and fall migrations can also be impressive, but they are extended over summer and fall.

Because of the remote habitats of the King Eider, information on this species is based on relatively few studies and anecdotal observations. For major nesting areas on Banks and Victoria Is., systematic aerial surveys of King Eider populations were made for the first time in the early 1990s (Dickson et al. 1997). Nesting studies have been few and limited, but have documented habitat use, nest success, behavior, and other important aspects of breeding (Lamothe 1973, Kellett and Alisauskas 1997, Cotter et al. 1997, Holcroft-Weerstra and Dickson 1997). Detailed behavioral and feeding studies have been carried out at molting areas in western Greenland (Frimer 1993, 1994a, 1994b, 1995a, 1995b, 1997). Information on mass mortality events due to adverse weather, and their potential impacts on population dynamics, is available (see Barry 1968, Fournier and Hines 1994). Migration studies (Woodby and Divoky 1982, Suydam et al. 1997) have estimated numbers at Point Barrow, Alaska. Population declines have been sketched for both western and eastern Arctic populations (Mosbech and Boertmann 1999, Suydam et al. 2000). Given such potential declines, additional information is needed on distribution, abundance, survival, reproductive success, and habitat use.