ABSTRACT
Abstract. The value of existing waterfowl survey data for assessing the status and trends of North American sea duck populations is limited due to short time series, insufcient geographic coverage, improper timing, and species identication problems. Despite these shortcomings, contemporary data provide insights into the status of several sea duck populations. In this chapter, we synthesize available information on population status and trends in abundance for sea ducks and recommend efforts that could improve our ability to monitor sea duck populations. The Alaska breeding population of Spectacled Eiders is currently stable (Arctic Coastal Plain) or increasing (Yukon-Kuskokwim Delta) in numbers. Steller’s Eiders (Polysticta stelleri) wintering in Alaska have declined since the early 1990s. Spectacled and Steller’s Eiders remain below historic levels and are listed as threatened in the United States. In western North America, King Eiders (Somateria spectabilis) declined substantially between the mid1970s and mid-1990s; recent data suggest regional differences, but a stable population overall. There is insufcient information on trend for King Eiders in eastern North America. An assessment of trends for Pacic Common Eiders (S. mollissima
v-nigra) is based on limited information, but data suggest that this subspecies declined substantially in northern parts of its range in the 1980s to the early 2000s. Recent regional trend estimates note declines in central arctic Canada and northwestern Alaska, and stable to increasing numbers in other parts of Alaska. Population trends for American Common Eiders (S. dresseri) are variable range-wide, with apparent increases in northern parts of their range and decreases in southern parts. Trends for Hudson Bay (S. m. sedentaria) and Northern subspecies (S. m. borealis) of Common Eiders are uncertain. The population trajectories of the three scoter species (Melanitta spp.) are also not well understood, but available data suggest that, as a group, scoters decreased from the 1980s to the early 2000s, with greater declines noted in the northern boreal forest and northern prairies than in Alaska, and with overall increases since about 2004. Black Scoters on Pacic breeding areas have declined signicantly since the mid1970s, but have increased in number in the last decade. There is no measurable trend for eastern Black Scoters. The limited data for Long-tailed Ducks (Clangula hyemalis) suggest long-term declines in the parts of their range that are surveyed, with
more stable numbers in recent years. Bufeheads (Bucephala albeola), goldeneyes (B. clangula and B. islandica) and mergansers (Mergus spp. and Lophodytes cucullatus) have increased, although lack of differentiation among species of both goldeneyes and mergansers prohibits reliable species-specic evaluations. Numbers of Harlequin Ducks (Histrionicus histrionicus) along the Atlantic coast are increasing, while the Pacic trend is unknown. Data suggest that, for the 22 populations of North America sea ducks currently recognized as distinct or allopatric, 11 populations appear to be stable or have increased in abundance over the last 10-20 years, and two populations are apparently declining. Data are insufcient to determine status for the remaining nine populations. Reliable information
about population status and trends requires surveys designed with specic consideration of sea duck distribution and phenology. We recommend increasing observer training, incorporating detection adjustments, and using aerial photography to improve the accuracy of species identication and abundance estimation. Management agencies in the United States and Canada must devote greater resources to monitoring sea ducks if they wish to better inform harvest management, focus habitat conservation efforts on areas of greatest importance to sea ducks, and effectively evaluate their management actions.
