White-Winged Scoters

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White-winged Scoters Movements and Habitat Use in Southern New England

By Dustin Meattey, University of Rhode Island & Biodiversity Research Institute

Peter Paton

Sea ducks are some of the most prized waterfowl species for duck hunters, wildlife photographers, and birders. The coastal waters and offshore environments in southern New England provide crucial winter habitat for several species including Common Eiders, all three species of scoters (Black, White-winged, Surf), and Long-tailed Ducks. Over the past several decades, population declines of many sea duck species have highlighted the need for a better understanding of their habitat preferences, migration patterns and timing, and linkages between important geographic areas throughout their life cycle. Reasons for these declines remain poorly understood, but habitat conditions and disturbance on the wintering grounds may have carry-over effects impacting annual survival and breeding productivity during subsequent seasons. Because sea ducks spend much of their annual cycle in nonbreeding areas where human-induced threats are often greatest, understanding habitat use on their wintering grounds is crucial for conservation planning. As the development of offshore wind power moves closer to large-scale implementation in the northeastern United States, particularly in areas used by sea ducks during winter, identifying important habitats used by wintering sea ducks informs the planning process and helps avoid displacement of sea ducks from preferred habitats.

Fig. 1. Estimated probability of use by adult female White-winged Scoters in nearshore and offshore waters in southern New England based on movements of satellite-tagged birds.

One species of sea duck that inhabits New England coastal waters during the wintering period is the White-winged Scoter (Melanitta fusca). White-winged Scoters are a long-lived sea duck species that winters along both the Atlantic and Pacific coasts of North America, with increasing numbers also wintering on the Great Lakes. White-winged Scoters nest throughout the interior boreal forest from Alaska to central Canada, with geographically separate eastern and western populations, although some studies have suggested that birds from Atlantic and Pacific coasts may overlap on the breeding grounds. Like most other sea duck species, White-winged Scoters have apparently experienced a long-term population decline throughout the last half-century.

Researchers from RI DEM, University of Rhode Island, Biodiversity Research Institute, and the Canadian Wildlife Service partnered together between 2015 and 2018 to study the movement ecology of White-winged Scoters. We deployed over 50 satellite transmitters in adult females on their wintering grounds in southern New England and at a molting area in the St. Lawrence River Estuary in Quebec. We were able to follow the movements of many individuals for over two years, as they traversed thousands of miles between wintering areas on the East Coast to breeding grounds across the northern boreal forest from Quebec to the Northwest Territories of Canada, on their return migration to important molting and then wintering areas, and for some back again to the breeding grounds.

The data gathered from these birds allowed us to calculate the size and habitat characteristics of winter home ranges, and to identify specific areas in southern New England during winter that were preferred by White-winged Scoters (Fig. 1). Our results suggested that offshore sites predicted to be most used by scoters had very minimal overlap with currently leased and proposed wind energy areas in southern New England. However, many birds made long-distance flights throughout the winter between areas like Montauk Point, NY and the Nantucket Shoals south of Nantucket Island, therefore they were often crossing wind energy areas as they moved between their preferred sites. This suggests that future wind energy development in the currently proposed wind energy lease blocks could pose a deterrent or barrier to these important within-winter movements.

Using the movement data from these scoters, we were also able to identify and document their primary migration routes between breeding and wintering areas and the timing of these movements (Figs. 2, 3). This information is important for biologists responsible for designating hunting seasons and for protecting key areas used during migration, and for others responsible for managing offshore wind farms and other potential sources of disturbance.

Fig. 2. Movements by satellite-tagged adult female White-winged Scoters in spring from wintering sites to breeding locations.

White-winged Scoters wintering in coastal New England bred throughout northern Canada from northern Quebec to the Northwest Territories. After leaving the breeding grounds, scoters underwent a month-long wing molt primarily in James Bay and the St. Lawrence River Estuary before continuing their fall migration back to their primary wintering grounds in southern New England. An important finding from this research was that migration timing was consistent among all birds in our study, regardless of where they bred or molted, and regardless of what route they decided to take. Essentially, the eastern portion of the continental White-winged Scoter population seems to function as a single, continuous population with little evidence of any geographically distinct sub-populations. This suggests that our current harvest of White-winged Scoters would not disproportionately target any particular segment of the population.

Our hope is that this project provides helpful information to policy makers, developers, and biologists to best conserve and manage this important species. This study was part of the Atlantic and Great Lakes Sea Duck Migration Study, a multi-partner collaborative project initiated by the Sea Duck Joint Venture. Funding for this project was provided by the Sea Duck Joint Venture, RI DEM Fish and Wildlife using Federal Aid to Wildlife Restoration funds made available through the Pittman-Robertson Act and the University of Rhode Island. More information can be found at seaduckjv.org.

Fig. 3. Movements by satellite-tagged adult female White-winged Scoters in fall from breeding locations to molting and wintering sites.