Research Article Habitat Use and Movements of Common Eiders Wintering in Southern New England JOSHUA M. BEUTH, 1 Department of Natural Resources Science, University of Rhode Island, Kingston, Rhode Island 02881, USA SCOTT R. MCWILLIAMS, Department of Natural Resources Science, University of Rhode Island, Kingston, Rhode Island 02881, USA PETER W.C. PATON, Department of Natural Resources Science, University of Rhode Island, Kingston, Rhode Island 02881, USA JASON E. OSENKOWSKI, Rhode Island Department of Environmental Management, Division of Fish and Wildlife, West Kingston, Rhode Island 02892, USA ABSTRACT Little is known about the habitat use patterns and movement ecology of American common eiders (Somateria mollissima dresseri) despite potential negative impacts on habitat and eider populations from anthropogenic sources (e.g., oil spills, hunting, offshore wind energy facilities). We used satellite telemetry to quantify migratory phenology, home range size, winter site fidelity, and resource selection of adult female eiders (n ¼ 24) from December 2011 to July 2013 that were captured during winter in southern New England, USA. Eiders spent 39% of their annual cycle in southern New England. In spring, eiders took an average of 16 days (range ¼ 2–47) in 2012 and 20 days (range ¼ 1–61) in 2013 to migrate from wintering grounds to summer areas, whereas the duration of fall migration averaged 47 days (range ¼ 7–115). Eiders exhibited high site fidelity to wintering areas, with 83% of birds with active transmitters (n ¼ 23) returning to the study area the following winter (2012–2013). Mean individual core use home ranges on wintering grounds averaged 38.5 km 2 and 95% utilization distributions were 199.3 km 2 . Based on habitat selection models, eiders preferred shallow, nearshore waters that had relatively fine sediments and a high probability of hard bottom. We estimated that only 3% of our 6,212-km 2 study area had a high relative probability of use by eiders. Future development (e.g., offshore wind energy developments) should avoid shallow, nearshore waters with hard bottoms preferred by eiders to minimize potential impacts. Ó 2017 The Wildlife Society. KEY WORDS common eider, migration phenology, satellite telemetry, site fidelity, Somateria mollissima dresseri, southern New England, winter habitat use. Knowledge of habitat use patterns and movement dynamics of sea ducks of North America is limited; most information about their winter ecology is from studies on the Pacific Coast (Bowman et al. 2015, Savard et al. 2015). In southern New England, USA, the American common eider (Somateria mollissima dresserri) is 1 of 5 sea duck species identified as high-priority for study because of population declines or concerns about harvest or habitat limitations (Sea Duck Joint Venture 2014). In addition, eider populations face potential impacts from a variety of anthropogenic and natural sources including offshore wind energy developments (Langston 2013), aquaculture practices (  Zydelis et al. 2006), oil spills (Michel et al. 1998), hunting (Gilliland et al. 2009), and disease (Allison et al. 2015). Numerous offshore wind energy developments are in various stages of development along the northwest Atlantic Coast, including the first active offshore wind energy development in North America: a 5-turbine 30- megawatt (MW) facility off Block Island, Rhode Island, USA that was operational by fall 2016 (Bureau of Ocean Energy Management 2012). Research from existing offshore wind energy developments in Europe suggests sea ducks are vulnerable to displacement from foraging habitats (Bradbury et al. 2014), although such displacement may diminish over time (Petersen and Fox 2007). Further, oil spills in winter have had negative impacts on sea duck populations in the region (Michel et al. 1998); thus, understanding spatiotem- poral dynamics of eiders in southern New England is important to recognize the potential impacts of future spills. Finally, thousands of common eider were killed on 12 occasions from 1998 to 2013 by a novel orthomyxovirus (i.e., Wellfleet Bay virus) near Cape Cod, Massachusetts, USA, and knowledge of eider movements could inform disease transmission models (Allison et al. 2015). The common eider is one of the most abundant sea ducks during winter in northeastern North America (Silverman et al. 2013, Bowman et al. 2015), with 3 recognized subspecies: northern common eider (S. m. borealis), Hudson Bay common eider (S. m. sedentaria), and American common eider (Goudie et al. 2000). American common eiders demonstrate site fidelity to their wintering areas from Newfoundland, Canada to Rhode Island, USA (Merkel et al. 2006, Bowman et al. 2015). Received: 6 August 2015; Accepted: 3 October 2016 1 E-mail: joshua.beuth@dem.ri.gov The Journal of Wildlife Management; DOI: 10.1002/jwmg.21289 Beuth et al.  Common Eiders in New England 1