LAUSR

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 = 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 = 2–47) in 2012 and 20 days (range = 1–61) in 2013 to migrate from wintering grounds to summer areas, whereas the duration of fall migration averaged 47 days (range = 7–115). Eiders exhibited high site fidelity to wintering areas, with 83% of birds with active transmitters (n = 23) returning to the study area the following winter (2012–2013). Mean individual core use home ranges on wintering grounds averaged 38.5 km2 and 95% utilization distributions were 199.3 km2. 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-km2 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. © 2017 The Wildlife Society.