Long-tailed ducks © Dave Larson, Mass Audubon

In late 2001, the Cape Wind energy project was proposed for Horseshoe Shoal in Nantucket Sound, and a comprehensive environmental review process began almost immediately. Nantucket Sound is the winter home for large numbers of sea ducks, particularly long-tailed duck (Clangula hyemalis), all three North American scoters, and common eider.

Long-tailed duck is listed as vulnerable to global extinction by the International Union for the Conservation of Nature, and relies heavily on Massachusetts’ coast for its overwintering habitat. Therefore, during the scoping phase of this project, Mass Audubon and others recommended that the environmental review include comprehensive surveys of avian use of the Sound. 

Hundreds of thousands of long-tailed ducks exit the Nantucket Sound each day at dawn, commute to feeding sites on Nantucket Shoals, and return to roosting sites in the Sound at dusk. Prior to our research, however,  the locations of these roost sites were unknown.

Our primary goal was to identify whether or not Horseshoe Shoal was used by large numbers of long-tailed ducks as a nighttime roosting site, or as a staging area as they exit or return to the Sound. If the answer to either of these questions is yes, then long-tailed ducks are potentially at risk of collision with wind turbines as they enter, exit, or otherwise move within the project area. We also obtained information about links between Massachusetts overwintering populations and breeding areas in northern Canada, which are currently not well understood.