The Common Loon (Gavia immer) is often used as an indicator species for a variety of environmental contaminants and impacts. Prior research has focused on summer breeding grounds and the threats loons face there. Little is known about winter habitat use and behavior beyond the birds’ movement from fresh-water inland lakes to coastal bays and estuaries following lake freezing. Data from previous studies of wintering habitat are contradictory and focus on particular behaviors with only limited attention to threats. This study sought to determine habitat preference of wintering Common Loons and assess potential threats they face in the vicinity of Acadia National Park, Mount Desert Island, Maine. I conducted regular transects of shoreline habitats, observing loons in coves, inlets, and other areas around the island and mapped their positions into a GIS. I determined the precise location of each loon using surveying compasses and triangulation or a rangefinder, and a Garmin GPS unit. I also recorded weather, sea ice coverage, other species present, and any potential threats or anomalies.
Results/Conclusions
Preliminary results suggest Common Loons show preference for specific coves and that individual loons have some degree of site fidelity. Weather and other bird species do not appear to significantly affect loon behavior or location. Wintering loons do not appear to be good indicators of short term climate change effects because margins of coves and upper bays that freeze seem otherwise unsuitable for habitat, however a decrease in sea ice could lead to significant shifts in habitat use, both providing loons with more wintering areas and exposing them to a new range of threats.