The Great Black-backed Gull breeds along the east coast of North America from Labrador to North Carolina (Good 1998). This species winters throughout much of its breeding range south along the Atlantic Coast to central Florida as well as the Great Lakes region (Sibley 2014). In Montana, the Great Black-backed Gull has no records over the past decade although historic records exist for this species (Montana Bird Distribution Committee 2012).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.