Great Cormorant

Although most people are somewhat familiar with the image of a black cormorant perched with its wings spread on a rock or pier, relatively few know that two different species can be found in New Hampshire. The more common Double-crested Cormorant occurs during the warmer months (and breeds at the Isles of Shoals), but is replaced in winter by its larger northern relative. Great Cormorants breed no closer than mid-coast Maine, and even these are a somewhat recent colonist (1980s) from Atlantic Canada.

Great Cormorants might even be a “recent” (glacially-speaking) colonist to North America, although detailed historical data are lacking. This has been proposed because the coastal birds we have on this side of the Atlantic are the same subspecies as those that occur in northwestern Europe and may have crossed over at some point since the last ice age. The species is far more widespread in the Eastern Hemisphere, where it can be found in freshwater and coastal habitats across much of Eurasia, parts of Southern Africa, and eastern Australia.

Separating Great from Double-crested Cormorants requires consideration of habitat, season, and field marks. As the name implies, the Great is larger and bulkier, but this is often only obvious via direct comparison. Greats also have yellow (vs. orange) throat skin, and this is bordered by white in adults. Immature birds are brown with paler bellies, while young Double-crests are pale on the neck and breast. Some of the best clues relate to where and when you see a cormorant. Great Cormorants are almost exclusively coastal (a few wander up large rivers on occasion) and rarely seen from May through September. Double-crests use both salt and fresh water but are rare in winter. The two overlap in fall and early spring, which is when you can put the field marks to best use.