The many birds I and other Maine Audubon members saw on our recent trip to Isle au Haut were both a delight and a challenge. This was especially so in the case of the great cormorant seen – or, not seen – by a few of our group.

There are six kinds of cormorants that inhabit certain portions of North America, depending on the season. There are the neotropic, red-faced, pelagic, and Brandt’s cormorants, as well as a cormorant-like bird called the anhinga. Two types of cormorants are found on the Northeast coast or inland: the double-crested cormorant and the great cormorant.

All cormorants have a very distinctive, low-in-the-water profile, and all have black, glossy bodies. Because their feathers are not water-repellant, they spend a lot of their time out of the water on exposed perches, holding their wings out to dry. A large group of them all standing together like this is quite a comical sight.

Differences between the great and double-crested cormorants are easy to see if you see the bird up close, on a calm, bright day with the light just right. But as is the case most of the time, ideal conditions for picking out differences in plumage exist only in the imagination. Once you learn what to look for, details are easy to pick out; but it takes a practiced eye to discern such things, as I was soon to learn.

Never mind that aquatic environments present their own challenges to identifying birds. The day the great cormorant appeared was overcast and windy, creating white-capped swells pockmarked with rain. We had headed down a moss-covered trail to a small cove to see if any harlequin ducks were about; none were, and the Atlantic seemed gloomy and forbidding. But just beyond the breaking waves something large and dark bobbed, then quickly flipped beneath the surface again.

Soon it popped up like a cork, only to be hidden for long seconds by the rushing swells. I was told it was a great cormorant, but the distance and gloom made it impossible for me to tell. So I was determined to study this bird closely so I’d be better equipped to identify it next time around.

The great cormorant is slightly longer in length and twice as heavy as the more common double-crested cormorant. It has a blockier appearance as well – in my mind I compared a Great Dane to a greyhound to remember the difference. It also has a distinctive yellow chin – a golden band extending from its eye underneath the base of its bill. Below this is a broad, white throat.

The double-crested cormorant does not have a white throat, and its chin is more orange than yellow. Its lores – the area of tiny feathers between the eye and bill – are also orange, whereas the great cormorant’s are dark. These features are more obvious in adults, but show up in young birds as well.

Of course, during the breeding season the double-crested cormorant develops the feathery structures it was named for – two plumes on either sides of its head – making identification easier.

But what’s the fun in always making an easy identification?

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com