ID Challenge: Cormorants Unveiled

When I’m in the company of less-experienced birders, I’m often asked, “How can you tell what that is from this far away?” The obnoxious part of my personality wants to quote a friend, who once responded to this question with, “The first ten thousand were a little tougher.” However, I prefer to use occasions such as these to share those clues that aren’t well communicated in most field guides. 

Newer birders tend to focus their attention on the plumage, bill, feet and other aspects of birds that require determinations of color. Unfortunately, birding does not occur in a paradise of ideal lighting and viewing conditions.

As Greg Gillson points out in his response to the Cormorant ID Challenge, some of us are reaching an age where our vision is a bit “compromised.” Living in the Pacific Northwest involves spending half of the year wiping liquid sunshine off one’s optics and recently acquired eyeglasses. In such conditions, discerning minor differences in color, particularly on all-dark birds like cormorants, is challenging at best and often impossible. Thus, learning differences in size, shape, and proportion is critical if you hope to avoid listing “cormorant, sp.” on your Christmas Bird Count tally sheet.

When I came upon this group of cormorants last December, I took time to examine them closely, reconfirming impressions of size and shape that were first learned nearly three decades ago. The photo used in the “Cormorant ID Challenge” was taken with the understanding that the subtle differences in hue would be lost due to low light and dense overcast conditions. In essence, the resulting image is reminiscent of those silhouette drawings that appeared in the early Peterson Field Guides.

Three species of cormorant--Double-crested, Brandt’s, and Pelagic--occur commonly along the Pacific coast of North America. All are likely to be seen flocked together in coastal areas. Only Double-crested is likely to be encountered away from the outer coast. The discussion below will outline the differences in shape and proportion that allow these three species to be separated at a distance. It will also make mention of field marks that may or may not have been of use in identifying the birds in the original image.

Double-crested Cormorant generally appears to be the largest of these three species (Brandt's Cormorants actually weigh more). While their overall length is nearly identical to Brandt’s Cormorant, they look heavier-bodied and have a larger and blockier head. The neck of Double-crested invariably looks thicker, and these birds hold their necks slightly crooked in nearly all postures. This is particularly obvious in flight. Their crowns generally look somewhat flat and there is normally a discernible angle between the hindcrown and the nape. Double-crested Cormorants often show a slightly brownish cast to their plumage, especially during the winter months, while other west coast cormorants look glossy black except when they are juveniles. All Double-crested Cormorants show a sizeable patch of orange or yellow-orange facial skin at the base of the bill. This is called the gular (think jugular) pouch. Their bill is paler (mostly yellow-orange on immatures) than those of the other two species, which have black bills.

In the image presented, bird “E” is the only Double-crested Cormorant. It is clearly looks a bit bulkier, heavier-necked, larger-headed, and holds its neck more crooked than the other birds. Even in the original picture the orange facial skin and lighter bill can be seen.

These two birds (“D” and “E” in the original image) offer a nice comparison of Pelagic (left) and Double-crested (right) cormorants. Note the much smaller size, extremely thin bill, slight crest on the forecrown, and slender head and neck of the Pelagic. Conversely, the Double-crested looks much bulkier and shows a yellow-orange bill, orange facial skin, slightly brownish plumage color, a heavy neck, and a large blocky head.

Now to Brandt’s Cormorant. As stated above, they’re close in length to Double-cresteds, but they are more slender-bodied, and their heads are a bit smaller. Additionally, the necks of Brandt’s are thinner than those of Double-crested. In most postures, Brandt’s hold their necks only slightly crooked, and in flight the neck is almost always fully extended. Both in flight and when perched, it’s possible to see that the head of a Brandt’s presents a “bulbous” look, meaning that it is slightly greater in diameter than the neck. Their bills are slightly less heavy at the base than Double-crested, but often look proportionally longer, which is probably due to the difference in head size. The head shape of a perched Brandt’s is more rounded than the other two species. Brandt’s often appear to have a steeper forehead than the other two species and the crown and nape typically look more rounded. Bird “C” offers a good example of this head profile. In nearly all lighting, the plumage of Brandt’s Cormorants looks jet black. Their bills are entirely dark at every age. Adults in high breeding condition show brilliant blue gular pouches bordered below by a patch of pale tan to cream-colored feathering. When seen well, tw0 long thin white back plumes may be evident. The light colored feathering on the throat is retained throughout the year and is diagnostic for Brandt’s. Looking closely, you can see this light patch on a couple of the birds in the photo (especially if you break the unstated BirdFellow ID Challenge rules by enlarging the photo!). In the original photo, birds “A,” “C,” “G,” and “H” are Brandt’s Cormorants.

This cropped image offers an excellent comparison of the size and shape of Pelagic and Brandt’s Cormorants. The tan throat feathering is apparent on both of the Brandt’s (lower right and top middle birds), while the smaller-billed Pelagics are entirely dark-faced. Note also that the Pelagic on the far left shows a slight crest on the forecrown. This peaked this minor feature contributes to the rather flat-crowned appearance of Pelagics, while the upper Brandt’s shows a characteristic steeper forecrown and rounded hindcrown and nape profile.

Pelagic Cormorants are decidedly smaller and more slender overall than the other two species, and this is typically obvious in mixed flocks. In the referenced image, birds “D,” “F,” and “I” are noticeably smaller than the others. They are smaller in both length and bulk, and they have very slender necks, often described as “snaky.”

Their somewhat flat-crowned heads are also small and slender, typically showing little if any of the bulbous effect exhibited by Brandt’s and Double-crested. In flight the neck and head are always fully extended, and the head will appear to be the same diameter as the neck. When perched, one can often see a noticeable peak or slight crest on the forecrown of a Pelagic. This feature can be seen on both birds “D” and “F.”

The all-dark bill of a Pelagic is shorter and much more slender than those of the other two species. Compared to Brandt’s and Double-crested cormorants, Pelagics have a tiny gular pouch, which is all but invisible most of the year. In alternate plumaged birds, it is possible to see the small dark red pouch in good light. During the winter months their faces and throats look all black.

During the breeding season, adult Pelagic Cormorants also develop gleaming white flank patches at the base of the tail, which are diagnostic for Pelagic when seen. By now you may have noticed that “B” has not been mentioned. This is the wild card of the group. In size, it appears to be as tall, or nearly so, as the Brandt’s (birds “A” and “C”) on each side of it. This is an optical illusion, which illustrates the time-honored axiom that apparent size difference does not always translate to an actual size difference. It is important to use multiple characteristics when identifying birds.

Looking closely at bird “B,” you can see that the neck and head are both thinner and smaller than those of the neighboring Brandt’s Cormorants. Also, the bill is much thinner, and the head is about the same diameter as the neck. Though the lighting is poor, you can see the outline of the pale throat feathering on the two Brandt’s, but bird “B” shows no pale area on the throat. This bird is also a Pelagic Cormorant.

This close-up of two Brandt’s Cormorants (on the left and right) and a Pelagic Cormorant (middle) show the differences in head and neck proportions and bill size that allow them to be separated at a distance. This cropped image also shows the paler tan feathering on the throats of the two Brandt’s, while the Pelagic is completely dark-faced.

Those of you who responded publicly were quite successful in correctly identifying these cormorants. The apparent size of bird “B” was understandably confusing to a couple of respondents. We hope that this exercise will aid you in your efforts to separate distant cormorants during your next visit to the Pacific Coast. If you have a group photo that includes several similar species, please send it our direction. We hope to make this sort of ID Challenge a regular feature of the BirdFellow.com journal.

Photo taken by David Irons using a Panasonic Lumix DMC-FZ8