December’s Bird-of-the-Month: Double-crested cormorants

Double-crested cormorants have returned to the Apex Reservoir. It’s not that they’ve been absent for any period of time, it’s just that a large flock has returned. I can see cormorants much of the year, but the more common sighting is of just a pair or two. But come December, the past two years at least, double-crested cormorants at Apex Reservoir can number in the hundreds.

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One seagull amidst a gathering of double-crested cormorants in Apex, NC

They love the NC Wildlife Resource Commission’s automated fish feeders, of course. Though these birds hardly need any help catching fish, they don’t mind us making the task a little easier. The Cornell Lab of Ornithology (https://www.allaboutbirds.org/guide/Double-crested_Cormorant/id) reports that cormorants eat more than 250 different kinds of fish. They will occasionally eat a crustacean, an insect, or an amphibian. When eating crustaceans, they’ve been seen flipping the animal up in the air and catching it headfirst to make it easier to swallow.

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Double-crested cormorants waiting for fish.

 

The double-crested cormorant is a large, colonial black bird, up to a yard long with a wingspan that can stretch to four feet. It has a beak that starts from a yellowish throat patch and extends forward three or four inches. With binoculars you can see the slight downward hook at the end of its upper bill that it uses to catch fish.

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Portion of a large gathering of double-crested cormorants on the Apex Reservoir, NC

Young birds are brownish with pale breasts. The birds nest in colonies, and the young often cluster together in groups called a creche. Only a mature, breeding male exhibits the “double-crest,” which I’ve never seen. The oldest reported double-crested cormorant was banded in 1984 in Canada and recovered 22 years later in Louisiana. Cormorants will return to the same nesting areas year after year, and in some much-used locations trees have toppled due to the accumulated weight of nest after nest. Large pebbles frequently find their way into a cormorant nest, and the birds will treat these pebbles as they would an egg.

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Three double-crested cormorants, low in the water, necks riding high.

Most of the year, cormorants on the Apex Reservoir may be found floating low in the water, their long necks the most conspicuous feature. The beak and head will usually be pointed slightly up. Oftentimes a pair will be separated by a few yards to a few dozen yards. One at a time the birds will take turns fishing. A bird will thrust its beak forward and down, surface diving underwater, disappearing for what seems like at least a minute or more. It will resurface twenty to forty yards away.

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Double-crested cormorant in flight

With all four toes connected by webbing, and powerful wings, the double-crested cormorant makes a powerful underwater swimmer, and a dangerous predator, if you’re a fish. Though I’ve never seen it swim underwater, it reportedly beats both its webbed feet and wings to propel a streamlined body along after its prey.

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Cormorant landing on the Apex Reservoir, NC.

An interesting behavior I have seen is a cormorant drying its wings in the sun. Cormorants apparently have less oil in their feathers, which means their wings get soaked when swimming. Although this means they have to make the effort to dry out their wings, it may also help them swim faster underwater. Perhaps due to the time it takes to dry their feathers after fishing, cormorants often spend half their day perched above the water on an overhanging branch or rock.

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Double-crested cormorant drying its wings

The double-crested cormorant, scientific name Phalacrocorax auritus, is related to frigatebirds and boobies, winters along the shorelines of North America, and summers on inland lakes. In the past the birds suffered from overhunting and pesticide exposure. DDT thinned their eggshells, leading to reproductive failure. Since the 1970s, double-crested cormorant populations have rebounded, in some areas colony sizes doubling in five years.

Although I’ve never identified one, neotropic cormorants will sometimes mingle with double-crested cormorants. The former species is the smaller of the two, and the space immediately forward of its eyes is covered with black feathers rather than the pale featherless skin found in the double-crested cormorant.

 

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