Brooklyn Bird Watch: April 18

Double-crested Cormorant. Scientific Name: Nannopterum auritum

April 18, 2022 By Joseph Palmer

Photo by Heather Wolf

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Today, Brooklyn Bird Watch features a Heather Wolf photo of the Double-crested Cormorant, seen in Brooklyn Bridge Park. When I’m in Florida and visit a pier I often see these birds on the edge of the pier drying their outstretched wings. The Cornell lab calls them “prehistoric-looking” with orange and yellow facial skin. Although from a distance they appear to have no special markings that would make them stand out visually like some birds, they have some fascinating features. For example, the inside of their mouths is bright blue and they have very exotic looking aquamarine eyes that “sparkle like jewels.”

Although they are called double-crested, you only see this feature during the breeding season. And once you hear one of these birds you’ll never make the mistake of thinking it might be a song bird. They make croaks and gargling sounds. To hear these croaks and gargling sounds might not be very pleasing, compared to a Cardinal or a Mockingbird, but to another cormorant, it’s could be just what they like to hear.

Cornell says they are “experts at diving” and will dive to depths of 24 feet and stay underwater for more than a minute.

Why they have to dry their wings in the sun is because they have less “preen oil” than other birds, so instead of shedding water like a duck, their wing feathers get soaked during a dive. Although this might seem that it would be a problem for a bird that spends its life in water, Cornell believes the wet feathers might help it with speed and agility for fishing underwater.

Pesticides can impact a bird species population. The Double-crested Cormorant population has had ups and downs, for example, ornithologists speculate that the population decline throughout the 1960s was caused by the persistent use of pesticides, especially DDT. Audubon informs us that once DDT was banned in 1972, their numbers started to increase again, and that trend continues today.

The accumulated fecal matter of the Double-crested Cormorant, known as “guano,” can kill the tree the birds are nesting in. When this happens, they usually move to nesting on the ground.

When they nest on the ground the nest is exposed to direct sun so the grownups shade the chicks and give them water by pouring the water from their beaks into the chick’s mouths. In a breeding colony, when the nests are placed on the ground, young cormorants leave their nests and congregate in groups with other youngsters and return to their own nests when it’s time to eat.

Like other birds, the Double-crested Cormorant uses a variety of items to build its nest. Primarily made of sticks mixed in with all kinds of things like deflated balloons, rope, junk, fishnet and lots of plastic debris, and they will even use parts of dead birds. Sometimes large pebbles have been found in the nest and ornithologists believe the Cormorant treats these objects as eggs.