Double-crested Cormorant
The Double-crested Cormorant (Phalacrocorax auritus) is the most widespread and abundant of the 6 cormorant species found in North America. It is a common inhabitant of seacoasts and inland water. While closely associated with water, it is rarely found far from land. It is the only cormorant found throughout most of the interior parts of North America.
What it looks like
The Double-crested Cormorant is a large dark bird, with a long, kinked neck, small head, with a yellow-orange face and a long bill of the same color with a hooked end. It has a short tail and long wings. Its legs are far back on its body, requiring it to stand upright. The name “double-crested” is somewhat misleading, since the crest is only visible during breeding season, and it is black in most areas making it hard to see. Alaska birds have a much more apparent white crest. Four cormorants are pictured here on Florida’s Sanibel Island, along with a Brown Pelican and an invasive Iguana.
First year Double-crested Cormorants are lighter on the neck, breast, and belly contrasting with darker back, wings, and tail. The two juveniles, shown here, were taking a break after fishing at Blackwater National Wildlife Refuge in November 2020.
Take a look at their feet. Notice how all 4 toes are connected by a web. It’s called totipalmate feet, from the latin totus for complete and palmate for shaped like a hand, like your palm.
Breeding Behavior
Cormorants are gregarious birds, often nesting in large numbers at diverse sites. Nest sites include natural vegetation such as trees or shrubs, artificial structures such as navigation markers or bridge spans, or the ground on islands free from predators. Pictures of all three types are shown here.
Cormorant colonies are conspicuous due to the visible whitewash but, even more so, due to the powerful downwind reek of guano and rotting fish.
Cormorants form new pair bonds each year (seasonally monogamous). The male selects the nest site and attracts a female. The male carries in nesting material, while the female is in charge of actual nest construction.
Nest sites are used for many years in a row, although not necessarily by the same male. Over time, guano accumulates at the base of the tree hosting the nest. The powerfully acidic guano often kills the tree by changing the soil chemistry.
Cormorants typically lays 4 eggs, ranging from 1 to 7. Both sexes incubate the eggs for about 4 weeks until they hatch. The young are feeble upon hatching, weighing only about an ounce. They grow rapidly, though, soon gaining about a pound a week for the next 3 to 4 weeks until they are able to leave the nest, walking or swimming. They are able to fly when they are about 6-8 weeks old.
Diving and eating
When not nesting, Cormorants divide their time between eating and resting. They dive for their food, using their powerful, totipalmate feet to propel them underwater. They keep their wings at their side when diving — the wings are too long to be useful and would just get in the way underwater. They chase prey through the water, using their long bill with the hooked beak to catch fish. They typically swallow fish underwater, but will bring larger fish to the surface if they are too big to swallow immediately.
Although the Cormorant diet consists almost exclusively of fish, generally slow moving or schooling species, they also consume other aquatic species such as crustaceans, insects, eels, and amphibians. While there isn’t much research documenting their consumption of snakes, I ran across this injured Cormorant in a wildlife rehabilitation center just outside of Key Largo, FL. It was in an outside caged pool, and apparently a water snake decided to enter the area, giving this cormorant a special treat.
After a bout of fishing, Cormorants will often fly to a nearby spot of land or find a branch to perch on. They will then turn their back to the sun and spread out their wings, allowing them to dry in the sun. This is a common sight when Cormorants are around.
Conservation
Cormorants have had a rough time over the last 150 years. In the late 1800s through the first part of the 1900s they were viewed as threats to the fishing and aquaculture industry. Wildlife managers destroyed eggs in nests or shot them outright to reduce their numbers. Then starting in the mid 1900s, they suffered the effects from DDT and numbers continued to plummet, with the Cormorant listed as endangered in some states. Their numbers have since rebounded, but the practice of culling up to 160,000 Cormorants a year continues.
That’s it for this week.
Next week I’ll talk about the Bewick’s Wren.
If you missed last week’s bird, read about the Prairie Warbler here.