Adult Double-crested Cormorant, *Image by Ray Rozema*

This month, let’s talk about a bird that’s often seen around the Sacramento Valley near bodies of water, the Double-crested Cormorant. Double-crested Cormorant is the most widespread and common cormorant species in North America. Cormorants are active during the daytime (or diurnal). You may find Double-crested Cormorants along with herons, geese, and ducks; but they are not closely related to them. Bird experts have placed cormorants in a separate bird family or group. Double-crested Cormorants are found in Alaska, the continental United States, Mexico, Caribbean Islands, and Central America. Many nest along coastlines; but they also nest inland where there is a body of water nearby. While some Double-crested Cormorants live in California’s Central Valley year-round, many populations are migratory. Large flocks will migrate in a messy V formation and frequently winter along the Pacific, Atlantic, and Gulf coasts.

Double-crested Cormorants may be seen swimming alone and often will swim in open water areas, such as the middle of a lake. They are also seen in small or large sized flocks when both nesting and feeding. It can be easier to observe Double-crested Cormorants out of water because sometimes only their necks and heads are visible when they swim. They often will perch with their wings outstretched. Double-crested Cormorants do this to dry their feathers. Unlike duck feathers, their feathers are not fully waterproof. However, it has been suggested that not having waterproof feathers is a benefit for Double-crested Cormorants. Their wet feathers make them very fast and agile when they chase prey underwater.

There have been times in U.S. history when the population of Double-crested Cormorants has decreased to very low numbers. In the 1920’s, Double-crested Cormorants were killed and generally disliked. It was thought that they consumed too many fish. The population of Double-crested Cormorants also declined when the pesticide DDT was used in the 1960’s. In addition, the species has been negatively affected by oil spills and the exposure to other types of water contamination. After the use of DDT ended and the U.S. government made laws to protect wild birds, Double-crested Cormorants began to thrive again. Their numbers are now continuing to increase markedly. However, some fishing industries currently blame Double-crested Cormorants for depleting fish populations. Huge flocks can suddenly fly in and congregate at fish hatcheries or near commercial fishing areas. Studies have shown that a single cormorant can eat 1.5 pounds of fish per day. In a few regions, it is also believed that Double-crested Cormorants may be crowding out other colonial birds, such as herons. However, many scientists believe Double-crested Cormorants do not cause the negative impact that some people think to be the case. These scientists feel that the species is being treated unfairly or cruelly once again.

What do Double-crested Cormorants look like?

Double-crested Cormorants, *Image by Daniel Lee Brown*

Double-crested Cormorants are in-between the size of a crow and a goose and have a wingspan of about four feet. Both males and females look alike; however, male birds are usually slightly larger. Adult Double-crested Cormorants have black (or brownish-black) feathers and in certain lighting they have a greenish or bronze sheen. They have a yellow-orange area of bare skin on their faces and throats (called the gular area) which extends to the lores (the facial area on birds that’s in front of their eyes and next to their bills). They have teal (or aquamarine) colored eyes and the lining inside their mouths is also a bright blue color. Double-crested Cormorants have long bodies, wedge-shaped tails, small heads, relatively short legs and wings, and slender bills. Their long necks frequently appear to be bent or s-shaped. When double-crested cormorants fly, they pull their necks inwards creating a bent neck appearance. The necks of other cormorant species in the western U.S. appear straight during flight.

As the nesting season approaches, adult Double-crested Cormorants develop a curled, double crest of feathers on their heads. Their crests of white or black feathers (crest feather color is specific to each subspecies) stick out away from their heads and curve backwards, making them very unique-looking birds. Double-crested Cormorants also develop blue eyelids and their throat area turns deep orange during this time. Some people describe them as being ‘prehistoric’ looking.

Juvenile (or immature) Double-crested Cormorants have pale necks and spotted white (or pale-gray) upper chests. Their backs, wings, and tails are brown. Juveniles also have a yellow bare skin area on their faces.

Double Crested Cormorant, *Image by Mary Forrestal*

Where do Double-crested Cormorants live?

Double-crested Cormorants are very adaptable and live in many types of water habitats, either in fresh or saltwater. They are found near rivers, ponds, reservoirs, swamps, lakes, and in coastal areas. Double-crested Cormorants require water for feeding and sturdy perches to rest or dry off, such as rocks, dead tree tops, or docks.

Double-crested Cormorants form nesting colonies between May and July. They nest in trees or shrubs that are frequently near or in water, on sea cliffs, on platforms, among flooded logs, or on the ground where there are no sturdy trees. Pairs work together to repair an old nest or to build a new one. Usually it’s the male that brings in materials for nest building and the female does the nest construction. The simply-constructed nests are 1.5 to 3 feet in diameter and are made out of sticks and plant material. It is reported that Double-crested Cormorants will use pieces of trash when constructing their nests. Both parents will sit on the eggs to keep them warm (or incubate the eggs). After hatching, both parents feed the young and bring water to them using their bills.

Double-crested Cormorants parents frequently will use their bodies to shield the eggs or their young from the sun, since their nests are not normally under cover. The young leave the nest 3-4 weeks after birth, learn to fly at about 5-6 weeks of age, and are completely independent when they reach about 9-10 weeks of age. They will start nesting when they are around 2-3 years of age.

What do Double-crested Cormorants eat?

Double-crested Cormorant, *Image by Daniel Lee Brown*

Double-crested Cormorants are carnivorous (or flesh-eating). They mainly eat fish and hunt by swimming and diving. Double-crested Cormorants are very skillful at catching their prey when they dive into water. They use their wings for steering and their powerful webbed feet to quickly propel their bodies underwater. Double-crested Cormorants will also eat insects, crayfish, crabs, shrimp, frogs, salamanders, and eels. Occasionally they will eat plant material and snakes. Because the tips of their upper bills are shaped like a hook, it is easy for them to catch and manipulate their prey for eating. Double-crested Cormorants generally eat smaller fish underwater; but they bring larger fish up out of the water prior to eating them. They actually flip fish into the air and then swallow them head first!

What do Double-crested Cormorants sound like?

Double-crested Cormorants are often silent. However, they do use calls to communicate with each other. Their calls are described as hoarse, bull-frog-like grunting sounds.