Double-crested Cormorants (Nannopterum auritum) are large yet sleek waterbirds with a kinked neck, black plumage, and fancy double crests during the breeding season.
They are skilled hunters, diving to depths of up to 26 feet, feasting primarily on fish. If you hear anything that oinks like a pig, but you are nowhere near pigs then you might have heard one! Here is some more information so you can be sure.
Identification
Double-crested cormorants are large waterbirds, measuring between 28 to 35 inches long with a 45-to-48-inch wingspan. They have heavy, but fairly lean and streamlined bodies. Their necks are long and thick and have a kink in it.
They walk on short but sturdy black legs and webbed feet. Their tails are wedge-shaped, and their wings are broad and rounded. In flight, they have a slight bend in the neck just before the head. The species has long dark bills with a hooked upper mandible.
Male and female Double-crested Cormorants look the same, but males are slightly larger than females on average. Adults have very dark brownish-black plumage, the only color being a small patch of yellow to orange skin on their upper throat, face, and base of the bill.
Their appearance changes slightly depending on the season. During the breeding season, adults develop tufts of stringy feathers on both sides of their heads just above the eyes. The tufts can be black, white, or a mix, depending on the subspecies and location. They also have blue eyelids, and the skin on their face is orange.
Non-breeding adults do not have crests or blue eyelids, and their skin is more yellow instead of orange.
Juvenile Double-crested Cormorants are fairly similar to adults. They are dark brown overall but have a pale whitish fore-neck, chest, and belly. Their bill is yellow with some dark coloring on the upper mandible.
Vocalizations
Double-crested Cormorants are mostly silent. They generally only vocalize during mating, aggressive encounters, or when landing or taking off. The range of their calls is also limited. Adults can give a series of deep guttural croaks, grunts, and gargles, sometimes mixed together. It is similar to an oinking or grunting pig. Nestling screech with high-pitched nasal but fairly clear calls.
Food
Double-crested Cormorants are carnivores. Their specific diet varies with season and place – in essence, they eat what is available. They primarily feast on fish with reports citing over 250 different species as their prey. However, they also eat insects, crustaceans such as crabs and shrimp, amphibians such as frogs and salamanders, snakes, mollusks, and sometimes also plant material.
Double-crested Cormorants forage singly or in groups in various bodies of water, from freshwater lakes and rivers to the sea. Hunting is generally done in shallow waters that are less than 26 feet deep and within 3 miles of the shore.
They dive underwater and usually remain at mid to upper levels, using their feet and sometimes wings to propel them forward to catch their prey. Dives last for around 30-70 seconds. They hunt schooling fish in large flocks.
Smaller prey is devoured underwater, whereas larger prey is brought to the surface to be cleaned and/or picked into smaller pieces before consumption. For example, if they capture a hard-shelled food item, like a crayfish, they bring it to the surface, smack it on the surface of the water to remove its legs, then throw it in the air and swallow it.
Nesting and Eggs
Double-crested Cormorants are monogamous and breed in colonies that can be mixed with other wading bird species and can become huge, up to thousands of pairs in size. Males are first to arrive on the breeding grounds and choose the nest site.
They then put on various courtship displays. On the water, they swim in zigzags, splash the water with their wings, and dive to find and present the female pieces of weeds. At the nesting site on land, males crouch, call, and vibrate their wings. After the pair bonds, they lose their crests.
Double-crested Cormorants nest near the water on the ground, on rocks, but possibly also in trees. The pair works on the nest together, with the male bringing materials and the female doing most of the building. Nests built on the ground are wider, whereas nests built in trees are deeper.
The platform is mainly built from sticks and twigs roughly the width of a finger, woven together with seaweed, flotsam, and other vegetation, and lined with grass. It measures 1.5-3 feet across and 4-17 inches in height.
The pair can have one to two broods in a year with 1-7, usually 3-4 eggs in a clutch. Double-crested Cormorant eggs are pale bluish-white, have a chalky coating, and measure 2.2-2.8 inches long and 1.4-1.6 inches wide. Incubation takes 25-33 days with both parents taking turns. They also share caring and feeding duties after the eggs hatch.
Young leave the nest about 3 to 4 weeks after hatching and can fly at around 6 weeks old. They can learn to dive at around the same time or slightly later and become fully independent 10 weeks after hatching.
Current Situation
Double-crested Cormorants range throughout most of North America and some coastal areas of Central America. Their breeding range extends throughout most of north-central North America, along the southern coast of Alaska, and the eastern coast of North America.
There are resident populations in Florida, coastal Pacific Northwest, and coastal Mexico. The populations that do migrate fly to the southern and southeastern United States and the Pacific Coast.
Double-crested Cormorants inhabit various inland and marine aquatic habitats. They are very adaptable and can be found along coasts, in bays, lakes, rocky coasts, mangrove swamps, small ponds, large lakes, and rivers. However, they would preferably require fairly safe areas to perch after diving.
Double-crested Cormorants are currently widespread and numerous, listed as of least concern on the IUCN Red List. Despite their ups and downs in the past due to hunting, pollution, and pesticides, their populations are currently increasing.
Facts About Double-crested Cormorants
- Double-crested Cormorants have five recognized subspecies that can be differentiated by the size, shape, and color of their crests. In general, western populations have whiter crests whereas eastern populations have darker ones.
- Double-crested Cormorants have less preen oil than other waterbirds so when they dive, their feathers get soaked. This is quite a nuisance for the birds since they often have to wait in the sun, wings spread, to dry before diving again.
- Accumulated excrement beneath the nests can kill the trees, in which case the pair moves to a new area or to the ground.
- Double-crested Cormorants have some interesting habits when it comes to nesting. They sometimes have large pebbles in their nests, which they treat as eggs. To cool down on hot days, they pour water over their offspring.
- Double-crested Cormorants live for 6 years in the wild on average. The oldest wild individual on record lived to be at least 23 years and 8 months old.
Similar Species
Double-crested Cormorants look similar to various other cormorant species, including the Neotropic Cormorant, Brandt’s Cormorant, Great Cormorant, Pelagic Cormorant, and Anhinga. Here are the three most similar species and how to tell which one is which.
Neotropic Cormorant
Neotropic Cormorants are resident throughout their range with only the northernmost populations retreating southward for the winter. In North America, they are generally restricted to the southern United States.
Adults are dark, seemingly black overall with an olive sheen to the wings, a white line outlining the chin, and have white tufts on the head during the breeding season. Juveniles are similar to adults but have brown chests, necks, and heads.
Compared to Double-crested Cormorants, Neotropic Cormorants have longer tails but are smaller. They do not have a bare face and have a white line outlining the base of their bill. Juveniles are dark overall whereas juvenile Double-crested Cormorants have a pale underside.
Brandt’s Cormorant
Brandt’s Cormorants are year-round residents along the western coast of the United States and Baja California with their wintering range extending further north and south.
Adults are black overall and breeding adults have a blue gular patch and blue eyes. Compared to Double-crested Cormorants, Brandt’s Cormorants are larger but have a shorter tail. Instead of bright orange skin, they have blue facial skin during the breeding season and black during non-breeding season.
Anhinga
In North America, Anhingas are residents along the southern coast of the United States, and their breeding range extends further inland.
Males are black overall, have silvery streaks on their back and wings, and a yellow dagger-like bill. Females have similar plumage but a paler brown head, neck, and breast.
Compared to Double-crested Cormorants, male Anhingas have longer tails, are more slender, and have a daggerlike instead of a hooked bill. They do not have colorful facial skin. In turn, Double-crested Cormorants lack the white streaks on the wings and back.
Frequently Asked Questions
What does the double-crested cormorant symbolize?
Double-crested Cormorants symbolize various things depending on the culture and location. They may symbolize positive things, such as good omens, wise spirits, regality, determination, and resilience, but also negative things, such as gluttony and evil.
Are cormorants pests?
Cormorants may be considered pests to aquaculture depending on location.
Is the double-crested cormorant a carnivore?
Double-crested Cormorants are carnivores who mainly feed on fish.
