What Do Cormorants Eat? (Complete Guide)

There are 40 species of cormorants and cormorants Coral Branch, of which about 20 contain the word “cormorant” in their common name. The cormorant is a prehistoric water bird with a large hooked beak and broad webbed feet that lives on nearly every continent. Here, we’ll answer the question: What do cormorants eat?

Cormorants are opportunistic predators that eat almost exclusively fish. Almost every species of heron or cormorant eats fish and aquatic animals such as shrimp, crustaceans, molluscs, crustaceans, and other shellfish, and occasionally octopus or squid. Most cormorants are generalists, feeding on whatever aquatic prey they can find in their feeding areas.

Cormorants are particularly adept at catching fish and combine a variety of prey-catching techniques, such as swallowing smaller prey whole while whistling through shallow waters, or diving to great depths to catch prey. Emperor cormorants have been recorded diving to a depth of 80 meters!

Due to their excellent fishing ability and sometimes voracious appetite, cormorants can be a nuisance to fishermen and anglers, and anyone who wants to maintain a fishery or pond. A large flock of cormorants can deplete a waterway of fish in just a few hours!

Read on to learn more about the feeding habits and diet of these amazing fishing birds!

One of the main components of a cormorant’s diet is fish

What fish do cormorants eat?

Cormorants eat any fish they can catch and swallow. This includes pretty much any small to medium fish they get from their feeding grounds, including minnows, shad, herring, gobies, trout, bass, and panfish.

Cormorants are generalist predators that can hunt a wide range of fish or a relatively small number of fish. For example, in France and Scotland, about 18 to 22 species of fish are featured on the typical great cormorant diet, while in North America, some cormorants mainly feed on salmon and salmon throughout the year.

Some of the larger prey items include pike, Atlantic salmon, catfish, and carp. A great cormorant was found devouring a 9-inch grass carp and another was recorded catching an Atlantic salmon weighing around 1.5kg or more! Great cormorants also eat eels and have been documented to catch very large specimens up to 50 cm long.

Smaller species of cormorants, such as lesser cormorants and pygmy cormorants, eat higher proportions of smaller fish and amphibians. For example, young cormorants eat tadpoles and young amphibians.

Swarms of cormorants can have devastating effects on fish populations. In the Great Lakes region, for example, cormorants can reduce the populations of certain fish species by about 80 to 90 percent.

great cormorant fishing

How much fish do cormorants eat a day?

Great cormorants usually aim to eat about 1 lb (0.5 kg) of fish per day. This could include 15 to 30 smaller fish or just one larger catch.

While cormorants are capable of eating large prey, studies have shown that their average prey length is less than 20 cm (at least for great cormorants). Large cormorants can eat about 30 fish a day.

How do cormorants catch fish?

Cormorants primarily catch prey by diving below the surface, a technique known as “chase diving”. The prey is either swallowed whole or stuck in the mouth and transported to land where it is killed, eaten or swallowed alive. Cormorants have wide-open, hooked mouths that help them scoop up and swallow fish efficiently, and webbed feet that help them maintain high speeds in the water.

Most dives are shallow (1 to 2 meters deep), but some cormorants have been recorded diving to depths of 20 meters or more. Emperor cormorants, or imperial cormorants, have been recorded diving to an incredible depth of 80 metres, but the more typical maximum depth is 5 to 10 metres. Cormorants generally prefer diving in clear waters, but are also successful in foraging in murky or uncharted waters.

Cormorants are nimble at catching fish, and some cormorants also catch fish and other prey from shallow waters rather than diving below the surface, although this is less common. They tend to forage in short bursts, initiating about 10 to 25 dive trips in bouts of up to 25 minutes. In summer, great cormorants fish for about 5 hours, but in winter they may shorten their fishing time to as little as 45 minutes.

cooperative fishing

Cormorants usually fish alone in small or large groups, but they have also been documented to hunt and prey cooperatively. Cormorants will drive small schools of fish to shore where they are easier to spot and catch. This process will be repeated until most cormorants have enough food.

black cormorant diving for fishing

How do cormorants forage?

Cormorants usually have no trouble finding food. They flock to fish-rich lakes, estuaries, rivers, reservoirs, and coastal environments, and are able to fish in a variety of shallow and deep waters, fast-moving waters, and rock pools.

In general, most cormorants do prefer clear, slow-moving waters, but they are also happy to fish in a wide range of habitats. Once a colony or flock of cormorants has established a reliable feeding ground, they return there after their annual migration.

What time of day do cormorants eat?

Studies have shown that cormorants feed primarily at dusk and dawn, and rarely in the late morning and mid-afternoon periods between 10:00 am and 3:00 pm. However, nocturnal feeding has also been reported.

In winter, cormorants are more likely to extend their feeding time into the night if they haven’t caught anything during the day.

In general, cormorants feed when fish are closer to the surface and easy to spot, and when they are less active and moving more slowly, which is more common in the morning and dusk. However, as opportunistic predators, cormorants are mostly flexible when it comes to feeding timing.

A flock of cormorants fighting for a fish

What do cormorants eat in winter?

A cormorant’s diet varies by region and season, and they will eat whatever fish is available in their wintering grounds. This includes anything from salmon and herring to bass, minnows, sticklebacks, sunfish, carp and catfish.

Cormorants eat less in winter, but also reduce foraging trips to save energy. While foraging can last for hours in summer and spring, Norwegian great cormorants cut their daily foraging time to less than 60 minutes and often eat less fish per day.

In North America, cormorants often visit inland reservoirs during the winter, where they feed on some freshwater crustaceans such as catfish, shad, sunfish and crayfish.

What do cormorants eat in summer?

During the summer, cormorants feed on a wide variety of fish. Different cormorants occupy different habitats and have different diets, although there is some crossover. For example, North American double-crested cormorants eat more eels in summer than great cormorants, which eat more non-eels.

Smaller cormorants, such as the lesser cormorant, take advantage of spring and summer amphibian breeding opportunities, increasing tadpole intake.

Double-crested cormorant (Phalacrocorax auritus) in flight

How do cormorants help fishermen?

Cormorants have been used for thousands of years for traditional human fishing purposes. Cormorant fishing involves tying a net around the bird’s throat and setting out to catch fish.

Cormorants can still swallow small fish, but any larger fish will be caught in the net tied around the neck and cannot be swallowed. The bird then returns to the boat and the fisherman removes the fish from its gullet.

While cormorant fishing was once popular in some countries in Europe (such as North Macedonia and Greece), as well as in Japan and China, it is now rare. However, some traditional fishermen still use this technique in China.

A cormorant fisherman and his bird on the Li River in Yangshuo, Guangxi, China

What do little cormorants eat?

Young cormorants are fed a range of fish and other aquatic animals. Their parents partially digest their food, and the chicks tend to put their hands in their mouths as they regurgitate the food into their mouths.

Cormorants have large throat pouches and crops, which help them store large amounts of food. Chicks have a strong appetite and eat 200 to 300 grams of food a day (take great cormorants as an example).

cormorants feeding chicks

What do cormorants drink?

Cormorants drink water, and adults tend to get most of their water needs through feeding.

Since chicks do not dive on their own, but are fed by their parents, they can get very thirsty in hot climates. Cormorant chicks have been known to beg for water, which the parents store in their throat pouches and cut and feed them when they are particularly thirsty.

Cormorant Diet FAQs

What do double-crested cormorants eat?

The double-crested cormorant eats mainly fish, but also shellfish and even insects. On average, double-crested cormorants ate more eels than great cormorants.

What do flightless cormorants eat?

The unique flightless cormorant of the Galapagos lost its ability to fly during its evolution. However, its diet remains primarily piscivorous, consisting of fish, eels, octopus, squid, and other aquatic animals.

Do cormorants eat snakes?

Cormorants are opportunistic predators that prey on snakes in both freshwater and coastal habitats. In addition, many snakes are strong swimmers and may be found in cormorant feeding areas.

Do cormorants eat ducklings?

Certain species of cormorants have been documented to eat other birds, especially ducklings. However, this is not common.

A cormorant swallows a fish

Do cormorants eat mackerel?

Cormorants do eat mackerel, which make up a large portion of their diet in some parts of Europe and North America.

Do cormorants eat turtles?

Cormorants are unlikely to eat turtles, and there is no real evidence that they do.

Do cormorants eat frogs?

Many species of cormorants do eat frogs, especially those that forage in shallow inland waterways, lakes, and ponds.

Do cormorants eat crayfish?

Cormorants do eat crayfish and other shellfish, but crustaceans are not their main diet.