The Great Cormorant (Phalacrocorax carbo) is the largest species of cormorants in Romania and its population numbers 20 000 pairs of birds.

The inhabitants of the Delta consider it a great enemy. This species fishes in large groups of almost 500 specimens.

On average, a cormorant measures 91 cm. During flight it holds its neck stretched and the flock is either linear, either 'V' shaped. Its plumage is bright black and its eyes are green. During pairing season, on its legs, appear two white and round spots.
This bird feeds in large groups, alongside the common pelican. Its nourishment consists of species like the carp or the Prussian carp. The great cormorant cannot swallow fish that are larger than 20 cm. However, its massive and strong beak allows it to catch up to 1 kg of fish, which are consumed later on.

This species nests during early springtime, in mixed colonies, alongside the pygmy cormorant and the heron. The female lays 4 blue eggs. The incubation of the eggs lasts 30 days. The chicks are able to fly after their first month of life.

The great cormorant is a good swimmer and a good diver. It can remain underwater for up to 70 seconds. Due to its swimming abilities, in China, this bird is used for sportive fishing.

Its main enemy is the white-tailed eagle, which hunts the cormorants right after they fish and their wet feathers do not allow them to fly. Also, the hooded crow attacks the colonies, destroys the eggs and kills the chicks.
Tourism is disturbing for the cormorant colonies.