Common Shag (the Mediterranean subspecies is endemic in the Mediterranean, Phalacrocorax aristotelis desmarestii) is a typical sea bird whose life cycle depends on the fish it feeds on, and on the islets and cliffs where it nests.
It's almost always on the sea and very rarely visits bigger ports and towns or wanders in the interior.
This bird is protected through the Nature Conservation Act, it's endangered at the European level (Addendum I of the EU Birds Directive) and is also on the Red List of the Birds of Croatia. Our park has about a 150 breeding pairs.
Common Shag is endangered because of its colonial way of life, and it can be an excellent indication of the biodiversity of sea and island eco-systems for it is at the top of the food chain.
Description of an adult bird:
Black feathers with green metallic sheen, the black edges of the feathers give them scaly appearance. The beak is black with yellow edges, eyes emerald green with a narrow yellow ring. Legs and feet are black.
Juveniles have a brown upper part of the body, the chin is whitish turning into brown towards throat. The belly is lighter. Traces of brown feathers are visible up to three years of age.
Because of this difference in appearance, many people think it's two different species but it's not true. It's just a difference in age. Common Shags are not such excellent fliers (unlike, for instance, peregrine or seagull) and it's obvious from where we found our ringed birds. They slowly wander along our coast of the Adriatic through Slovenia to Italy and back.
Common Shags eat fish, either individually or in a group.
Hunting fish, they can dive down to 50 metres below the sea.
The average speed of diving can be 2 metres per second.
They can live on their fat for about two weeks.
Their nest is 45-55cm in size, and beside the "classic" nest material can contain bits of fishing nets, plastic and other bits of flotsam.
In some parts of Japan and China there is a thousand year old tradition of using tame shags to fish in fresh waters. Of course, such a way of fishing (terribly complicated and economically unprofitable) is now used only for tourist presentations of the tradional way of life.