European shag

The European shag, also known as the common shag, is a medium-large seabird.

It belongs to the cormorant family. This bird is unique because it is the only member of its own genus, Gulosus. The name Gulosus comes from the Latin word for glutton. The species name, aristotelis, honors the famous Greek philosopher Aristotle. Shags are important members of coastal ecosystems. They live near the rocky coasts of western and southern Europe. They also inhabit parts of southwest Asia and north Africa. Most birds stay within these breeding ranges during the winter.

Scientists have recently changed how we classify this bird. For a long time, shags were placed in the genus Phalacrocorax. However, a study in 2014 revealed they were quite different. Researchers found the shag was significantly more diverged than other groups. It is considered basal to the clade containing Nannopterum and Leucocarbo. This means it sits at a foundational branch of that group. Because of this, the bird was moved to its own genus, Gulosus. The International Ornithological Committee (IOC) accepted this change in 2021. Scientists believe Gulosus split from other groups between 9.0 and 11.2 million years ago.

There are three recognized subspecies of the European shag. The first is G. a. aristotelis, which lives in northwestern Europe along Atlantic coasts. The second is G. a. desmarestii, found near the Mediterranean and Black Seas. The third is G. a. riggenbachi, located on the northwest African coast. These subspecies show slight differences in their bill size. They also differ in the color of the legs and breasts of young birds. Recent evidence suggests another group may exist. Birds on the southwest Atlantic coast of Europe might be a new, undescribed subspecies.

An adult European shag is a striking bird. It is black with a long tail and a wide wingspan. One of its most recognizable features is a yellow throat patch. During the breeding season, adults grow a small crest on their heads. Their feathers often have a metallic green-tinged sheen. This sheen is why some people call them "green cormorants." You can tell them apart from the great cormorant by several traits. Shags are smaller and have a lighter, narrower build. Their bills are also thinner. Additionally, a shag's tail has only 12 feathers, while a great cormorant has 14.

The European shag is a highly skilled pursuit-diving seabird. It is one of the deepest divers in the cormorant family. When it prepares to dive, the bird jumps out of the water first. This movement provides extra impetus to help it plunge downward. Shags are primarily benthic zone feeders. This means they hunt for prey on the sea bottom. They can travel many kilometers from their roosting sites to find food. Their most common prey is the sand eel.

Shags rely on aerobic diving to hunt effectively. This means they depend on oxygen stored in their lungs and bloodstream. In UK coastal waters, typical dives last between 20 and 45 seconds. Between these dives, the birds take a recovery period of about 15 seconds. Researchers have used depth gauges to record their diving habits. Studying their diet is a major area of scientific interest. This is because scientists can easily collect samples through regurgitated food or pellets. At the Isle of May in Scotland, researchers studied a colony from 1985 to 2014. They found that chick diets changed as the ocean warmed. Shags used to be sandeel specialists, but they now eat a more diverse range of prey.

Nesting and reproduction require great effort from the parents. Shags nest on rocky ledges, in crevices, or inside small caves. Their nests are untidy heaps made of twigs and rotting seaweed. They use their own guano, or bird droppings, to cement the nest together. The nesting season is quite long. It begins in late February, but some nests are not started until May or later. A female typically lays three eggs. The chicks hatch without any down feathers. Because they lack insulation, they rely entirely on their parents for warmth. This continues for about two months before they can fly. Fledging usually happens between early June and late August.

The European shag is widespread across many coastal regions. During the breeding season, from late April to mid-July, you can find them in many places. These include the Saltee Islands in Ireland and the Farne Islands in England. They are also found in Norway, Iceland, Denmark, and Croatia. In 2015, the British population was estimated at 18,000 pairs. The largest single colony is located in the Cíes Islands in Spain. This massive colony contains 2,500 pairs of birds. In April 2017, eight new shags were even recorded being born in Monaco.