European shags have a large range and population estimates are approximately 260,000 to 290,000 individuals. Large population declines have not been documented and they are considered "least concern" by the IUCN. They are often entangled and killed in fishing gear and nets or are intentionally killed by fishermen. They are vulnerable to the impacts of coastal pollution, such as oil spills.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
European shags are preyed on by introduced American mink (Neovison vison) at some nesting colonies. Other predators are not reported, but probably include coastal raptors, like white-tailed eagles (Haliaeetus albicilla, and avian nest predators such as gulls or corvids. Their nesting habits on steep, rocky, coastal cliffs, prevent some predation.
Known Predators:
European shags are from 65 to 80 cm in length and 90 to 105 cm in wingspan. They average 2 kg in mass. They have black plumage overall with greenish iridescent hues. They have black feet, legs, and bill, with bright yellow skin at the base of the bill and bright turquoise eyes. They have a small, single, black crest that develops in the breeding season, when they also develop their most intense green hues to the plumage. Non-breeding adults have duller plumage with a pale chin, mottled plumage on the throat, and the bill becomes yellowish. Juveniles are uniformly brown and have pale areas on the head and underparts. They are similar in appearance to great cormorants (Phalacrocorax carbo), but are overall smaller.
Average mass: 2 kg.
Range length: 65 to 80 cm.
Range wingspan: 90 to 105 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Maximum lifespan is not reported for European shags, but studies demonstrate that most mortality occurs in the first year of life as a direct result of lower foraging efficiency. Other significant sources of mortality are accidental and intentional deaths through entanglement in fishing gear and persecution by humans.
European shags are found along rocky, marine coastlines and islands and are never found very far from land or very far inland. Preferred foraging grounds are in clear, protected waters over sand or rocky substrates, such as in bays or coastal channels. They avoid fresh, brackish, or muddy water.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: coastal
European shags are found throughout western Europe, from Iceland, the British Isles, Portugal, Gibraltar, and northern Africa east to Greece and north into the Ukraine and as far north as Norway. There are 3 recognized subspecies: P. a. aristotelis occurs from Iceland to Scandinavia and south to the Iberian Peninsula, P. a. desmarestii occurs in the central Mediterranean to the Black Sea, and P. a. riggenbachi occurs along the coast of North Africa.
Biogeographic Regions: palearctic (Native )
European shags often forage alone, but will form large foraging flocks of several hundred when prey conditions allow. They eat almost exclusively small fish, although they will also eat crustaceans, cephalopods, and polychaete worms. Common fish prey include Gadidae, Clupeidae, Cottidae, Labridae, Ammodytes, and Trisopterus species. European shags don't hunt cooperatively and generally dive and pursue their prey under water. They perform a distinctive "leap" before diving into the water. European shags forage in deeper water and tend to eat different types of fish than great cormorants (Phalacrocorax carbo), with which they co-occur.
Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans
Primary Diet: carnivore (Piscivore )
European shags are susceptible to Newcastle disease. They are important predators of small fish in their coastal habitats.
European shag eggs, young, and adults are sometimes taken from nests or hunted for food.
Positive Impacts: food
European shags are persecuted because of the perception that they interfere with commercial or subsistence fishing, although they eat mainly small fish so are unlikely to compete directly with humans for prey. They may interfere at hatcheries.
European shags produce a variety of grunting and clicking vocalizations, which can be heard at the RSPB site. Other forms of communication are not well documented, but European shags may use visual displays in mating like other cormorants.
Communication Channels: acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
European shags are sometimes placed in the genus Stictocarbo. They are also known as common shags, green shags, or green cormorants. In French they are known as Cormoran huppé, in German they are called Krähenscharbe, and in Spanish they are called Cormorán Moñudo. The name "shag" comes from the Old Norse word "skegg" for "beard," possibly referring to the crest.
European shags are monogamous and pair-bonds often last over successive years. Pairs re-use their nests regularly.
Mating System: monogamous
European shags build nests of sticks, seaweed, and other marine debris on rocky ledges, cliffs, or stacks. Nests have been found from just above the high water level to 100 m above the sea. Nesting areas host large concentrations of these birds, who nest in close proximity. Nests are said to have an intense, unpleasant smell, especially as the seaweed rots. Larger nests have higher success rates than smaller nests and nests on narrow cliffs are less successful than those in other areas. Breeding season varies regionally, with southern populations (Tunisia) breeding from November to February, Black Sea populations breeding from January to March, and northern Atlantic populations breeding from March through June. Females lay from 1 to 6 eggs (usually 3), usually begin incubation after laying the 2nd egg, and incubate them for 30 to 31 days. Hatchling European shags fledge at about 53 days, remain in the nest for 8 weeks after hatching, and are cared for by their parents for 15 to 50 days after they fledge. Within 30 days of hatching males are generally larger than females and the hatchling from the last egg laid is generally smaller. Females may breed as early as their 2nd year.
Breeding interval: European shags breed once yearly.
Breeding season: Breeding season varies with region, occuring between November and June throughout their range.
Range eggs per season: 1 to 6.
Average eggs per season: 3.
Range time to hatching: 30 to 31 days.
Average fledging age: 53 days.
Range time to independence: 68 to 103 days.
Range age at sexual or reproductive maturity (female): 2 (low) years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
European shag hatchlings are naked at hatching and develop brown down. They fledge at about 53 days old. Both adults protect and provide for their young, incubating them between their feet and breast and alternating duties. They continue to provide food for another 15 to 50 days after the young have fledged. At one site hatching success was from 69 to 73% and fledging success was from 67 to 95%. Most mortality of young is associated with food shortages.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female)
Accidental visitor.
The European shag or common shag (Gulosus aristotelis) is a species of cormorant. It is the only member of the monotypic genus Gulosus.[2] It breeds around the rocky coasts of western and southern Europe, southwest Asia and north Africa, mainly wintering in its breeding range except for the northernmost birds. In Britain this seabird is usually referred to as simply the shag.[3] The scientific genus name derives from the Latin for glutton. The species name aristotelis commemorates the Greek philosopher Aristotle.[4]
The European shag was formerly classified within the genus Phalacrocorax, but a 2014 study found it to be significantly more diverged than the clade containing Phalacrocorax and Urile, but basal to the clade containing Nannopterum and Leucocarbo, and thus classified it in its own genus, Gulosus.[5] The IOC followed this classification in 2021.[6] Gulosus is thought to have split from the Nannopterum-Leucocarbo clade between 9.0 - 11.2 million years ago.[5]
There are three subspecies:[7]
The subspecies differ slightly in bill size and the breast and leg colour of young birds. Recent evidence suggests that birds on the Atlantic coast of southwest Europe are distinct from all three, and may be an as-yet undescribed subspecies.[8]
The name shag is also used in the Southern Hemisphere for several additional species of cormorants.
This is a medium-large black bird, 68 to 78 cm (27 to 31 in) long and with a 95-to-110-centimetre (37 to 43 in) wingspan. It has a longish tail and yellow throat-patch. Adults have a small crest in the breeding season. It is distinguished from the great cormorant by its smaller size, lighter build, thinner bill, and, in breeding adults, by the crest and metallic green-tinged sheen on the feathers. Among those differences are that a shag has a lighter, narrower beak; and the juvenile shag has darker underparts. The European shag's tail has 12 feathers, the great cormorant's 14 feathers. The green sheen on the feathers results in the alternative name green cormorant sometimes being given to the European shag.
It feeds in the sea, and, unlike the great cormorant, is rare inland. It will winter along any coast that is well-supplied with fish. The European shag is one of the deepest divers among the cormorant family. Using depth gauges, European shags recorded diving up to 61 m (200 ft) deep.[9] European shags are preponderantly benthic zone feeders, i.e. they find their prey on the sea bottom. They will eat a wide range of fish but their commonest prey is the sand eel. Shags will travel many kilometres from their roosting sites in order to feed.
In UK coastal waters, dive times are typically around 20 to 45 seconds, with a recovery time of around 15 seconds between dives; this is consistent with aerobic diving, i.e. the bird depends on the oxygen in its lungs and dissolved in its bloodstream during the dive. When they dive, they jump out of the water first to give extra impetus to the dive.
It breeds on coasts, nesting on rocky ledges or in crevices or small caves. The nests are untidy heaps of rotting seaweed or twigs cemented together by the bird's own guano. The nesting season is long, beginning in late February but some nests are not started until May or even later. Three eggs are laid. Their chicks hatch without down and so they rely totally on their parents for warmth, often for a period of two months before they can fly. Fledging may occur at any time from early June to late August, exceptionally to mid-October.
The shag is a pursuit-diving seabird that feeds predominantly in benthic habitats. Due to the relative ease with which diet samples can be collected from this species (regurgitated food or pellets) and the perceived conflict between the Phalacrocoracidae and fisheries, shag diet competition has been the subject of substantial scientific interest.[10][11][12][13] Evidence collected at one colony, the Isle of May, Scotland, between 1985 and 2014, suggests that shag chick diet composition in this population has diversified in response to ocean warming.[14] Shags also feed on fewer sandeel on windy days, presumably due to the strong effect of wind on flight in this species.[15] The year-round diet of full-grown shags at this colony has also changed over the past 3 decades, from sandeel specialists to an increasingly diverse prey base.[16]
The European shag can be readily seen among the following locations during the breeding season, between late April and mid-July: Saltee Islands, Ireland; Farne Islands, England; Isle of May, Deerness and Fowlsheugh, Scotland; Runde, Norway; Iceland; Denmark; Faroe Islands; Galicia, Northern Spain; Dalmatia and Istria, Croatia. In April 2017, eight new European shags were born in Monaco.[17]
The largest colony of European shags is in the Cíes Islands, Spain, with 2,500 pairs (25% of the world's population).
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Composite image of the bird jumping into the sea in Malinska, Croatia
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G. aristotelis diving
Eggs, Collection Museum Wiesbaden
Young European shag in Croatia
European shags in breeding plumage, Snæfellsnes, Iceland
The European shag or common shag (Gulosus aristotelis) is a species of cormorant. It is the only member of the monotypic genus Gulosus. It breeds around the rocky coasts of western and southern Europe, southwest Asia and north Africa, mainly wintering in its breeding range except for the northernmost birds. In Britain this seabird is usually referred to as simply the shag. The scientific genus name derives from the Latin for glutton. The species name aristotelis commemorates the Greek philosopher Aristotle.
