| European shag | |
|---|---|
 | |
| European shag on a rock | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Suliformes |
| Family: | Phalacrocoracidae |
| Genus: | Gulosus Montagu, 1813 |
| Species: | G. aristotelis |
| Binomial name | |
| Gulosus aristotelis (Linnaeus, 1761) | |
 | |
| Range ofG. aristotelis Breeding Non-breeding | |
| Synonyms | |
Phalacrocorax aristotelis | |
TheEuropean shag orcommon shag (Gulosus aristotelis) is a species ofcormorant. It is the only member of themonotypic genusGulosus.[2] It breeds around the rocky coasts of western and southern Europe, southwest Asia and north Africa, mainlywintering in its breeding range except for the northernmost birds. InBritain thisseabird is usually referred to as simply theshag.[3] The scientificgenus name derives from theLatin for glutton. The species namearistotelis commemorates the GreekphilosopherAristotle.[4]
The European shag was formerly classified within the genusPhalacrocorax, but a 2014 study found it to be significantly more diverged than the clade containingPhalacrocorax andUrile, butbasal to the clade containingNannopterum andLeucocarbo, and thus classified it in its own genus,Gulosus.[5] TheIOC followed this classification in 2021.[6]Gulosus is thought to have split from theNannopterum-Leucocarbo clade between 9.0–11.2 million years ago.[5]
There are threesubspecies:[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 ofcormorants.
This is a medium-large blackbird, 68 to 78 cm (27 to 31 in) long and with a 95-to-110-centimetre (37 to 43 in) wingspan.[9][10] It has a longish tail and a yellow throat patch. Adults have a small crest in the breeding season. It is distinguished from thegreat cormorant by its smaller size, lighter build, thinner bill, and, in breeding adults, by the crest and metallic green-tinged sheen on thefeathers. Among those differences are that a shag is smaller and has a lighter, narrower beak,[9] and the juvenile shag has darker underparts. The European shag's tail has 12 feathers, as do the great cormorant's 14 feathers. The green sheen on the feathers results in the alternative namegreen cormorant sometimes being given to the European shag.[11]
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It feeds in the sea, and, unlike the great cormorant, is rare inland. It will winter along any coast that is well-supplied withfish.The European shag is one of the deepest divers among the cormorant family. Usingdepth gauges, European shags recorded diving up to 61 m (200 ft) deep.[12] European shags are preponderantlybenthic 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 thesand 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 theoxygen in itslungs and dissolved in itsbloodstream 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 rottingseaweed or twigs cemented together by the bird's ownguano. The nesting season is long, beginning in late February but some nests are not started until May or even later. Threeeggs are laid. Their chicks hatch withoutdown 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 inbenthic 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.[13][14][15][16] Evidence collected at one colony, theIsle of May, Scotland, between 1985 and 2014, suggests that shag chick diet composition in this population has diversified in response toocean warming.[17] Shags also feed on fewer sandeel on windy days, presumably due to the strong effect of wind on flight in this species.[18] 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.[19]
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 andIsles of Scilly, England;Isle of May,Deerness andFowlsheugh, Scotland;Runde, Norway;Iceland;Denmark;Faroe Islands;Galicia, Northern Spain;Dalmatia andIstria, Croatia. In April 2017, eight new European shags were born inMonaco.[20]
The British population was 18,000 pairs in 2015.[21] The largest colony of European shags is in theCíes Islands, Spain, with 2,500 pairs.[citation needed]
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