The Socotra Cormorant is a medium-large, almost wholly blackish seabird restricted to the waters of the Arabian Gulf, the Gulf of Oman and adjoining seas. Despite its name, its main strongholds lie on islands around the Gulf rather than on Socotra itself. It is a highly social species that breeds and feeds in dense flocks, and colonies can number in the tens of thousands of pairs, forming some of the most concentrated seabird gatherings in the region.
Once extremely abundant, the species has declined markedly since the 1980s as breeding islands have been disturbed, developed or lost, and it is now classed as Vulnerable. Its fortunes are tied closely to the small shoaling fish of the Gulf and to the handful of undisturbed islands where it can raise young, which makes it sensitive to coastal development, oil pollution and human disturbance.
The Socotra Cormorant is a slim, long-bodied cormorant that looks almost entirely black at a distance. In breeding condition it shows a subtle purplish gloss on the forecrown and a slaty-green sheen on the upperparts, with a scattering of fine white plumes around the eye and neck and a few white streaks on the rump. The bill, legs and gular skin are all dark.
| Size | Medium-large cormorant, about 80 cm long |
| Plumage | Almost entirely blackish, with a green-and-purple sheen when breeding |
| Breeding marks | A few fine white plumes near the eye and neck and white streaks on the rump |
| Bill | Long, dark and hook-tipped |
| Bare parts | Black legs, feet and gular (throat) skin |
| Behaviour | Highly gregarious; feeds and roosts in dense flocks |
Like other cormorants, the Socotra Cormorant is generally silent away from the colony but noisy when breeding. At the nest birds give low guttural grunts, croaks and growling calls during displays and squabbles over sites. In a large colony these calls combine into a constant low murmur beneath the movement of thousands of birds.
The species is a regional endemic of the Arabian Gulf, the Gulf of Oman and neighbouring waters, with breeding islands off the United Arab Emirates, along the Gulf and in the Gulf of Oman. It is a marine bird that forages over inshore and offshore waters and comes to land chiefly on low, sparsely vegetated islands where it nests and roosts in huge numbers.
Socotra Cormorants are pursuit-diving piscivores that feed on small shoaling fish, including sardines, scads, silversides, halfbeaks and rabbitfishes. Large flocks often forage together, diving from the surface to chase fish underwater, and feeding aggregations may attract other seabirds. Their reliance on Gulf forage fish links their breeding success closely to local fish abundance.
Breeding takes place in dense ground colonies on flat, open islands, where nests are simple scrapes or low mounds packed close together. The clutch is usually two to three eggs, incubated for around 24 to 27 days, and both parents share incubation and feeding of the chicks. The tightly grouped nesting makes colonies highly sensitive to disturbance, which can cause widespread breeding failure.
- Great Cormorant: Larger and bulkier, with white on the face and thigh; overlaps in Gulf waters in winter
- Pygmy Cormorant: Much smaller cormorant of the wider region with a shorter bill and browner tone
- Socotra Shag: Slimmer dark cormorant relatives (shags) are similarly glossy but have crests and different ranges
Does the Socotra Cormorant live on Socotra?
Only partly. Despite the name, its main breeding colonies are on islands in the Arabian Gulf and Gulf of Oman rather than on Socotra itself.
Why is it Vulnerable?
Its population has declined since the 1980s because breeding islands have been disturbed and developed, and the species is exposed to oil pollution and loss of nesting sites.
How large are its colonies?
Breeding colonies can hold tens of thousands of pairs packed densely together, among the largest seabird concentrations in the region.
What does it eat?
It feeds mainly on small shoaling fish such as sardines, scads and silversides, caught by diving from the surface.