Socotra Cormorant Phalacrocorax nigrogularis Scientific name definitions

76–84 cm; wingspan 102–110 cm. Noticeably slim, long-billed cormorant with short tail and no crest. Breeding adult  black with purplish to oily green gloss, conspicuous white tuft of long white filoplumes on ear-coverts, some sparse, long white filoplumes usually concentrated on lower back to rump, rear flanks and rear of thighs; feathers of mantle, scapulars and upperwing have small black spot at tip and otherwise more oily, with slight bronze to olive gloss visible at close range, the bird looking all black at distance; underwing black over most coverts forming black band on most of leading edge, contrasting with grey bloom to greater coverts and remiges; later during breeding season white filoplumes are lost, often has narrow, paler gular band outlining the pouch; in non-breeding season is slightly duller black, neck may have tiny white specks, white filoplumes number just a few on neck; iris green; naked skin on lores and around eye and gular pouch blackish, the former with radial pattern of paler lines visible at a very close range; bill blackish grey with greenish-yellow line along basal half of mandible, may be partially horn-coloured out of breeding season; legs greyish black. Sexes similar, but male averages larger. Juvenile brownish grey to earth brown over head, neck, upperparts and thighs, often darker on scapulars and upperwing-coverts (darkest on greater coverts), which are pointed and fringed whitish drab, the upperwing secondary-coverts may appear as pale panel when wing is spread, primary-coverts and remiges blackish brown, tail blackish with pale shafts, brownish white on throat , foreneck and, most noticeably, on lower foreneck to abdomen, flanks grey-brown, iris grey initially, soon becoming green, facial skin, gular pouch and bill flesh-grey to flesh-pink or more usually horn-yellow, usually with dusky culmen, legs grey with some dull pinkish to flesh-brown tinge; subsequent plumage darker and browner, rather spotted at close range, and underparts less whitish. Large, slim cormorant unlikely to be confused except in juvenile plumage, which looks very like that of Gulosus aristotelis desmarestii, from which separated by being larger on average and, especially, by flesh to pinkish  rather than yellowish gular skin, and throat is often browner, less white, but this is variable.

Two subpopulations: in N breeding on Persian Gulf islands off coasts of Saudi Arabia, Bahrain, Qatar and United Arab Emirates, possibly also still off Iran (breeding not confirmed since 1972); S subpopulation breeds on one or more islands in Arabian Sea off Oman and in Gulf of Aden off S Yemen, and confirmed recently also at Socotra. Recently found to occur in Red Sea and reported possible breeding on islands off Eritrea (1 Semere, D., Hagos, T., Seleba, G., Gebrezgabhier, Y., Haile, Z., Chiozzi, G. and De Marchi, G. (2008). The status of breeding seabirds and waterbirds on the Eritrean Red Sea islands. Bull. Afr. Bird Club 15(2): 228–237. Close ). Somewhat more widespread in non-breeding season.

Exclusively marine , even to extent of preferring not to fly over land. Breeds on small desert islands. Rests on sandbanks, coastal cliffs and islets.

Migratory or dispersive; poorly known. Disperses over Persian Gulf and Arabian Sea, where occurs year-round, reaching Gulf of Aden; vagrant to Red Sea coasts of E Africa N to Eritrea, and also off W India. Also performs some movements connected with feeding; moves in flocks, sometimes enormous, this sometimes interpreted as migration.

Probably mainly fish , particularly small shoaling fish. Prey species poorly known, probably include sardines (Sardinella), scads (Selar crumenophthalmus and Atule mate), silverside (Atherinomorphus lacunosus), spotted half-beak (Hemiramphus far) and streaked rabbit-fish (Siganus javus) (2 King, H. (2004). Communal behaviour of Socotra cormorant, Bahrain. Phoenix. 20: 25-28. Close ). Feeds mainly by pursuit-diving; reaching depths of 18 m or more (2 King, H. (2004). Communal behaviour of Socotra cormorant, Bahrain. Phoenix. 20: 25-28. Close ). Forms offshore feeding flocks, sometimes immense, which can detect prey from air, and which fish collectively, but thought to be communal forager, rather than co-operative one (3 Nelson, J. B. (2005). Pelicans, Cormorants and their relatives. Pelecanidae, Sulidae, Phalacrocoracidae, Anhingidae, Fregatidae, Phaethontidae. Oxford University Press, New York. Close ).

Little information.

Season very variable, with breeding recorded in most months, but each colony is synchronized internally. Breeding reported Jun–Oct at Indian Ocean colonies but those in Gulf active in Sept–Apr, when conditions are cooler and prey availability reaches maximum (4 Wilson, K. D. P. (2012). Breeding of Socotra Cormorant at Umm Qasar Island, UAE. Phoenix. 28: 26–28. Close ). Forms dense colonies, sometimes of tens of thousands of pairs. Nest a scrape in gravel or sand, or in slightly raised mound. Clutch 2–4 eggs; no information on incubation period; chicks naked  , grow white down, and gather in groups or crèches as soon as they can move about. Plantations of Acacia spp. and Prosopis juliflora on Siniya I (off Umm Al Quwain), N United Arab Emirates, appear to benefit the colony there: egg volumes and hatching success were higher under shaded areas and chicks crèched under the trees soon after leaving their nests (5 Bin Muzaffar, S., Gubiani, R. and Benjamin, S. (2012). Reproductive Performance of the Socotra Cormorant Phalacrocorax nigrogularis on Siniya Island, United Arab Emirates: Planted Trees Increase Hatching Success. Waterbirds. 35(4): 626–630. Close ). During a study on Siniya I, in Oct–Dec 2011, older (fledged) chicks were observed to consume younger (altricial) chicks, possibly as a consequence of forced starvation caused by abandonment by parents, frequency of such cannibalistic events suggesting that behaviour perhaps not uncommon for this species (6 Gubiani, R., Benjamin, S. and Bin Muzaffar, S. (2012). First Record of Cannibalism in Socotra Cormorants (Phalacrocorax nigrogularis): Large, Immature Birds Opportunistically Feed on Younger Conspecifics. Waterbirds. 35(2): 338-341. Close ).

VULNERABLE. CITES II. Has small global range within which it is thought to be in rapid decline. Estimated total breeding population c. 110,000 pairs. According to BirdLife International, species has very small area of occupancy within its limited breeding range, with only 13 colonies currently known to be active (nine general locations); three largest contain at least 75% of world population, that on island of Suwad al Janubiyah (in Hawar archipelago), off W Qatar, the largest. Breeding confirmed for first time at Socotra in Mar 2005, when colony of c. 500 individuals found on islet of Saboniya, and population now known to number c. 6250 pairs. Recently found to occur throughout year on Red Sea coast of Eritrea, where reported by local inhabitants as breeding in late summer (7 Semere, D., Hagos, T., Seleba, G., Gebrezgabhier, Y., Haile, Z., Chiozzi, G. and De Marchi, G. (2008). The status of breeding seabirds and waterbirds on the Eritrean Red Sea islands. Bull. Afr. Bird Club. 15(2): 228–237. Close ). In N subpopulation, c. 12 colonies have become extinct since 1960s, representing potential decline of up to c. 80,000 pairs (at least a quarter of N subpopulation); in Saudi Arabia, number of breeding pairs declined by more than 75% during 1980–1992. Declines believed to be continuing as result of coastal development, disturbance and marine pollution. Coastal development at breeding sites probably main threat, as colonies, once displaced, probably unable to establish themselves elsewhere; also, human disturbance at breeding sites is frequent, and permits extensive predation of eggs by large gulls (Larus). Extinction of colonies in N since 1960s attributed to encroachment by development and prolonged human disturbance. Highly vulnerable to marine oil spills: for example, in Aug 1980, a spill of c. 20,000 barrels of light crude oil off Bahrain coast killed up to 1000 birds, most of them the present species. Several spills related to armed conflicts in region, e.g. major spill in early 1991 reckoned to have killed minimum of 25,000–30,000 seabirds, most of them grebes (Podicipedidae) and cormorants, with present species most affected of all, accounting for 37% of 1350–1500 birds attended in recovery centre; thought to have killed 20% or more of Saudia Arabian population of this cormorant (8 Symens, P. and Suhaibani, A. (1993). Impact of Gulf War oil spills on wintering seabird populations along the northern Arabian Gulf coast of Saudi Arabia, 1991. Sandgrouse. 15: 37-43. Close ); slick was carried S by water current, but held up at Abu’ Ali I (E Saudi Arabia) and prevented from reaching Bahrain and major breeding colonies at Zakhnuniyah and on Huwar Is; 15,000 counted in Oman in Jan 1991, outside immediate zone of conflict. In addition to direct mortality, reduced immune function and reduced breeding success caused by oiling and oil-ingestion, spills deplete fish stocks. Being a piscivore, this species is susceptible also to other marine pollutants such as heavy metals and PCBs (polychlorinated biphenyls), as well as neurotoxins. Other potential threats posed by fisheries (depletion of food stocks), introduced predators on breeding islands, harvesting of chicks and eggs for food, and direct persecution; also, this cormorant is regularly found drowned in fishing traps. A ground-nesting species, it is susceptible to effects of storms, e.g. flooding of nests during heavy rains (as occurred on Suwad al Janubiyah in Nov 1997) and sudden mass abandonment of chicks (as on Suwad in Apr 2003 owing to isolated thunderstorm with strong winds). Legally protected in most of range, but not in United Arab Emirates . Research on this species has increased since end of 20th century, and some conservation measures, including protection of breeding sites, have been introduced.