The sooty tern (Onychoprion fuscatus) is a seabird in the family Laridae. It is a bird of the tropical oceans, returning to land only to breed on islands throughout the equatorial zone.
Taxonomy
The sooty tern was described by Carl Linnaeus in 1766 as Sterna fuscata, bearing this name for many years until the genus Sterna was split up. It is now known as Onychoprion fuscatus. The genus name is from ancient Greek , "claw" or "nail", and , "saw". The specific fuscatus is Latin for "dark".
Colloquially, it is known as the wideawake tern or just wideawake. This refers to the incessant calls produced by a colony of these birds, as does the Hawaiian name ʻewa ʻewa which roughly means "cacophony". In most of Polynesia its name is manutara or similar – literally "tern-bird", though it might be better rendered in English as "the tern" or "common tern". This refers to the fact that wherever Polynesian seafarers went on their long voyages, they usually would find these birds in astounding numbers. It is also known as kaveka in the Marquesas Islands, where dishes using its eggs are a delicacy.
The sooty tern has little interspecific variation, but it can be divided into at least two allopatric subspecies. Some recent authors further subdivide the Indopacific population into up to eight subspecies altogether, but much of the variation is really clinal. The affinities of eastern Pacific birds (including the famous manutara of Easter Island) are most strongly contested.
Onychoprion fuscatus fuscatus (Linnaeus, 1766) – Atlantic sooty tern
Underparts white. Breeds Atlantic and Caribbean.
Onychoprion fuscatus nubilosus (Sparrman, 1788) – Indopacific sooty tern
Underparts light grey in fresh plumage, dull white in worn plumage. Breeds from Red Sea across Indian Ocean to at least central Pacific. Some authors restrict this taxon to the Indian Ocean population and use the following subspecies for the birds from Indonesia to the Americas: Onychoprion fuscatus infuscatus – Sunda sooty tern (Lichtenstein, 1823) – Sunda Islands and vicinity Onychoprion fuscatus oahuensis – Central Pacific sooty tern (Bloxam, 1826) – Bonin Islands through Micronesia to southern Polynesia Onychoprion fuscatus serrata – Melanesian sooty tern (Wagler, 1830) – Australia, New Guinea, New Caledonia Onychoprion fuscatus luctuosa – Juan Fernández sooty tern (Philippi & Landbeck, 1866) – Juan Fernández Islands Onychoprion fuscatus crissalis – East Pacific sooty tern Lawrence, 1872. – Eastern Pacific from Guadalupe Island to Galápagos Islands Onychoprion fuscatus kermadeci – Kermadec sooty tern Mathews, 1916. – Kermadec Islands Onychoprion fuscatus somaliensis – Somali sooty tern – Maydh Island (Gulf of Aden)
Description
This is a large tern, similar in size to the Sandwich tern (Thalasseus sandvicensis) at long with an wingspan. The wings and deeply forked tail are long, and it has dark black upperparts and white underparts. It has black legs and bill. The average life span is 32 years. Juvenile sooty terns are scaly grey above and below. The sooty tern is unlikely to be confused with any tern apart from the similarly dark-backed but smaller bridled tern (O. anaethetus). It is darker-backed than that species, and has a broader white forehead and no pale neck collar.
The call is a loud piercing or .
Ecology
Sooty terns breed in colonies on rocky or coral islands. It nests in a ground scrape or hole and lays a single egg, typically in the afternoon. Although "two-egg clutches" have been reported, they probably occur when an egg from one nest rolls into another. It feeds by picking fish from the surface in marine environments, often in large flocks, and rarely comes to land except to breed, and can stay out to sea for 3 to 10 years. Due to the lack of oil in its feathers, it cannot float, and spends that entire time on the wing.
This bird is migratory and dispersive, wintering more widely through the tropical oceans. It has very marine habits compared to most terns; sooty terns are generally found inland only after severe storms. The Field Museum, for example, has a male specimen which was found exhausted on August 2, 1933 on the slopes of Mount Cameroon above Buea, about ASL, after foul weather had hit the Gulf of Guinea. This species is a rare vagrant to western Europe, although a bird was present at Cemlyn Bay, Wales for 11 days in July 2005.