Kerguelen Tern
Sterna virgata

Charadriiformes Order – Laridae Family

The Kerguelen Tern occurs only on four islands in the Indian Ocean, and has very restricted range. This species is one of the rarest terns in the world.
Very similar to the Antarctic Tern (S. vittata), which is present in the same range, the Kerguelen Tern has darker plumage and the species can be differentiated in the field by the greyish underwing (white in S. vittata).
The Kerguelen Tern defends aggressively it nest, including eggs and/or chicks, against larger seabirds and even humans.

Length: 33 cm
Wingspan: 71 cm

The Kerguelen Tern adult has smoky-grey upperparts, including the uppertail-coverts, whereas the rump is white. The tail is greyish with grey outer streamers.
The underparts are smoky-grey too, but the undertail-coverts are mostly white. The underwing is grey with narrow, black trailing edge on the primaries.
On the head, forehead, crown and nape are black. Cheeks and moustachial area are white and contrast strongly with the black above, and the grey of chin and throat below.
The bill is deep red. The eyes are dark brown. Legs and webbed feet are bright orange (Crozet) and dull red (Kerguelen).

The non-breeding adult has dull reddish bill (Crozet) or black (Kerguelen). The forehead becomes white by February while the bird is moulting during the incubation.
The juvenile is finely vermiculated grey, brown and buff, with broad pale and dark bars. It is similar to the juvenile S. vittata.

The Kerguelen Tern has two subspecies.
S.v. mercuri occurs on Prince Edward and Marion islands, and on Crozet islands. This race has more restricted grey area on forehead in non-breeder birds, and some subtle differences on the bare parts.
S.v. virgata (described above) is found on Kerguelen Islands.

The Kerguelen Tern is not exclusively marine, and also frequents inland freshwaters. It can be found near ponds, marshes and beaches of all islands.
It breeds on flat ground with sparse vegetation on rocky or volcanic islands, on cliff tops, near rivers and sometimes close to beach.
The non-breeding birds feed in the vicinity of the islands.

The Kerguelen Tern utters high-pitched screams. While foraging, it produces churrs and squeaks.

The Kerguelen Tern feeds on both aquatic and terrestrial invertebrates, according to the season. At sea, it feeds on fish, crustaceans and molluscs caught by plunge-diving and contact-dipping. They forage in flocks of up to 20 birds on inshore waters or by walking on kelp.
On land, it feeds on earthworms, insects and spiders found in the vegetation, taken both on the ground and in flight. Flocks may contain up to 50 individuals. They can be aggressive towards each other while feeding, displacing another by flying towards it while churring.

Kerguelen Tern and Antarctic Tern are probably competing on their breeding islands, and coexistence of these closely related species has involved a parallel reduction of clutch size and the displacement of the laying period. Competition for the limited food resources is reduced and allows both species to feed the chicks. (Weimerskirch & Stahl – 1988)

The Kerguelen Tern is colonial nester and breeds two months before the Antarctic Tern. The colonies include up to 30 pairs, but some of them breed solitary. The nests are widely scattered, about 35-38 metres apart.
The displays are similar to that of S. vittata, and include aerial displays and courtship feeding by male to female. They are generally monogamous.

The Kerguelen Tern is sedentary and remains all year round in vicinity of the breeding islands.
The flight is fast and graceful.  

The laying occurs between mid-October and January, with peak in early November to mid-December.
The nest is placed on the ground, often on slopes above the beach or near the high tide line, occasionally well inland. It is a scrape made with stones and twigs, and lined with plant material such as moss and grass.

The female lays 1-2 eggs and both adults incubate during 24 days. The chicks are brooded for five days. Then, they leave the nest but they hide in vegetation and rocks near the nest. They fledge 31-39 days after hatching, but they still depend on adults for food for about 3 weeks.

The Kerguelen Tern has reduced range and small population. The main threat probably comes from hard weather conditions and strong winds that reduce the food sources and the breeding success.
Predation by skuas still occurs on the islands, but exotic predators have been eradicated from the islands, except a large population of feral cats on Kerguelen.
The global population is estimated at 3,500/6,500 individuals, equivalent to 2,300/4,300 mature individuals. This population appears to be stable.
But currently, the Kerguelen Tern is classified as Near Threatened

Fr: Sterne de Kerguelen
Ang: Kerguelen Tern
All: Kerguelenseeschwalbe
Esp: Charrán de las Kerguelen
Ita: Sterna di Kerguelen
Nd: Kerguelenstern
Sd: Kerguelentärna

Text by Nicole Bouglouan

Sources :

HANDBOOK OF THE BIRDS OF THE WORLD Vol 3 by Josep del Hoyo-Andrew Elliott-Jordi Sargatal - Lynx Edicions - ISBN : 8487334202

A Complete Guide to Antarctic Wildlife by Hadoram Shirihai and Illustrated by Brett Jarrett - Edited by Guy M. Kirwan - ALUL.A Press Oy, Finland - ISBN 9519894705

Avibase (Denis Lepage)

BirdLife International

HBW Alive


Iles Kerguelen


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