Gull-billed Tern.
Photo: Purnell Collection © Australian Museum
Distribution map of Sterna nilotica
Map © Birds Australia Birdata
Gull-billed Tern
Scientific name: Sterna nilotica
Family: Laridae
Order: Charadriiformes
- Featured Bird Groups
- Sea birds
What does it look like?
Description
The Gull-billed Tern is entirely white, except for a black crown from bill to nape, a grey back and upper wings and darker flight feathers. The iris is dark brown, bill and legs black. The sexes are similar. In non-breeding plumage, the head is mainly white, the crown streaked brownish-grey and the ear coverts are dull black. Immature birds are similar to non-breeding adults. Juveniles are similar to immature birds, but the shoulders are mottled grey and brown. The common name relates to the thicker, shorter bill of this tern, closer in shape to that of a gull.
Similar species
Gull-billed Terns resemble Crested Terns, S. bergii, and Silver Gulls, Larus novaehollandiae, but the short stout black gull-like bill, black head with no crest and long legs are diagnostic.
Where does it live?
Distribution
The Gull-billed Tern occurs on all continents except Antarctica.
Habitat
Gull-billed Terns are found in freshwater swamps, brackish and salt lakes, beaches and estuarine mudflats, floodwaters, sewage farms, irrigated croplands and grasslands. They are only rarely found over the ocean.Seasonal movements
The Gull-billed Tern is nomadic or migratory. Although essentially an inland species, outside breeding season it shows a distinct preference for saltmarshes and lagoons near the coast. Movements are not fully understood but it is common and widespread in south-eastern Australia, and only a vagrant in Tasmania. It winters mainly in the north and substantial numbers migrate to New Guinea and perhaps Indonesia.What does it do?
Feeding
The diet of the Gull-billed Tern is extremely varied, consisting mainly of small fish, reptiles, amphibians, crustaceans, small mammals, insects and their larvae. When fishing, the Gull-billed Tern fans out its tail and with wings outstretched and flapping occasionally, glides swiftly down to the surface of the water. It tilts its head downwards so that its bill is nearly vertical and only the tip touches the water. After seizing its prey the bird gains height rapidly and continues its slow hawk-like flight. It does not dive or settle on the water.
Breeding
The breeding season of the Gull-billed Tern is flexible, depending on location. Generally the terns choose to nest in colonies on high, dry ground on small permanent or temporary islands in a lake or marsh. There are few breeding reports north of about 25° S. The nests are shallow depressions scraped in sand or mud, lined with some vegetation. Both sexes incubate the eggs.References
Pringle, J.D. 1987. The Shorebirds of Australia. Angus and Robertson and the National Photographic Index of Australian Wildlife, Sydney.
Schodde, R. and Tideman, S.C. (eds) 1990. Reader's Digest Complete Book of Australian Birds (2nd Edition). Reader's Digest (Australia) Pty Ltd, Sydney.
Morcombe, M. 2000. Field guide to Australian Birds. Steve Parish Publishing.
Simpson, K and Day, N. 1999. Field guide to the birds of Australia, 6th Edition. Penguin Books, Australia.