This large tern is closely related to other species in its genus, but can be distinguished by its darker, battleship-grey upperparts, white forehead even in full breeding plumage, and greenish-tinged yellow (not orange or black) bill colour.

Its young have a distinctive appearance, with strongly patterned grey, brown and white plumage, and rely on their parents for food for several months after they have fledged.

This is an adaptable species that has learned to follow fishing boats for jettisoned bycatch, and to use unusual nest sites such as the roofs of buildings and artificial islands in salt pans and sewage works.

They are gull-like in appearance, but typically have a lighter build, long pointed wings (which give them a fast, buoyant flight), a deeply forked tail and short legs.

[10] The greater crested tern has four or five geographical subspecies (depending on authority), differing mainly in the darkness of the upperparts and the bill dimensions.

In winter, the upperparts plumage wears to a paler grey, and the crown of the head becomes white, merging at the rear into a peppered black crest and mask.

For T. b. cristatus, the moult timing depends on location; birds from Australia and Oceania are in breeding plumage from September to about April, but those in Thailand, China and Sulawesi have this appearance from February to June or July.

[13] The royal tern is similar in size to this species, but has a heavier build, broader wings, a paler back and a blunter, more orange bill.

[16] The greater crested tern occurs in tropical and warm temperate coastal parts of the Old World from South Africa around the Indian Ocean to the Pacific and Australia.

The subspecies T. b. bergii (including the doubtfully distinct T. b. enigma) breeds in southern Africa from Namibia to Tanzania, and possibly on islands around Madagascar.

There is then a break in the breeding distribution of the species until T. b. velox is met in Somalia, the Red Sea, and the Persian Gulf, and another discontinuity further east in southern India.

[16] When not breeding, the greater crested tern will roost or rest on open shores, less often on boats, pilings, harbour buildings and raised salt mounds in lagoons.

When Southern African birds leave colonies in Namibia and Western Cape Province, most adults move east to the Indian Ocean coastline of South Africa.

Since nesting in this area follows the summer monsoonal flooding, it is presumably a response to fish stocks rising, probably due to river run-off providing extra nutrient to the Gulf.

[14] In South Africa, this species has adapted to breeding on the roofs of building, sometimes with Hartlaub's gull, which also shares the more typical nesting sites of the nominate subspecies.

Juvenile survival rates are improved where trawler discards provide extra food, and huge population increases in the southeastern Gulf of Carpentaria are thought to have been due to the development of a large prawn trawl fishery.

[14] An unusual incident was the incapacitation of 103 terns off Robben Island, South Africa by marine foam, generated by a combination of wave action, kelp mucilage and phytoplankton.

[34] Fish are the main food of the greater crested tern, found to make up nearly 90% of all prey items with the remainder including cephalopods, crustaceans and insects.

[33] The greater crested tern feeds mostly at sea by plunge diving to a depth of up to 1 m (3.3 ft), or by dipping from the surface, and food is usually swallowed in mid-air.

The plan is intended to address key issues such as species and habitat conservation, management of human activities, research, education, and implementation.