Tern (Caspian) Hydroprogne caspia
Species: H. caspia
Binomial name: Hydroprogne caspia
Synonyms: Sterna caspia, Hydroprogne tschegrava, Helopus caspius
Common names: Caspian tern, Taranui
The Caspian tern (Hydroprogne caspia) is a species of tern, with a cosmopolitan but scattered distribution. In New Zealand this native bird lives along a the coasts of both islands.
It is the world's largest tern with a length of >60 cm, a wingspan of >145 cm and a weight of 700 g. It has a massive red bill tipped with black and yellow. Adults have black legs. Their body is a silver-grey above and is white underneath. The white head has a black cap. The underwings are pale with dark primary feathers. In flight, the tail is less forked than other terns.
They feed mainly on fish that they dive for, usually just beyond the shoreline. They hover high over the water and then plunge onto their prey. They often fish on freshwater lakes as well as at sea. They also occasionally eat large insects, the young and eggs of other birds and rodents. They may fly up to 60 km from the breeding colony to catch fish.
Breeding is in spring and summer, with one to three pale blue green eggs, with heavy brown spotting, being laid. They nest either together in colonies, or singly in mixed colonies of other tern and gull species. The nest is on the ground among gravel and sand, or sometimes on vegetation; incubation lasts for 26–28 days. The chicks are variable in plumage pattern, from pale creamy to darker grey-brown; this variation assists adults in recognizing their own chicks when returning to the colony from feeding trips. Fledging occurs after 35–45 days.
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