White Tern
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White Tern

Common name: White Tern
Scientific name: Gygis alba
Length: 31 cm
Weight:
Population: abundant
Distribution: tropical islands in the Pacific and Indian oceans
Issue: invasive species
IUCN Red List status: least concern

Description:
The White Tern is a small white bird with a black beak that nests in trees on coral islands in the Pacific and Indian Oceans. Males and females are identical in appearance.

The bird’s nesting season varies from place to place. Typically, it begins around March and ends in late August or early September. The species is famous for laying only one egg per season. This egg is laid directly into a hollow or fork of a small branch, and no nest is made. This unusual behaviour probably evolved as a way to avoid nest parasites, which can sometimes cause entire colonies to be abandoned. However, this strategy also makes the egg more vulnerable, especially to the wind. If the egg breaks, the parents will quickly replace it with a new one. For five weeks, the parents take turns incubating the egg and going out to sea to find food. Once the chick hatches, it remains with the parents for three to four months, until it learns to feed itself.

The White Tern feeds primarily on small fish, which it catches by diving into the water. It occasionally takes crustaceans and squid. Most individuals can expect to live for about 17 years, but the oldest known White Tern lived to be 42.

Threats:
The population on the island of Guam nearly went extinct after the introduction of the brown tree snake. The eggs are also vulnerable to other invasive species that wreak havoc with island ecosystems, such as rats. However, the species is widespread enough throughout the world that it has been given a status of least concern on the IUCN Red List.

Did you know?
The White Tern was declared the official bird of Honolulu, the capital of Hawaii. Its Hawaiian name is mnu-o-Kū. Historically, Polynesians observed the flight of the White Tern to orient their explorations. So indirectly, the White Tern helped colonize the islands of the South Pacific.

REFERENCES: Red List of Threatened Species of the International Union for Conservation of Nature (IUCN) and Encyclopedia of Life.

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