White Tern

## Description

The white tern or common white tern (Gygis alba ) is a small seabird found across the tropical oceans of the world. It is sometimes known as the fairy tern although this name is potentially confusing as it is also the common name of Sternula nereis. Other names for the species include angel tern and white noddy in English, and manu-o-Kū in Hawaiian. The little white tern (Gygis microrhyncha ), previously considered a subspecies of the white tern (Gygis alba microrhyncha ), is now recognised as a separate species.

## Appearance

The White tern is a very elegant and delicate seabird, with immaculate all-white plumage. The small eyes surrounded by black rings make them seem much larger. Adults look the same, but juveniles have a brownish-gray back and gray on their neck, with a black mark behind their eyes. These dainty terns fly in an undulating pattern with deep, slow wingbeats, which, although it appears erratic, is very strong and enables sustained periods of hovering.

## Distribution

White terns breed in subtropical and tropical South Atlantic, Pacific, and Indian Oceans. They are pelagic birds that live in oceanic areas, relatively close to coral breeding islands with some vegetation, where they will nest in bushes and trees, foraging over deep ocean waters.

## Behavior

White terns are often seen on their own or in small groups. They are a diurnal species but are more active at dawn and dusk. To eat, it dips its beak to catch prey at the water’s surface or just beneath it. A dive is often preceded by extensive hovering, and the bird may use the wind to sustain its flight. It may catch flying fish from the air, and it is commonly seen foraging near groups of predatory fish and dolphins which drive their prey towards the surface. An individual may carry a few small fish in its bill, taking these to its young with the prey held crosswise. If disturbed by a predator, a White tern will hover, flutter and make buzzing sounds. This bird has a graceful flight. It flies easily low above the waves, without landing. It will touch the surface once it has spotted prey. Its flight is buoyant, involving erratic changes in speed and direction.

## Diet

White terns are carnivores (piscivores). They mainly eat small fish and squid, and sometimes crustaceans.

## Reproduction

White terns are monogamous and pairs remain with each other for several seasons, returning every year to the same nesting site. These birds nest in loose groups or singly. They can breed at any time during the year, but there are peaks from late spring until early summer. At the start of the breeding season, pairs engage in aerial displays, flying with each other. They probably do courtship feeding, with the male giving some prey to his mate, and mutual preening while perched on a branch. These birds do not build a nest. Sometimes they will scratch the bark of a short branch high in a tree, to make a small shallow depression, using their feet and bill to do so. The egg is sometimes laid on a roof or other surface, but always on a bare surface. One speckled egg is laid and incubation is for about 36 days, by both parents. The chick is brooded in its branch nest. Both parents feed their chick every 3 hours, bringing small fish or squid. The young fledges at around 48 days of age when it moves into the area surrounding the nest site. It returns to the nest branch only for feeding. Both parents feed it for 2 more months. Young White tern usually reach reproductive maturity at around 3 to 5 years of age.

## Population

### Population threats

Although currently not at risk of extinction, White terns are threatened by predation from cats and rats, introduced onto some of their breeding islands. This has caused some populations to decline and others have disappeared.

### Population number

According to IUCN Red List, the total population size of the White tern is 150,000-1,100,000 individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today remain stable.

## Fun Facts for Kids

White terns make a repeated guttural “heech-heech”. At the nest site, they are usually silent.

White terns were first described by Anders Erikson Sparrman, in 1786, a Swedish naturalist.

A group of terns is called a "U" of terns or a "ternery".

A White tern will often lay its egg straight onto a bare branch without a nest to support it.

It is difficult for an egg to be balanced on a branch. A strong wind could blow it off if the parent bird is not sitting on it. The parents must change places very carefully to avoid knocking the egg off.

Once it hatches, a tern chick tightly grips the branch. Its strong feet and claws on hatching enable it to balance on a branch better than an egg can, though a strong wind is still a problem.

White terns are also called “fairy terns” due to their delicate features and their zipping, "skipping," and hovering overhead.