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White terns. Birds of the world -17

White tern with fish. Courtesy of Duncan Wright who has placed it in the public domain.

Introduction

In this series we review the birds of the world that occur in a particular genus. These birds occur all over the globe and vary in size and form from the tiniest wren to the largest Ostrich. here in part 17 we review the white terns of the genus Gygis  a genus that contains just one species Gygis alba,while the Little tern is usually considered to be a sub-species of the White tern. The Little tern, Gygis alba macrorhyncha, was first described in 1786 by the Swedish naturalist Anders Erikson Sparrman.

These are small white terns  breeding in the tropical oceans. They nest on coral islands usually in trees with branches,but may also utilize rocky ledges or even man-made structures. The white tern is sometimes referred to as the Fairy tern. They are widespread sea birds which inhabit the islands in the tropical and sub-tropical waters of the south Atlantic ocean, Indian ocean and the western central Pacific. 

The Common white tern, Gygis alba. Description and lifestyle.

This is a most delicate dainty species with a slender body and long tapering wings,a deeply forked tail and black bill,which is unique among terns in that it curves slightly upwards and tapers to a sharp point.The legs are blackish with yellow webs between the toes while the small eyes are surrounded by black rings making them appear much larger than they actually are.

The tern flies with deep slow wing beats in an undulating manner,which although  appears erratic, is extremely strong and even allows for sustained periods of hovering.

Diet--- They forage over deep ocean waters. The Common white tern is a proficient predator of fish,which is its main prey,as well as crustaceans and squid. It spots its prey as it hovers in the wind before diving headlong into the water and seizing its target in its bill. It may also take flying fish in the air,and is commonly seen flying and foraging around groups of Dolphins and predatory fish which drive its prey towards the surface. 

Egg of the White tern on tree cavity. Hawaii.

Courtesy of Forest and Kim Starr.   CC BY-SA 3.0 License.

Breeding habits of the White tern

While solitary for much of the year, during the breeding season the common white tern returns to its nesting colony and forms breeding pairs. The courtship ritual is an elaborate display. the male will ascend to great heights and is followed by the female. Both birds then glide and zigzag their way down. Once on the ground they strut together with tails raised and the wings drooped.

After mating has occurred a single egg is deposited by the female on a depression of a bare branch or in the fork of a tree, unlike other terns, this species does not build a 'nest'. The site is vigorously defended from other birds and intruders which are viciously repelled by bill grabbing and jabbing.

The incubation is carried out by both of the parents,and soon after hatching the chicks, which have well developed feet,toes and claws,start exploring the surrounding area. After fledging the young birds tend to stay with their parents to be fed and they learn from them how to catch their prey before coming fully independent.

The species is threatened by predation from rats and cats which have been introduced to some islands upon which they breed. As a result of this threat some populations have declined. However, the common white tern has benefited on some remote islands  in areas  from human populations. Here the introduction of trees and building construction has increased the amount of breeding habitat available to the species.

The adaptabilty of this species has allowed it to recover from past declines as it can feed on a variety of food types and reproduce quickly. 

Fairy {white} tern feeding chick 

Courtesy of Brocken Inaglory.   CC BY-SA 3.0 license.

Protected areas.

The species is found in a number of protected areas and it also occupies a number of reserves in the Seychelles,while most of its colonies within the Hawaiian archipelago are protected by Nature Reserves. It has also benefited from conservation efforts to remove invasive predators on at least three islands. The population is estimated at between 160,000 and 1,100,000 birds globally and there are no current conservation concerns.

There are three subspecies. The nominate race Gygis alba alba, Gygis alba leucops and the pacific white tern Gygis alba candida. 

Gygis alba alab is found in the tropical islands of the south Atlantic.

Gygis alba candida, is found in the Seychelles and Mascarere islands to central Pacific.

Gygis alba leucops,is found in the Pitcairn islands. 

White terns, Midway Atoll hawaii.

Courtesy of Forest and Kim Starr   CC BY-SA 3.0 License.

The Little White tern. Gygis alba microrhyncha

The little white tern as previously mentioned is generally regarded as a subspecies of the white tern however, some authorities have it has a species in its own right. it is found in French Polynesia and Kiribati.

Fairy tern chick. Courtesy of Amir Balaban. Standard YuoTube License.

Associated pages. Click on the relevant content banner at the top of this page and scroll down to view.

Birds of the world 1-   Larks featuring the Hoopoe Lark.

Birds/world-2             Fulvettas.

Birds/world-3             Rock partridges {Alectoris} 

Birds/world-4             Blue pigeons and two species of Tyrant flycatchers.

Birds/world-5             King parrots.

Birds world-6              Estrilidid Finches. 

Birds/world-7             Grasswrens of Australia.

Birds/world-8            Trogons.

Birds/world-9             Five American Titmice.

Birds/world-10          Cisticola genus.

Birds/world-11          Cuckoos of the genus Clamator.

Birds/world-12          Roadrunners.

Birds/world-13          Black Drongo

Birds/world-14         Green Kingfishers.

Birds/world-15         Tailor birds.

Birds/world-16         Barbets.

All other birds that feature on this site can be found grouped together in the content banners at the top of the page.Click and scroll down to view.

Birds via Links. Click on the Links banner at the top of the page. Scroll down to relevant box. Click this is a direct link to the article {many with videos}

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