Common white tern (Gygis alba)

Also known as: angel tern, common fairy tern, common white-tern, fairy tern, white noddy, white tern
  
French: Gygis blanche
KingdomAnimalia
PhylumChordata
ClassAves
OrderCharadriiformes
FamilyLaridae
GenusGygis (1)
SizeHead-body length: 25 – 30 cm (2)
Wingspan: 76 – 80 cm (2)
Weight92 – 139 g (2)

Classified as Least Concern (LC) on the IUCN Red List (1).

Perhaps the most elegant and delicate seabird, the common white tern, also known as the fairy or white tern, has immaculate all-white plumage (2). This dainty bird has a slender body with long, tapering wings, a short, deeply forked tail and a black bill, which is unique amongst terns in that it curves slightly upwards and tapers to a sharp point (2) (3) (4). The legs are blackish with yellow webs between the toes, while the small eyes are surrounded by black rings making them appear much larger (2) (3). Adult common white terns look alike, but the juvenile has a brownish-grey back with grey on the neck and a black mark behind the eye. This tern flies with deep, slow wingbeats in an undulating pattern, which, although appearing erratic, is extremely strong and even allows for sustained periods of hovering (2) (4).

A widespread seabird, the common white tern inhabits islands in the tropical and subtropical waters of the south Atlantic Ocean, Indian Ocean and western and central Pacific (3) (5).

The common white tern breeds on small islands made of coral with some degree of vegetation, where it nests in trees and bushes, and forages over deep ocean waters (2) (3) (5).

The common white tern is a proficient predator of fish, which is its main prey, as well as crustaceans and squid (2). It spots its prey as it hovers in the wind before diving headlong into the water and seizing its target in its bill (4). It may also take flying fish in the air and is commonly seen foraging around groups of dolphins and predatory fish which drive its prey towards the surface (3). 

While solitary for much of the year, during the breeding season the monogamous common white tern returns to nesting colonies and form breeding pairs (3). Breeding birds engage in elaborate courtship displays where the male ascends at speed to great heights, followed by the female. The pair then glide and zigzag downwards before strutting together on the ground with the tail raised and the wings dropped (4). After mating, a single egg is laid on a depression of a bare branch as, unlike other terns, this species does not build a nest (3) (5). This nest site is aggressively defended from other birds, and intruders are viciously repelled by bill grappling and jabbing (3). Both the male and female share the incubation duties and soon after hatching, the chicks, which have well developed feet, toes and claws, start exploring the surrounding area (3) (4). After fledging, the young birds stay with the parents to be fed and learn how to catch prey before becoming fully independent (4). 

Although not currently at risk of extinction, the common white tern is threatened by predation from rats and cats, which have been introduced onto some islands upon which it breeds. As a result of this threat, some populations have declined while others have been lost completely. However, the common white tern has benefited on some remote islands areas from human occupation, such as on Midway Aoll where the introduction of trees and building construction increased the amount of nesting habitat available to the species. Similarly, a breeding population was established on Tern Island after the island’s vegetation was altered and buildings were constructed. The adaptable nature of this species has also allowed it to recover from past declines as it can feed on a variety of food types and reproduce quickly (3).    

The common white tern is not currently the target of any specific conservation measures, but it is found in a number of protected areas. It occupies a number of reserves in the Seychelles, while most of its colonies within the Hawaiian archipelago are protected by national reserves (3). It has also benefited from conservation efforts to remove invasive predators on Rose, Kure and Midway Atolls and Pitcairn Island (3) (6).  

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  1. IUCN Red List (July, 2010)
    http://www.iucnredlist.org/
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (2001) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
  3. Niethammer, K.R. and Patrick. L.B. (1998) White Tern (Gygis alba). Cornell Lab of Ornithology. The Birds of North America Online.
  4. Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
  5. BirdLife International (July, 2010)
    http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3298&m=0
  6. Procter, D. and Fleming, L.V (1999) Biodiversity: the UK Overseas Territories. Joint Nature Conservation Committee, Peterborough, UK. Available at:
    http://www.jncc.gov.uk/page-3045%23download