Little tern

Sternula albifrons (Pallas, 1764)

Order: Charadriiformes

Family: Sternidae

New Zealand status: Native

Conservation status: Migrant

Geographical variation: There are three subspecies spread through Europe, Africa , Asia and Australia. S. a. sinensis breeds from eastern Asia to Australia and occurs in New Zealand.

Little tern. Non-breeding adult. Clive rivermouth, Hawke's Bay, October 2016. Image © Adam Clarke by Adam Clarke

Little tern. Non-breeding adult. Clive rivermouth, Hawke's Bay, October 2016. Image © Adam Clarke by Adam Clarke

Although small numbers of little terns visit New Zealand every year, it took some time before they were recognised as being New Zealand birds. They are very similar to the now rare fairy tern, especially in the nondescript non-breeding and immature plumages most often seen in New Zealand. Even museum specimens were misidentified and over-looked. Careful observations by Ross McKenzie and Dick Sibson led to the presence of little terns being confirmed on the Miranda coast, Firth of Thames in the 1950s. By this time, the fairy tern had become one of New Zealand’s rarest birds, and the little tern is now known to be the commonest small tern in the country over the summer. Further observations have shown that birds seen in New Zealand come from two different populations; most of them are northern hemisphere migrants that spend their non-breeding season in New Zealand but a few are from the population breeding in Australia and they can be recognised by having a moult cycle that is six months different.

Identification

Little terns are very small, slender terns with a short tail that has a shallow fork. They are pale birds, light grey on the back and upper wings and white on the rump, tail and underparts. The black cap is separated from the bill by an extensive white forehead. Little terns may be distinctive in flight, frequently stopping to hover when they are feeding.

In New Zealand most birds are in non-breeding or immature plumage, with black bills, and white extending from the forehead to the crown. The crown is white variably mottled with black, and a band of black across the rear of the crown reaches to just in front of the eyes. A blackish leading edge to the wing shows as dark shoulder stripe and 2-3 dark primaries when they are at rest. The legs are brownish. In breeding plumage the bill of adults becomes clear yellow with a black tip, and the whitish crown becomes black with stripes extending through the eye to the sides of the bill. The forehead is broadly white, with sharp-ended white wedges reaching back over the eye (cf. fairy tern). The outer feathers of the tail lengthen to reach almost as far as the wing tips. Most little terns in New Zealand are Northern Hemisphere migrants acquiring breeding plumage from February onward.

Voice: the common flight call made by little terns is a sharp “kik” repeated several times. This is sharper than the similar call made by fairy terns. A rapid chatter “chit-chit-chit” may also be given when feeding.

Similar species: fairy terns are very similar to little terns and care is needed to separate them. In all plumages fairy terns are more robust and deep-bellied, with short legs and a bill that is slightly deeper at the base and straight along the top edge. In contrast little terns are slim, longer legged and the bill has a slight curve along the top edge. In fairy tern breeding plumage, the black spot in front of the eye stops well short of the base of the bill. There is a short blunt-ended white stripe over the eye. The yellow bill has a distinctly orange tone and lacks a black tip. In non-breeding plumage, fairy terns develop a black tip to their bills which also become stained to some degree with brown and there is at least a little white flecking in their crowns at this time.

Juvenile fairy terns are very similar to little terns in immature or non-breeding plumage. Apart from differences in shape (see above) the black patch in front of the eye is short but very deep, particularly extending below the level of the eye. Juvenile fairy terns have a dark brownish bill that is never quite black but the bills of little terns become lighter as they enter breeding plumage and may be similar at this time.

Distribution and habitat

Little terns are widespread in Europe, Africa and Asia, with the eastern subspecies, S. a. sinensis, breeding widely from India to Japan to northern and eastern Australia. Birds from Asian populations are trans-equatorial migrants, arriving in New Zealand during October and departing in March, with some younger birds leaving later (sometimes as late as May). Australian birds are short distance migrants or disperse locally within Australia. The few that reach New Zealand arrive from April with adults known to depart in October or November. There have been band recoveries in New Zealand of birds marked in Japan and Australia.

In New Zealand, little terns inhabit sheltered coastal waters, and may occur in estuaries and harbours right around the New Zealand coast. Particularly favoured localities are Manukau, Kaipara and Rangaunu Harbours, where small flocks may occur.  There is a single record from each of Chatham Island (December 1997 to January 1998) and Macauley Island, Kermadec Islands (November 1980).

Population      

Possibly up to 100 little terns may occur in New Zealand each year but occasionally larger numbers occur.

Threats and conservation        

Little terns breeding in Australia are regarded as vulnerable as the population breeding in the south-east is small and has declined due to human disturbance, predation and natural catastrophes. The number of Asian-breeding birds migrating to Australia appears to be stable, and so these populations may not be threatened at present.

Breeding         

Little terns are colonial breeders in coastal habitats. The nest is a shallow scrape that holds up to three eggs. The parents are monogamous and share the incubation and chick rearing duties.

Behaviour and ecology

Little terns in direct flight fly fast with steady beats of bent wings. When feeding, little terns pause in their patrols to hover on rapidly beating wings while looking down. From this position they may dive, often in very shallow water and the body rarely becomes fully submerged. Little terns often roost with small waders, especially wrybills. If several little terns are present they may roost and feed together as a flock.

Food

Small fish form the bulk of the diet but crustaceans, insects and worms have also been recorded.

Websites

http://en.wikipedia.org/wiki/Little_Tern

http://www.birdlife.org/datazone/speciesfactsheet.php?id=3276

References

Heather, B.D.; Robertson, H.A. 1996. The field guide to the birds of New Zealand. Viking, Auckland.

Higgins, P.J.; Davies, S.J.J.F. (eds) 1996. Handbook of Australian, New Zealand, and Antarctic birds. Vol. 3, snipe to pigeons. Oxford University Press, Melbourne.

McKenzie, H.R.; Sibson, R.B. 1957. Does the little tern (Sterna albifrons) reach New Zealand? Notornis 7:174-182.

NSW National Parks and Wildlife Service. 2003. Little tern (Sterna albifrons) recovery plan. NSW NPWS, Hurstville. http://www.environment.nsw.gov.au/resources/nature/recoveryPlanFinalLittleTern.pdf

Tennyson, A.J.D. 2010. Lari. Pp. 223-243. In Checklist Committee (OSNZ) 2010. Checklist of the birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica (4th edn). Ornithological Society of New Zealand & Te Papa Press, Wellington.

Recommended citation

Southey, I. 2013. Little tern. In Miskelly, C.M. (ed.) New Zealand Birds Online  www.nzbirdsonline.org.nz

Little tern

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Eastern little tern

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