Fairy tern  (Sterna nereis)

Classified as Vulnerable (VU) on the IUCN Red List (1).

Weighing just 70 grams at maturity, the fairy tern is one of the smallest terns breeding in Australasia (3) (4). During the breeding season, this diminutive seabird has a black crown, pale grey upperparts, a white forehead, throat, chest and belly, an orange/yellow bill and orange legs (2) (3) (4). With the onset of the non-breeding season, the crown fades into a mottled black and white, while the bill and legs become duller in colour (3) (4). The sexes are alike in appearance, and juvenile fairy terns have a similar plumage to the non-breeding adults (3). Three subspecies, which occupy different parts of the fairy tern’s overall range, are recognised: Sterna nereis nereis, S. n. exsul and S. n. davisae (2) (5).

The subspecies Sterna nereis nereis occurs in Western Australian, South Australia, Tasmania and Victoria; S. n. exsul is restricted to New Caledonia; and S. n. davisae is only found in northern New Zealand (2) (5).

The fairy tern usually breeds on sandy beeches on sheltered mainland coastlines and nearby islands (2).

Feeding almost entirely on fish (2), the fairy tern hunts on the wing, hovering three to ten metres above the sea surface, before plunging steeply into the water, emerging again seconds later. In addition to fish, crustaceans, plant material and snails have also been found in the stomach of this tern (3).

Whilst the fairy tern breeds in colonies in Australia, some of which can be fairly large (3), in New Zealand breeding pairs generally nest alone, with gaps of up to several kilometres between nests (5). Usually one to two eggs are laid each season (2), except in the event of a lost clutch, in which case pairs generally re-nest (5). Both sexes share incubation duties, and, after hatching, care of the chicks (3). After fledging, the young remain with the parent birds for several months, during which time they learn to fish for themselves (5).

The migratory habits of the fairy tern are poorly understood, with some populations migrating over winter, such as in Tasmania, whilst others appear to remain in the same area year round (3).

Over large parts of its range, the fairy tern is subject to a variety of threats, including predation by introduced species, habitat degradation through development and farming, human disturbance, and extreme weather events (2) (4) (5). Of the three subspecies, the New Zealand fairy tern is most at risk, with a population that has teetered on the brink of extinction since the 1970s, and is currently recognised as the country’s rarest indigenous breeding bird. Despite being relatively widespread and common in the 19th century, the New Zealand fairy tern plummeted to just three pairs, at three separate breeding sites, in 1984 (5) (6). Fortunately, in response to intensive management, the number of breeding pairs has slowly increased, with the New Zealand population estimated at around 35 to 40 individuals as of 2006 (2) (5) (6). Although the population in Australia is considerably larger, with the number of mature individuals estimated in the low thousands, it has declined rapidly over the last thirty years, particularly in South Australia, where inappropriate water level management has led to a collapse in prey species. Less information is available on the New Caledonian subspecies, but numbers have certainly declined, with just 100 to 200 pairs remaining (2).

The rebound in the New Zealand fairy tern population since 1984, is attributable to the fencing off of nesting sites, and the work of wardens and volunteers who maintain the fences and trap predators (4) (5) (6). The latest recovery plan for the New Zealand subspecies, which was approved in 2005, sets out measures to increase the breeding population further. Some of the key recovery actions include continued protection of nesting sites, predator control, habitat enhancements, and the improved usage of captive breeding facilities (5). In Australia, many colonies are regularly monitored, and proposals have been made for more rigorous conservation measures such as those already in practice in New Zealand (2).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of the fairy tern, see:

• New Zealand Department of Conservation:
  http://www.doc.govt.nz/conservation/native-animals/birds/sea-and-shore-birds/nz-fairy-tern-tara-iti

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org