The New Zealand fairy tern or tara-iti (Sternula nereis davisae) is a subspecies of the fairy tern endemic to New Zealand. It is New Zealand's rarest native breeding bird, with about 40 individuals left in the wild. It nests at four coastal locations between Whangārei and Auckland in the North Island. It is threatened by introduced predators, extreme storms and tides, beach activity, and waterfront development.
Taxonomy and systematics
The New Zealand fairy tern is currently considered a subspecies of the fairy tern (Sternula nereis). Two other subspecies exist: Sternula nereis nereis, which breeds in western and southern Australia, and S. n. exsul, which breeds in New Caledonia. Fairy terns were first described from the Bass Strait in Australia in 1843. The New Zealand subspecies was first identified by Dunedin naturalist Thomas Potts in the Rakaia riverbed in Canterbury; it was breeding in the Rakaia Gorge. He noted there were already two specimens in the collections of Canterbury Museum. The New Zealand fairy tern is distinguishable from the other two subspecies on the basis of its morphology and behaviour, and has a distinct genetic haplotype. Genetic studies found there was almost no gene flow or migration between the New Zealand and Australian populations.
Distribution and habitat The New Zealand fairy tern was noted as being common in the late 19th century. However, these records have been suggested as inaccurate as the birds can be difficult to distinguish from little terns. From 1940 to 1983, the New Zealand fairy tern was known to have bred at several sites along the northern coastline of the North Island. Their breeding range extended from Ruakākā, in Northland, to Tauranga in the Bay of Plenty. New Zealand fairy terns were also reportedly found in Canterbury, in the South Island. However, from the mid-1970s, the population declined rapidly. By 1984, New Zealand fairy tern breeding was restricted to three sites in Northland: the Papakanui sandspit in Kaipara Harbour, the Waipu sandspit, and the Mangawhai sandspit. Currently, New Zealand fairy terns still occupy these breeding sites, with the addition of a new breeding site in 2012 at the Te Arai Stream mouth, south of Mangawhai. Forest & Bird is working to establish an alternative breeding site on the Kaipara harbour. In August 2018, the Department of Conservation and the New Zealand Defence Force worked to build a nest site ahead of the breeding season at Papakanui.
Ecology Unlike other species of terns which forage in the open ocean, the New Zealand fairy tern is not a plunge diver, but instead feeds in the top 5–8 cm of the water; it can capture prey in extremely shallow water such as estuaries and tidal pools. Adult birds have been observed feeding gobies (Favonigobius lentiginosus and F. exquisitus) and flounders (Rhombosolea sp.) to their chicks, and adult diet may include a substantial number of shrimps. Birds were observed foraging in Te Arai Stream, the mouth of which is a popular flocking for post-breeding fairy terns, but appeared to be getting most of their food from elsewhere.
Breeding Courtship begins in September, with egg laying occurring between late October and early January. Birds typically lay 1–2 eggs per nest.
Nests are small unlined scrapes in the sand and are roped off and monitored by The Department of Conservation. The nests are constructed near white, grey and orange shell debris to help disguise the eggs and chicks, and are found at least 1 km apart from each other. Guthrie-Smith describes a nest as follows:"On such a strip, sparsely sprinkled with little heaps of pebbles and surface shells in two and threes, lay the couple of eggs. These surface sea shells had been allowed to remain, as camouflage, untampered with, but from elsewhere had been also collected twenty or thirty other halves and wholes, showing deep lateral widths of purple and pink. Not a brilliantly tinted shell had been missed over the couple of acres I searched. The hen tern had then laid eggs to match the bivalves, the shells bright pink."Females spend more time incubating eggs than males, while males provide the majority of food to the chicks. The chicks are mobile from hatching, and ready to fully fledge from 30 days old. They are vulnerable to environmental events, such as storms, high tides, and predation. The encroachment of human activity on their nesting grounds (often, popular beaches) is a major threat to these birds. Beach narrowing, mainly due to housing developments and weed invasion, forces the terns to nest closer to the sea, putting their eggs at risk during storms. Introduced predators and human disturbance also threaten nesting sites. The wintering range of the birds extends over the Kaipara Harbour. Outside of the breeding season fairy terns form flocks on the harbour, often around Tapora.
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