The Fairy Tern Sterna nereis is predominantly an Australian breeding species but subspecies do occur in New Zealand and New Caledonia. In Australia, subspecies nereis may number less than 5,000 mature individuals at up to 170 sites, with less than 1,600 pairs in Western Australia, a few hundred pairs in each of Tasmania and South Australia and just a few pairs in Victoria. Though it may be stable in Western Australia, numbers elsewhere in Australia have declined rapidly during the last thirty years.
In New Zealand, davisae plummeted to three pairs in 1983 but, due to intensive conservation efforts has increased and in 1998, totalled 25-30 birds and 8-10 pairs over three sites, and in 2006, 35-40 pairs. In New Caledonia, exul numbers 100-200 pairs, but was formerly much more abundant. Data indicates a decline of 23% due to, perhaps most importantly, disturbance and predation.
Fairy Terns have been up-listed to ‘Vulnerable’ under the 2010 IUCN Red List status owing to recent declines over much of its breeding range. Predation by introduced species, disturbance and inappropriate water level management are thought to have contributed most to this decline. However, data is patchy, and a clarification of trends in its strongholds may lead to its status being revised.
In New Zealand, intensive management currently includes trapping mammalian predators, fencing of nesting sites to reduce disturbance, the employment of wardens over the breeding season, colour banding of all chicks, and egg and chick manipulations to maximise productivity. Population modelling has indicated that these management actions have halted the decline, resulting in an increase in the population of 1.5% per annum and reduced the calculated risk of extinction within 50 years from 52% to 39%.
In the northern part of its range the Fairy Tern appears to be an early spring breeder. August is the earliest record for the Dampier Archipelago. In the south it breeds in the early spring from September through to March. Later nesting may be due to disturbance. Eggs are pale with blotches of dark brown. Nests are located on the ground in a scooped out hollow. When chicks hatch they remain near the nest site but later move away and seek shelter in seaweed or other cover. The diet of Fairy Terns predominantly is fish. Other food items that have been recorded are gastropods, crustaceans and plant material.