A NZ fairy tern drops in to Omaha
On 26 November, 2009, a New Zealand fairy tern (NZFT) was sighted roosting on Omaha Spit. Photos taken by Marie Ward confirm it as a second summer bird and it was one of a small group of immature NZFT regularly recorded at the Pakiri breeding site in the preceding months. Interestingly, Marie snapped the same individual, again at Omaha Spit, on 22 December 2010.
In November, when resident NZFT breeding pairs are laying their eggs, they are less tolerant of "hangers-on", such as last season's chicks or other unpaired adults. Such unpaired/immature birds have frequented Omaha Spit for a couple of weeks in the past: once in December in the mid 1990s and again in November in the late 1990s. Early this century Simon Chamberlin recorded a juvenile NZFT (only months old) at Omaha one March. This youngster was probably just beginning his "walkabout" in the great wide world (see below).
The NZFT is New Zealand's rarest indigenous breeding bird, the population numbering c30-35 individuals (circa 2013). It has a threat ranking of Nationally Critical. It was once widespread around the North Island coast and some South Island rivermouths, but now breeds at only four locations, Waipu, Mangawhai and Papakanui Wildlife Refuges and Pakiri River Mouth in the upper North Island. Like New Zealand dotterels, NZFT nest in exposed areas of beach. The nest of 1-2 eggs is a shallow scrape above the spring high tide mark, usually on a slightly raised open patch of shell, without any large beach debris or vegetation close by. This gives the incubating bird a 360 degree clear view of any approaching threats. Fairy tern pairs nest alone and rely on their colours (and that of the eggs and chicks) to blend into the beach. Ironically, their superb camouflage leaves them unseen and therefore vulnerable to human activities on beaches.
Young chicks are fed by parents at intervals during the day. When the chicks can fly, the family moves into the nearby estuary/river where the chicks learn to bathe, preen and catch small fish. Fairy terns hunt by sight, picking up on the movement of fish. They hover 5-15 metres above the water and make shallow plunge dives to secure prey items, not totally immersing their bodies. Having learned basic survival, juveniles go walkabout during their first year of life. Most NZFT flock in the Kaipara harbour in winter.
The causes of decline are attributed to a variety of factors:
1) Habitat modification of breeding, foraging and roosting sites (related to the development of forestry, residential subdivisions and encroaching vegetation).
2) Loss of chicks and eggs, due to disturbance by humans and dogs.
3) Predation by introduced mammalian predators, particularly rats, mustelids, cats, hedgehogs, and native avian predators (Black-backed gulls and Australasian harriers).
4) Adverse weather events e.g. cyclones, can impact on productivity each breeding season.
Under the Department of Conservation's New Zealand Fairy Tern Recovery Project, all unfledged chicks are individually colour banded. Protection measures, e.g. predator trapping, erecting temporary fences and signs and regular patrols, are undertaken by DOC wardens and volunteers. Detailed statistics such as seasonal movements, seasonal pairings, nesting outcomes, behavioural interactions and predator kill totals are all recorded. Candling of eggs to ascertain fertility and moving eggs between nests/pairs to maximise productivity is carried out each season by DOC officers. Auckland Zoo provides a back-up incubation facility for threatened or rescued eggs. Captive rearing of NZ fairy tern chicks, although attempted in the 1998/99 season, is not part of the Recovery Project yet.