One of New Zealand's rarest birds, the tara-iti or fairy tern, has had a successful summer breeding season, with seven chicks expected to fledge.

With fewer than 40 adult birds, and most in Northland, the tara iti/fairy tern is critically endangered and, despite intensive management, has teetered on the brink of extinction since the 1970s.

"Seven chicks [to leave the nest] is a great season. Last year [2018-2019 season] we only had two chicks fledge, so this is a big improvement, but more of what we would hope to call an average season," Department of Conservation (DoC) biodiversity ranger Ayla Wiles said.

"The settled weather during the season resulted in fewer nest loses than last season and overall the birds finished laying earlier. The major challenges this year have been the loss of at least one of the parents of two chicks at Te Arai and the subsequent loss of one of those chicks, the loss of a fertile egg to a rat at Waipū, and the desertion of a chick by its parents halfway through the dependency period at Mangawhai.

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"We have also had higher incidences of compliance issues causing disturbance to the birds. Common problems have been dogs in DoC-administered reserves and wildlife refuges and Auckland Council land where they are not allowed by law, horses in areas they shouldn't be, vehicles, drones, low flying paragliders, jet skis, fizz boats, and aircraft causing disturbance as well as small fires threatening the nest sites.

"These causes of disturbance are common to most of our shorebirds, not just the tara iti."

Tara iti/fairy terns nest on shell and sand banks above high tide, which leaves them vulnerable to predators, disturbance by people, 4WD vehicles and dogs.

Ayla Wiles, from DoC, and Ari Carrington, from Patuharakeke, among the shell and sand mounded to create a perfect nesting site for the Fairy Terns at Waipū last year. Photo / File
Ayla Wiles, from DoC, and Ari Carrington, from Patuharakeke, among the shell and sand mounded to create a perfect nesting site for the Fairy Terns at Waipū last year. Photo / File

A dedicated team of six fairy tern DoC rangers and numerous community volunteers have been busy since September trapping predators near nesting sites, fencing off nesting sites and preventing nesting birds from being disturbed by humans. The rangers and volunteers will finish the intensive stage of work shortly.

Once widespread around the North Island and on the eastern South Island, the New Zealand fairy tern now breeds at only four main nesting sites, at Papakanui Spit, Pakiri Beach and Waipū and Mangawhai sandspits, as well as a fifth site at Te Arai this year.

DoC works closely with Patuharakeke, Ngāti Whāuta o Kaipara, Ngāti Manuhiri and Te Uri O Hau, Shorebirds Trust, The NZ Fairy Tern Charitable Trust, About Tern, Birds NZ, and the Waipū About Tern Trappers to help protect the New Zealand fairy tern.

Tara-iti / fairy tern

• This small, dainty coastal tern is the most endangered of New Zealand's endemic birds.

• The relict population survives between Whangārei in the north and Auckland to the south.

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• The tiny population is gravely threatened by introduced predators and disturbance or encroachment by humans. The birds are intensively managed during the breeding season.

• Fairy terns are confined to Australia, New Zealand and New Caledonia, with endemic subspecies in each country.

• Fairy terns breed successfully at four sites only in New Zealand: Waipū sandspit, Mangawhai sandspit, Pakiri River mouth (one pair since 2003), and Papakanui sandspit on the southern headland of the Kaipara Harbour.

• Since 2012, birds have occasionally nested at the Te Arai Stream mouth, just south of Mangawhai.