Tern for the better for rare shore birds

These fairy tern chicks are still alive but not yet out of danger. They were born in different years, one on New Year's eve and the other on New Year's Day. Photo / Laura Patience/DoC

Northland's precarious fairy tern population continues to get help from birdminders ensuring the species doesn't slip over the brink of extinction.

Of this summer's clutch at four different nesting sites, so far at least five chicks have survived in the wild.

Department of Conservation warden Eliane Lagnaz said two have already fledged - are off the sand and flying around on their own; and a younger chick was banded last Monday, with two more due to be banded this week before they, too, learn to fly.

A pair at Mangawhai laid two viable eggs, with the chicks hatching in separate years - one on the last day of 2016 and the other on New Year's day 2017.

At Waipu, one chick disappeared in its first few days and one egg didn't hatch at all.

A chick also hatched at Papakanui, on Kaipara Harbour's South Head but it is not yet known if a second egg, still unhatched in the same nest, is fertile, Ms Lagnaz said.

"It's been really good weather-wise for a successful breeding season," she said.

The exposed scrapes in sand where fairy terns lay their eggs are often destroyed by high seas, predators, pets and, unwittingly, people.

None of this season's east coast sites have been reached and destroyed by high spring tides, nor have rough seas been driven up the sand by easterly winds, Ms Lagnaz said.

But, while signs and tape warned people to stay away, the big message to anyone living near the fully protected sites was to keep their cats inside at night, she said.

Cats were among the biggest threats to fairy tern chicks, but they also killed shore-dwelling native skinks and other wildlife.

Of the four known fairy tern breeding sites, three are in Northland - at Waipu, Mangawhai and Pakiri, while the other is Papakanui.

Six of the 13 fertile eggs laid this season were taken to Auckland Zoo for incubation.

Ms Lagnaz said while taking eggs from their exposed nests might save them from the elements and predators, transporting them also posed risks.

New Zealand Fairy terns (tara-iti) are thought to be the world's most endangered shorebirds and are "critically endangered".

There are fewer than 44 known to exist and a lack of breeding-age females is limiting the species' recovery.

In 1983 the number of fairy tern dropped to an all-time low of three or four breeding pairs.