1 Feb 2016

Endangered birds threatened by mangrove removal

9:10 am on 1 February 2016

The critically endangered fairy tern could disappear from the Mangawhai harbour in Northland if a local group keeps removing mangroves, conservationists say.

Fairy terns in flight at Mangawhai

Fairy terns in flight at Mangawhai Photo: Sioux Plowman

The Mangawhai Harbour Restoration Society was given consent to clear some mangroves from the middle of the harbour in 2012, and earlier this month they announced plans to remove more.

The fairy tern is New Zealand's rarest endemic breeding bird with half of its 10 breeding pairs living in Mangawhai, and the restoration society's plans put the birds at risk, said Forest and Bird's seabird conservation advocate Karen Baird.

"The problem in this situation is it's very hard to prove that something is going to happen, but what you have to do is you have to look at the risks," said Ms Baird.

"And the risk with this situation is if you mess around too much with that harbour, you are going to contribute to the potential extinction of that bird - which is already on the edge."

The birds nest on the beach and forage for small fish called 'gobies' that live in the mangroves, to feed themselves and their chicks.

Fairy tern with chicks at Mangawhai

Fairy tern with chicks at Mangawhai Photo: Sioux Plowman

Only two chicks hatched in Mangawhai's last breeding season, the lowest number in several years.

There was no doubt more mangroves equalled more fish for the fairy tern, and not enough would mean a poor breeding season, Heather Rogan from the New Zealand Fairy Tern Trust said.

"The male birds feed the female birds with fish, they've been observed feeding up to 100 or so in a couple of hours so the female can produce eggs, so if there aren't enough fish in the harbour for that to happen then they simply don't produce eggs," Ms Rogan said.

"A bit later in the season if there's not enough fish in the harbour, they might also abandon their eggs."

The Mangawhai Harbour Restoration Society needed to research the impact of the mangroves it had already removed before trying to get rid of more, Ms Rogan said.

"The harbour should be allowed to settle down and have no further disturbance until everything's been properly looked at... A proper scientific survey of all aspects of the harbour management should be undertaken before any further work is done."

Mangawhai Heads (Harbour)

Mangawhai Heads (Harbour) Photo: Flickr user Sids1 / CC BY 2.0

The Mangawhai Harbour Restoration Society's president Trevor Downey said the group would seek independent research on the mangrove removal before proceeding.

The society wanted to work with conservation groups to achieve their vision of restoring the harbour back to how it was in the 1950s, which was clearer and cleaner, Mr Downey said.

"Our passion is the harbour and the habitat, the birds as well, I mean we spend a lot of money planting the sand dunes out to protect the birds and stop the sands from shifting and we do the pest control," he said.

"We do everything we can to make things right, we're not out to destroy anything - what we're trying to do is restore our harbour to how it was."

But the group should be more aware about the biodiveristy and ecological importance of the mangroves, Forest and Bird's Karen Baird said.

"The fairy tern is already critically endangered, so why would you mess with a system you don't even understand?" Ms Baird said.

"The Mangawhai Restoration Society don't even recognise that removing the mangroves might have an impact on the fairy terns, and we're really concerned about that."

A public meeting is being held in Mangawhai on March the 19th to discuss future plans for the harbour.