Last call for five-yearly native bird threat level updates

Monday, 25 January 2021

A cat has been captured taking a banded dotterel from a nest at South Bay, Kaikōura (first published October 2020).

Conservationists are calling for more practical steps to protect vulnerable native bird populations, as a review of just how endangered each species is looms.

Submissions close for the New Zealand Threat Classification System’s (NZTCS) review of the threat level of native birds at the end of the week.

The review, carried out by an expert panel, happens every five years.

* Banded dotterel slaying 'a devastating loss' for Kaikōura study

Only two chicks have survived to adulthood this season in Kaikoura’s South Bay banded dotterel population.

* Return of 'clumsy' bittern prompts driver caution on Coromandel causeway

Volunteer researcher Ailsa Howard, who monitors the banded dotterel population at Kaikōura’s South Bay, will be making a submission calling for the species’ threat level to be raised.

Kaikoura researcher Ailsa Howard monitors an area of South Bay beach for tiny banded dotterel.

“In the last three years at our site, we’ve had a 30 per cent decline … that's a third of our birds in two breeding seasons,” she said.

The local flock built 46 nests in the area this summer, but nearly all were wiped out by cats.

The Australasian bittern can be found on both sides of the Tasman Sea, but is critically endangered in Australia too.

Howard initially feared the season would be a “total nesting failure”, but two chicks, named Christmas and Miracle, have made it to adulthood.

With numbers of banded dotterels estimated to sit anywhere between 40 and 17 thousand birds nationwide, she said it was easy to assume the species would be OK.

“But we need to look closer, because the species is in decline.”

Howard said while a lot of energy could be put into trying to measure population sizes, she would prefer to see action.

“We know what the vulnerabilities are, and we know they are profoundly impacted by predation.

Ecologist Peter Langlands says meaningful wetland restoration work is the only way to save the bittern.

“But if the predation threat was managed, the populations could bounce back. There’s still an opportunity, but they won’t recover without help.”

Independent researcher Peter Langlands has been monitoring Canterbury’s population of a bird considered even more endangered – the Australasian bittern – and has provided his data to the Department of Conservation (DOC).

The bittern was added to the 'nationally critical” category in the last review, and there are thought to be less than a thousand left nationwide.

“The birds are in big trouble.”

Langlands said the population had continued to decline, with the number of males heard “booming” for mates at Lake Ellesmere’s Harts Creek halving from eight to four.

The Department of Conservation raise young Black Stilt, or Kaki, in captivity in Twizel.

The loss of their wetland habitats was one of the biggest issues.

“Our wetlands are suffering a death by a thousand cuts. There is so much degradation, but so little in terms of protections or enhancement.”

The bird's saving grace, he said, was that they could travel extremely long distances.

One he was monitoring even flew from Te Waihora-Lake Ellesmere to the Wairau Lagoons in Marlborough – a journey of about 350 kilometres.

“But deaths from collision events are also becoming more common, and it’s suspected to be caused by bittern having to move between habitats.

“Starvation’s also becoming an issue. It killed several chicks this spring.”

The only solution, he said, was to start investing in meaningful wetland restoration, or creating new wetland habitats to save them.

Langlands said bitterns were the apex predator in wetland environments, and needed a steady supply of small eels, frogs and fish to feed on.

It is not bad news for all species though.

DOC’s Kakī – or black stilt – Recovery Programme has seen numbers of the critically endangered Mackenzie Basin native more than double since the last review.

Biodiversity supervisor Cody Thyne said the population had risen from 77 birds in the wild to 169.

The programme involves field staff collecting eggs from wild pairs and bring them to a captive facility near Twizel, supplemented with eggs collected from five captive pairs.

“Without the intensive captive rearing and release programme, it has been estimated kakī would potentially go extinct within eight years.”

The expert panel would have access to their data, Thyne said, but they were not expecting a change to the vulnerable bird’s threat level yet.

“If we can get them to between 250 and 1000 adults and continue the population trend, then their threat ranking can be re-assessed, and will most likely then be categorised as recovering.”