New Zealand's disappearing bird species

Seagull is NZ's latest endangered species

Seagull numbers in New Zealand are falling so quickly the birds now appear on threatened species lists, alongside the kiwi and the kakapo.

Stuff,

30 October, 2014

A Department of Conservation report on bird numbers has classified the black-billed gull "nationally critical", the most serious category, usually reserved for our rarest birds, because of the rate of expected decline.

Numbers were predicted to drop by more than 70 per cent over the next 30 years.

There were an estimated 180,000 to 200,000 of the birds in 1977. There are now thought to be 60,000 to 70,000.

The red-billed gull, the mainstay of Kiwi beaches, is "nationally vulnerable".

Numbers have been falling sharply at the three main breeding colonies and are expected to drop by between 50 and 70 per cent over the next three decades.

The current population is thought to be fewer than 100,000.

The black-billed gull is found almost entirely in the South Island, mostly in Southland, living inland and nesting on braided rivers.

"Their numbers have crashed for some unknown reason," DOC bird scientist Hugh Robertson said.

Predators such as wild cats, stoats and ferrets were thought to be partly to blame.

Global warming could also be at play, Robertson said. It influenced changes in currents at sea, which affected food supply, and the water flow in rivers.

"The lower the flow, the islands [in braided rivers] are less defendable. It makes them more accessible to predators.

"You've [also] got weeds growing on the gravel so there's more cover for predators. They can get closer before they're detected."

Humans destroying habitat, through activities such as four-wheel driving, was a problem too, he said.

"I think people just see small gulls and think "just bloody seagulls" without realising they're part of native birdlife and have a right to be there."

Ornithological Society of New Zealand marine bird expert Graeme Taylor said gulls played an important ecological role in New Zealand, sustaining reptiles, invertebrates and rare plants such as Cook's scurvy grass.

"They may not be quite as popular as the kakapo because people think of them pooping on them and stealing their bread, but how many kids wouldn't get fun out of feeding seagulls down by the beach? If they were to disappear it would be quite a loss to the New Zealand coastal scene."

Taylor is leading a major count of red-billed gulls over the next year. Populations may have been falling even before the only other national headcount, in the 1960s, he said.

"Because it's a species that's quite long-lived it can take 100 years before you see a significant change in the numbers. As long as the adults aren't being killed, it will be a long, slow decline."

Seagulls can live up to 30 years. About 1500 red-billed gulls bred in nine small colonies on Banks Peninsula, Christchurch City Council ornithologist Andrew Crossland said, but thousands more flocked to the city to feed in places like the Avon-Heathcote estuary. Many came from the large breeding colony at Kaikoura.

"Christchurch is a major post-breeding wintering site for birds like the red-billed gull," he said.

"These birds rely on [the habitats of Christchurch] for half of their annual cycle."

He and his team would be measuring the local population for the national count and assessing the threat of predators.

Black-billed gulls used to be common in Canterbury, he said, nesting in many braided rivers like the Waimakariri, Rakaia and Ashley, but breeding was now limited largely to the Waimakariri.

"It's like the bottom's fallen out of the population."

BY THE NUMBERS

Black-billed gull: 1977: 180,000 - 200,000 birds. Now: 60,000 - 70,000.

Red-billed gull: Now: Fewer than 100,000 birds. Expected to fall by 50 to 70 per cent in the next 30 years.

FACTS

Seagulls live for about 30 years.

Black-billed gulls used to be more common than red-billed in New Zealand.

A young black-billed gull has a reddish beak. A young red-billed gull has a black beak.

There are three major breeding colonies for red-billed gulls: Kaikoura, the Mokohinau Islands in the Hauraki Gulf and the Three Kings Islands north of Cape Reinga.

Black-billed gulls are endemic to New Zealand. 

Populations of the two New Zealand wandering albatross species have declined by 50% in the last 10 years

Expedition to Subantarctic Antipodes Island

By Alison Balance

Radio NZ,

5 February, 2015

Antipodes Island scenery: view down to South Bay; expedition members waiting out a snow squall; and view of the hut and the large peat slip that came down the hill behind in January 2014. = Photo: RNZ / Alison Ballance

Sign on the hut at Antipodes Island.- Photo: RNZ / Alison balance

It's wind-swept, storm-lashed, hard to get to and difficult to walk around on, but uninhabited Antipodes Island is a remarkable gem. Its parakeets hang out with penguins, it's the only place in the world where Antipodean wandering albatrosses breed, it's home to hundreds of thousands of seabirds, and it's a stronghold for erect-crested penguins. If it wasn't for the mice it would be perfect. But an ambitious project - lead by the Department of Conservation, the Million Dollar Mouse project and WWF - is underway to rid Antipodes Island of its unwanted rodents, and the first advance parties are already heading there to make sure everything is set up.

More than 800 kilometres from mainland New Zealand, Antipodes Island is the most remote of New Zealand's five subantarctic island groups. Mice have been on the island for 100 or so years. They probably arrived accidentally, along with sealers or ship-wrecked sailors. There have been three wrecks on the island, although in both the early cases the marooned sailors were rescued. The old Government castaway depot, built in the late 1800s to provide shelter for such emergencies, still stands.

Antipodes Island wildlife: Antipodes parakeet in a penguin colony; an Antipodean wandering albatross chick; and a skua eating a sooty shearwater. -Photo: RNZ / Alison Ballance

In January 2014 the castaway depot was pressed into service for albatross researchers Kath Walker and Graeme Elliott. Arriving for their annual breeding census of wandering albatrosses they discovered that the research hut had been knocked off its piles, shunted 20 metres and swung through 90 degrees by a large debris slip which had come down from the hill behind. Large amounts of vegetation, peat and the hut's water tank had slid over the cliff into the sea. The slip was just one of many slips, covering 15% of the island's area, that had occurred following a very heavy rain event sometime in early January. Judging by old slip scars, major slip events like this are a common event on the peat covered island, which has no trees but rather a tussock, fern and megaherb dominated vegetation growing on a thick layer of peat that is much undermined by seabird burrows.

The hut is of key importance for the mouse eradication - planned for winter 2016 - necessitating urgent and extensive repair work. The hut was stabilised and made watertight by the Navy when they visited the island to pick up Kath and Graeme, who had begun the task of digging peat away from the hut and diverting water. In August 2014 an expedition headed to the island with building materials in an effort to rebuild it, but they were unable to land for more than a week due to strong winds and high seas. They eventually got the material ashore, but were unable to make much headway on the repair job.

In mid-October, Alison Ballance joined a spring expedition to the island which had two main tasks: re-pile and rebuild the hut, and re-survey the penguin colonies, which appeared to have been significantly affected by the slips.

Penguins on Antipodes Island: erect-crested penguins (left); Denise Fastier counting penguins; and rockhopper penguin incubating an egg (right). - Photo: RNZ / Alison Ballance

The erect-crested and rockhopper penguin colonies which ring the island's coast numbered about 40,000 breeding pairs when they were counted in a ground survey in 2011. The intention is to resurvey the penguins every five years, but it was decided to resurvey them earlier to quantify the damage caused by the slips. 

The 5-yearly census was begun to monitor long-term population trends, as there have been significant declines in penguin numbers since occasional surveys began in the 1970s. Judging by photos, many previously large colonies have shrunk significantly in area.

The results from the 2014 spring count, which was timed to coincide with the incubation period of the erect-crested penguins, showed an overall decline in breeding pairs of 19% compared to 2011. Colonies that weren't affected by slips had declined by 13%, while slip-affected colonies were down by 24%. Numbers of breeding penguins vary between years, so it is too soon to say yet whether the downward trend is a long-term one, but it is clear that the slips have had a short term impact on penguin numbers.

Out of 89 nests that were check in the Antipodean wandering albatross study area, there were 26 failed nests. Sixty three chicks were banded; this is low compared to the early years of the study, but quite good for the last couple of years. The researchers don’t know why the population has dropped so much – it may be something to do with food supplies out in the ocean.

2000-hectare Antipodes Island is a National Nature Reserve and a World Heritage Site. The Antipodes Island mouse eradication is scheduled for the winter of 2016, and is a joint project of the Department of Conservation, the Million Dollar Mouse project and WWF.

The 2014 Antipodes Island spring expedition in front of the re-built hut. - Photo: RNZ / Alison Ballance

The spring expedition travelled to and from Antipodes Island on the 25-metre yacht Evohe, skippered by Steve Kafka. Expedition members (left to right in photo above): Jo Hiscock, Brian Rance, Dan Lee, Denise Fastier, Geoff Woodhouse, Kathryn Pemberton, Cullum Boleyn, Andy Turner,  Alison Ballance and Mark Le Lievere.

A sister story on the expedition's visit to the Bounty Islands will air on 19 February 2015.

The following subantarctic stories have featured on Our Changing World previously:

The loneliest tree on Campbell Island

Our Changing World - the world's loneliest tree ( 10 min 18 esc )

Veronika Meduna joins a scientific expedition to Auckland and Campbell islands

Exploring New Zealand's Subantarctic Islands ( 51 min 56 esc )

Alison Ballance joins an expedition to the Auckland Islands to count yellow-eyed penguins

Yellow-eyed Penguins at the Auckland Islands ( 26 min 35 esc )

Kath Walker and Graeme Elliott have been studying Gibson's wandering albatrosses on Adams Island since 1991

Wandering Albatrosses ( 18 min 47 esc )

Alison Ballance bands Gibson’s wandering albatrosses, and hears from Kath Walker and Graeme Elliott how populations of the two New Zealand wandering albatross species have declined by 50% in the last 10 years.

Wandering Albatrosses ( 19 min 17 sec )