Westland Petrels crashing in Greymouth after lights go out in Punakaiki

Monday, 21 December 2020

Weeks after street lights were turned off at night in a small West Coast community to help migrating Westland petrel chicks, environmentalists have a new conundrum – the little birds are now crashing further south.

Between November and January many fledglings leave their burrows in Punakaiki to embark on an 11,000km trip across the Pacific to South America.

Navigating by the sun, moon and stars, man-made light can disorientate them and cause them to circle back and crash-land.

In what is believed to be a New Zealand first, NZ Transport Agency turned off the street lights in Punakaiki from November to January when the fledglings leave their nest burrows.

However, the birds have since been found further south near Greymouth, often disorientated or killed.

In a phenomenon called “fallout”, they become confused by the light and crash-land on to road, where they are often severely injured, struck by cars or eaten by predators.

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Darrell Haworth, a Department of Conservation (DOC) senior biodiversity ranger, said Greymouth was seeing more downed birds than normal.

This season staff have picked up 22 Westland petrel fledglings in the area, where previously the highest number was 10 birds.

Seventeen were able to be released, four were found dead and one was put down because of its injuries.

However, the lights being turned off in Punakaiki meant they had only seen 10 petrels crash there, instead of the usual 15 to 25.

The reasons behind the increase in Greymouth remain unclear.

“It’s not as simple as just they have moved south,” Haworth said. “It’s more that we are getting a higher number in the Greymouth area and for the first time we are getting them in the CBD.

“Our usual areas are still getting them, just in higher numbers.

“Whether lighting is the direct cause of all the Greymouth birds crash-landing is not clear, however most cases can be linked to lighting in the area, including lights on businesses and other private properties.”

Haworth encouraged West Coasters to turn off unnecessary lights during the fledgling season and urged people not to try to help any fallen birds they find, but to contact DOC.

“We need to check the birds over before we take them for release, to ensure there are no injuries to the bird.

“And we need to know where birds are found so we can attempt to find the cause and work to mitigate if possible.”

There are about 6000 pairs of breeding Westland petrels in New Zealand, only doing so near Punakaiki, though they are found fallen anywhere from Westport to Hokitika.

The rise in the number of birds found near Greymouth alarmed Westland Petrel Conservation Trust chairman Bruce Menteath.

“There has always been some fallout in Greymouth but this year has been quite extraordinary,” he said.

“I understand there have been some changes to street lights in Greymouth that may have had an impact or it could be we have had an exceptional breeding season.”

Hundreds of birds are known to have crashed over the years, many of which are not found because they are eaten or crawl away to hide, become starved and are unable to launch again.

In 2018 the Grey District Council switched to LED street lights, which Menteath said had made the issue much worse.

“The West Coast night sky is as good as you can get in New Zealand so a lot of people were unhappy with the new brighter LED lights.

“There needs to be some planning around Greymouth for next season. We can't have that number every year.”

An NZTA spokeswoman said the Punakaiki trial was triggered by the replacement of six of 15 street lights last summer, and that the LEDs were more attractive to the endangered birds than the old lights.

People can call DOC hotline on 0800 DOCHOT/0800 36 24 68 if they find fallen birds.