By Tracy Neal of RNZ
The mystery of why native Westland petrel fledglings keep crash-landing on the West Coast continues, after new LED street lights through Punakaiki were switched off to try to help them during their maiden flights.
Each year the fledglings leave the comfort of their coastal burrows, and fly to rich feeding grounds 11,000km east across the Pacific Ocean.
RNZ reported last summer the petrels were being dazed by bright new LED lights along the highway through Punakaiki, causing them to crash-land.
Waka Kotahi / New Zealand Transport Agency (NZTA) agreed to switch off the lights.
Westland Petrel Conservation Trust chair Bruce Stuart-Menteath said that it seemed to have lessened the problem in Punakaiki, but it was now worse further south in Greymouth.
"DOC told me they had at least 20 so far and we found another four squashed on the roadside - this is in Greymouth.
"I only found one squashed on the roadside in Punakaiki, so far this season."
The Department of Conservation said with the street lighting turned off in Punakaiki this year, 10 of the birds had crash landed there, instead of the usual 15 to 25.
In Greymouth, about twice the usual number had been picked up - 22 compared to 10 being the highest number previously, and for the first time they were found in the centre of town.
Stuart-Menteath said it was unlikely to be weather or climate related, given the La Nina weather conditions in New Zealand this season, and was more likely linked to confusion caused by LED lights which emitted a different colour spectrum to ordinary street lights.
"What happens is ... well, it's mostly fledglings for a start and they're very susceptible to bright lights on the ground.
"But when they crash-land, if they haven't injured or killed themselves, then they wander around looking for a launching site because they haven't got enough 'flap power' to lift themselves directly off the ground."
He said the birds might spend all night looking for a launch site, and then hide during the day.
"So they might be in someone's back yard, hiding in their vegetable patch or under a shrubbery, and then the next night they'll come out again and go through the same process - trying to find a launching site.
"Invariably they won't find one, so the next day they'll hide up, until they just exhaust themselves and die."
NZTA said it had no LED lights in Greymouth on State Highway 6, but in 2018 the Grey District Council switched to LED street lights in some areas.
DOC senior biodiversity ranger Darrell Haworth said they were keeping an open mind about what was causing the birds' confusion.
"We're a little bit reluctant to put the issue solely on street lights. I mean, there's a lot of floodlights in areas, a lot of business and commercial lighting.
"We've had a lot more (petrels) in Greymouth this year, yes, but what that's attributed to... we really need to have a look and map where all these occurred and go from there."
DOC said lighting was a documented cause of seabird fledging fallout in many species.
Haworth said it had prompted a plywood factory in Greymouth to turn off its spotlights during the fledgling season, to help the birds on their way.
Stuart-Menteath said it was possible more of the petrels were being found simply because more people now knew what they were.
"Instead of just driving past this 'black seagull' on the road and not thinking anything about it, people think 'oh! this bird's special - I better stop and pick it up'."
DOC said of the 22 petrels found in Greymouth, 17 were able to be released, four were found dead and one was euthanised.
Haworth said the birds were generally easy to manage and a "bundle of laughs".
While help from the public was welcome, it paid to call for help if someone came across an injured bird, he said.
"We've had some members of the public try and help the birds by popping them up on a seawall or what-have-you.
"The best bet is to just get hold of us and we can check it over and pop it somewhere nice and high so it can fly off again."
• The DOC Hotline is 0800 DOCHOT or 0800 36 24 68.