Is the seafaring grey-backed storm petrel making itself at home in the Southern Alps? Scientists want your help to find out.
THIS IS A CALL-OUT TO ALPINISTS. PLANNING ON CLIMBING IN THE SOUTH ISLAND? DOCTOR COLIN MISKELLY NEEDS YOU. THERE MAY BE A MOMENT YOU’RE LEAVING YOUR TENT OR YOUR HUT WELL BEFORE DAWN, HEADLAMP LIGHTING THE WAY. SUDDENLY THERE’S A MOVEMENT IN THE TORCHLIGHT AND SLENDER WINGS APPEAR, BEATING FURIOUSLY. THEN A TINY BIRD, INNATELY CURIOUS, MIGHT EVEN COLLIDE WITH YOUR HELMET OR SHOULDER. TAKE NOTE, WATCH WHERE IT GOES, AND SEE IF YOU CAN IDENTIFY ITS COLOURING. BECAUSE THIS COULD BE THE SMALLEST NEW ZEALAND SEABIRD OF THEM ALL, THE ELUSIVE AND ENIGMATIC GREY-BACKED STORM PETREL (GARRODIA NEREIS).
“In terms of people recognising them, they’re tiny and delicate, like a feathered butterfly.” Colin says. “You could hold them in the palm of your hand. They’re so lightly built, a puff of wind would blow them away.”
Colin’s official title at the Museum of New Zealand Te Papa Tongarewa is ‘Curator of Vertebrates’. He’s followed birds, specialising in New Zealand seabirds, most of his life, utterly determined to understand and record as much as anyone can in the realm of seabird science.
Seabirds (particularly those usually confined to the subantarctic) and the mountains of Aotearoa may seem like an unlikely mix, which makes the story of the grey-backed storm petrel so much more intriguing. But it’s the high alpine areas of the Main Divide and the Fiordland mountains where seabird scientists are now looking to, to find where this diminutive power-house of an endemic petrel might nest, and how on earth (quite literally) it can survive there. This was a bird that was known to nest hundreds of kilometres away, on the Chatham, Antipodes, Auckland and Campbell Islands. What could have drawn them here, more than twenty kilometres from the open ocean, in an area surrounded by high mountains, to Fiordland?
I joined Colin, and other scientists, documenting stage three of a seabird survey in Fiordland in late 2019, on the islands of Te Puaitaha / Breaksea and Tamatea / Dusky Sounds. On a number of nights we sat up on the top deck of the Department of Conservation vessel, the Southern Winds, searchlight beaming up into the sky. Petrels are attracted to the light. Sadly, the moon was near full, and we only saw a sooty shearwater, the tītī / muttonbird (Ardenna grisea).
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But we knew there had been a conclusive sighting here, in the spotlight, on a 2016 survey. Moored at the head of Wet Jacket Arm off Acheron Passage, near midnight on a misty night, Colin and his colleagues identified the unmistakable shape and colouring of two grey-backed storm petrels.
Grey-backed storm petrels have been found in the Southern Alps more than once over the last few decades. In 1978, three birds were located, sadly deceased, on the slopes of Tititea. In 1982, ranger Kim Morrison found a live grey- backed storm petrel near the Howden Hut on the Routeburn Track, and carried it down and released it, fit and well, into Milford Sound. And Colin Miskelly himself discovered another deceased petrel on the Routeburn Track when walking with his wife in 2018.
But it was on Colin’s last voyage and seabird survey in Fiordland in November 2020, that the results and sightings were conclusive, and something of a gift. This last survey took in all the islands from Doubtful Sound north to the entrance of Milford Sound. It was no leisurely boat cruise with binoculars; a seabird survey is action-packed, physically arduous and sometimes verges on perilous. Surveying the islands often means landing in rough seas onto rock and kelp-covered outcrops, a leap from a moving dinghy followed by a fast climb wherever a foothold or handhold can be gripped to escape the next crashing swell. As soon they reach likely terrain–dirt, scrub, forest if they’re lucky–the scientists go onto hands and knees, grovelling in mud, arms down burrows.
Seabird scientists talk about ‘GISS’, meaning ‘General Impression of Size and Shape’, an expression coined in World War II to identify enemy aircraft. But on the 2020 survey in Fiordland they had no need for GISS; the scientists got right up close and personal with the beautiful, grey-backed storm petrel. Each night, they had several encounters and observations of the birds in the spotlight, but it was on the last night of the survey that Colin had the gift from above. They were moored in Hall Arm, at the head of Doubtful Sound, 40 kilometres from the open ocean. Colin, being an early riser (and forever diligent), was working in the dark of the saloon well before dawn, on his laptop. The back door to the open deck of the Southern Winds was open, and suddenly, a storm petrel flew in, attracted to the light of his computer, and hit him in the chest.
Adding to the intrigue was that this bird (now in the hand), and one of the others they’d caught, had a bare “brood patch”, its abdominal area with no downy feathers, allowing efficient transfer to keep an egg or chick warm. “The likely explanation is that it had just completed an incubation shift and had flown down from the surrounding mountains to sea level, before heading out to the outer coast before dawn to feed,” Colin explains.
If so, and if there really are grey-backed storm petrels in reasonable numbers nesting above the bushline in Fiordland, how do they survive predation from stoats?
Survival or successful nesting is a game of geographical roulette, dependent on whether rats or stoats are present. On islands with predator control in Tamatea / Dusky Sound, the seabirds are back in good numbers on many islands. North of Doubtful, it’s either islands with predator control (stoat traps), or those well out to sea, where the scientists are finding reasonable numbers.
Of the birds who nest (or burrow) in Fiordland, tītī is one most of us recognise. Mottled petrel (Pterodroma inexpectata) is a prize-winning aviator, flying all the way to the Bering Sea near Alaska, then to the Antarctic sea ice and back to the same nest every year. And my personal favourite, the broad-billed prion (Pachyptila vittata). It’s also known as ‘blue billy’, for the distinctive blue sheen on its wings. The distance each can fly to find food is staggering (often to the Antarctic convergence zone), as is how they feed (skimming the surface for plankton), and their ability to navigate directly back to their natal cliff or island. New Zealand landbirds may take the spotlight, but it’s the seabirds, often overlooked, who have the most fascinating story to tell of all.
Colin questions why grey-backed storm petrels hadn’t been previously reported in the area over the last century, at least by fishermen. He wonders if they were simply not noticed in Fiordland because they look like “just another petrel” in varying shades of grey. Hence the very particular call-out now.
Most climbers will be familiar with the whistle of a rock wren, and have seen their inimical flit across a rock slope. But rock wren are becoming increasingly rare, the tiny alpine avian seriously endangered from predation by stoats. Also on the decline is the kea, inhabiting the alpine zone but nesting just below the bush line, its nests also a ready smorgasbord for the mustelid. How is it, then, that a mainly subantarctic-inhabiting tiny petrel, could survive the same predatory conditions?
Colin wonders if it has found rock ledges or corners where stoats, however proficient their alpine skills, simply cannot get to. And if that’s the case, where? He admits the nests would be almost impossible to spot. “They don’t need much real estate, two or three petrels can tuck themselves under one tussock.” But he’s putting the call out to all alpinists just in case they come across a bird, or even better, a nest. And if you do, the best way to report a sighting? Go on to the website, iNaturalist.org, or ring Colin, just now and then back at his desk at Te Papa.
It’s heartening that as so many of New Zealand native birds are in decline, there appears to be one species finding what could be a safe niche in the most beautiful corner of all, the mountains of Aotearoa. But like so many mysteries surrounding our seabirds, that remains to be confirmed. Let’s hope.
WORDS: PETA CAREY
PHOTOS (except where noted): Jean-Claude van Stahl
