Richard Robinson

Where the seabirds were

Once upon a time, raucous, stinking colonies of seabirds blanketed huge areas of Aotearoa’s mainland, each burrow and poo and eggshell helping fuel the forests. Those birds are gone now—but a new modelling tool gives a fascinating glimpse of what once was.

Written by       Photographed by Richard Robinson

Some of Willy Ngamoki’s earliest memories are of harvesting tītī chicks with his dad. It was the early 1960s, he was maybe five or six, and on autumn mornings father and son, like generations of Te-Whānau-a-Āpanui before them, would climb the steep-sided Pokohinu Point above Ōmāio Bay in the eastern Bay of Plenty.

His dad used a big thick leather glove and a mānuka stick to extract the chicks from the hole. Willy’s job was to listen and learn. But on one occasion a curved burrow entrance, with the chick sitting around a corner, meant the stick couldn’t be used, so Willy pulled the glove on—it reached all the way to his shoulder—and crawled into the hole. The chick bit the glove and latched on, and Willy’s dad pulled him out with the chick attached. He remembers the smell, the fluff.

One season, Ngamoki’s dad told him he thought the tītī were dying out. Each year, more and more burrows were cobwebbed over. “The vacancy signs were out everywhere,” says Ngamoki. “[Dad] said ‘That’s it, boy, no more birds.’ So we just hung the mānuka stick up.”

Today, Ngamoki, his brother and their cousins can remember where the burrows are, show you the lifeless holes. A few tītī still return to the point every year to lay eggs and raise chicks, but it’s a shadow of what Ngamoki remembers.

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Aotearoa is the seabird capital of the world, but its mainland is filled with ghost colonies.

For most New Zealanders, burrowing seabirds—the petrels, prions and shearwaters—remain at sea out of sight, and out of mind. This wasn’t always the case. Habitat loss has driven these birds from their historic homes on the mainland, while introduced predators have eaten away at once-vast populations. Multiple species have disappeared completely. What’s left is a fragment: a handful of grey-faced petrels on rugged Northland headlands, Westland petrels tucked into the West Coast, Hutton’s shearwaters huddled in the tussock above Kaikōura. For the most part, offshore islands are now the only safe places for seabirds.

“For most species, we don’t actually know the details of their decline or extinction,” says ecologist André Bellvé of the University of Auckland. “We just have some old information that they may have been in this spot—and then they disappeared. We don’t know when they disappeared or why they disappeared, but we can make pretty good guesses, and it does look like they can collapse pretty quickly.”

Efforts to establish an artificial colony of Hutton’s shearwater at Kaikōura Peninsula began in 2005. Colony manager Lindsay Rowe weighs each bird as it returns—86 adults arrived for the most recent breeding season.

Bellvé pores over old information for clues of collapse. He finds signs of petrels in peril in the notes of early naturalists, like Andreas Reischek’s accounts of tāiko. Reischek wrote of digging out a burrow with a tomahawk on Hauturu-o-toi/Little Barrier Island in November 1882 and attempting to collect an egg. When he was “severely bitten” in return, he set his dog on the bird. Two-and-a-half years later, Reischek returned, only to find the once-numerous feisty black birds had become scarce. “But I found the remains of many which pigs and dogs had destroyed,” he wrote.

By many accounts, Reischek was an unpleasant figure—an unscrupulous collector and graverobber—but these notes, and others from early naturalists, are the “lynchpin” in Bellvé’s efforts to reconstruct where our seabirds once were.

Many of the early naturalists’ accounts were derived from the kaitiaki of the places they visited. Across Aotearoa, te reo Māori place names remember long-gone seabirds: Tītīrangi in the Marlborough Sounds, referencing skies once filled with abundant tītī, and Motutaiko Island in Lake Taupō, the ‘island of the black petrel’. In Kaikōura, whakapapa expert Maurice Manawatu of the Ngāi Tahu hapū Ngāti Kurī tells histories recorded by his great-grandmother. She wrote of the first humans to arrive here, led by the ancestor  Rakihouia, who found the bay filled with millions of seabirds in a feeding frenzy. He watched them fly back up into the Kaikōura Ranges in the evening, and sent men to investigate. Here, they discovered vast breeding colonies of Kaikōura tītī, also now known as Hutton’s shearwater. The mountains were dubbed Kā-Whata-Tū-o -Rakihouia, the standing food stores of Rakihouia.

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Historically, the Kaikōura tītī were known to breed across as many as 16 colonies. They were even on Tapuae-o-Uenuku, a lofty peak further inland. Manawatu says kete and pāua used for tītī harvesting were found at the base of this sacred mountain. Today, the world’s only alpine-breeding seabird persists in just three colonies—two natural and one founded by translocation. “What we’re seeing is the final remnant,” says Alan Tennyson, curator of vertebrates at Te Papa. It’s a remnant that survives due to a stroke of topographical luck: “The main colony is in a strange basin bounded by cliffs, which is really hard for mammals to get into.”

There may be as many as four million fairy prions in New Zealand—but most inhabit offshore rock stacks and islands, like this flock captured off the Poor Knights. Only a handful make their home on the mainland, in the craggy cliffs of St Clair in Dunedin.

Sheer size also helped some species fend off predators and hang on longer than most—like the tāiko, among the largest of the petrels. Reischek reports visiting a colony in the Waitākere Ranges, in forested hills some 300 metres high and 20 kilometres from the sea. Tāiko were also found in burrows in the Heaphy Range of northwest Nelson in the late 19th century, their loud chattering earning them the nickname ‘night demons’ from diggers working in the area. Eggshells and feathers were found in the Hunua Ranges in 1989, a tantalising clue that perhaps mainland seabird breeding persisted—but it’s generally accepted that the last of the mainland stragglers only hung on until the 1950s. The last confirmed black petrel breeding on the mainland was in the Kaitake Range near New Plymouth, with a downy chick photographed in a burrow in February 1958. Now, Hauturu-o-Toi and Aotea/Great Barrier Island are the last refuges for tāiko, a species teetering on the brink.

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To figure out where petrels, storm petrels, shearwaters and prions—members of the Procellariiformes order—once lived, Bellvé gathered up these historic records and scoured old newspapers for mentions of seabirds. His collaborators, Trevor Worthy and Paul Scofield, compiled a database of natural seabird fossil deposits from the last 10,000-odd years, when the climate was relatively similar to today’s.

Using the fossils, the historic records and what we know about each species, Bellvé created a statistical model that predicts where burrowing seabirds might have lived in Aotearoa before humans arrived. The model spits out striking heat maps aglow with the ghosts of seabirds.

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Today’s maps are iridescent only on near-shore islands and at the very edges of the mainland, the thin strip of coastline where hangers-on cling to survival. But the maps of the past light up along the spine of the Southern Alps, the perilously perpendicular ranges of Fiordland, and the interior of the North Island as far as the volcanic plateau.

“What surprised me at first was birds on Ngāuruhoe and Ruapehu, and all throughout the Southern Alps. Like, what the hell are they doing there? It seems bizarre,” says Bellvé.

“You can see why people back in the 1800s would have remarked on that, because what is this seabird doing 300 kilometres inland on a mountain?” But of course, Bellvé notes, when you’re a seabird accustomed to flying thousands of kilometres across the Pacific Ocean, what’s a few dozen more to reach a good breeding spot?

It’s difficult to put an exact number on past mainland populations, but they were undoubtedly massive. “I’m sure there were millions of birds, tens of millions, maybe more,” says Tennyson. Graeme Taylor, a seabird scientist at DOC, concurs: “Probably hundreds of millions of birds—but there will be an upper limit, a carrying capacity determined by resources at sea.”

André Bellvé holds a fairy prion/tītī wainui during fieldwork on the Poor Knights Islands. While there to affix GPS backpacks to track the birds, Bellvé also collected faecal samples—when the birds cooperated. “​​We’re holding on to them and it’s no poo, no poo, no poo, and then they kangaroo-hop 10 feet away, stare at us and just shit into this very porous, loamy soil. It’s instantly unusable.”

Both Taylor and Tennyson speculate that historic seabird colonies on the mainland might not have looked like today’s densely packed island metropolises. On islands, it’s not uncommon to have one burrow per square metre across many hectares, but perhaps this is an artificial bunching up. “Maybe the birds have ended up concentrating, because that’s where it’s safe,” says Tennyson. “The main islands are so massive, birds can be spread really thin and still have tens and hundreds of millions of them. They don’t have to be every square metre.” In particular, seabirds of smaller stature—like storm petrels—may have dispersed to reduce the chances of being eaten by predators like ruru.

Of course, it’s not just the seabirds themselves we’ve lost. It’s their poo too.

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“I can tell you seabird shit is not fun to work with. It’s very oily, very smelly and very persistent,” says Bellvé, who “got covered in a lot of bird shit” across several field seasons. The excrement of seabirds provides a nutrient-rich fertiliser, delivered direct to the forests via what Bellvé calls “the Uber Eats of the sea”. Seeing the prior extent of potential seabird poo distribution in his maps hammered home just how important this fertiliser must’ve been to New Zealand’s vegetation, so he sought to figure out just how much poo we’re missing.

“A lot of people gave me shit,” says Bellvé. Shag shit. Fairy prion faeces. Diving petrel doo-doo. Little penguin poo. He collected excrement too. On one occasion, Bellvé laid out a tarp underneath a pied shag roosting tree to collect droppings. He began to scrape the scat off the plastic—it was a good haul—when he felt a wet splatter and saw a yellow mist appear around him. “We had a two-hour drive home with the window down. It was extraordinarily pungent.”

But worth it. Bellvé analysed the chemical composition of different species’ poo, and combined this with population estimates to figure out how much nutrient-laden faeces is shuffled from ocean to land. The results were striking: the poo cycle has shrunk to perhaps an eighth of what it was. It’s also shifted. In the past, he says, “more than one-quarter of the nutrients were going at least 10 kilometres from the shore—far enough that you don’t even have a hint of the coast, unless you’re on a sizeable hill, or you have a bird’s-eye view”.

That dramatic decline in poo is compounded, of course, by the loss of nutrient-rich flotsam that litters seabird breeding sites: eggshells, dead chicks and vomit. Seabird architecture has disappeared as well, with excavated burrow networks no longer churning through the soil. What does this mean for our forests?

There are two nutrients that are key to the growth and reproduction of plants. Nitrogen provides the initial kickstart to an ecosystem, while phosphate keeps it ticking over. “Birds would have supplied New Zealand ecosystems with the major—if not only—source of phosphate to our forest ecosystems,” says professor Amanda Black, a soil scientist at Lincoln University. Black is leading research into the soil ecosystems underpinning kauri forests, and has pinpointed the loss of seabirds—and their phosphate delivery service—as a potential factor behind the decline of kauri.

“The forests have probably run out of juice, and are struggling to recruit seedlings and keep going,” she says, but it’s tricky to know the timescale of changes in the forest, as effects can lag behind losses and be hard to observe.

“No one’s actually done any sort of demographics on these forests, based on the lifecycle of the trees. We could be at the beginning of it all or at the tail end or somewhere in the middle. It’s really difficult to know.”

It’s possible that the absence of seabird poo has enabled the kauri dieback pathogen to spread by affecting the resilience of the soil microbiome. “It could be that seabirds transfer beneficial microbes to the soil that might help confer resilience,” says Black. Her search for clues continues in the forests of Hauturu-o-Toi and Aotea.

What we do know is that seabird guano deposits and seabird-burrowed soils are among 18 “critically endangered” ecosystem types in Aotearoa, according to an analysis led by Manaaki Whenua researchers. We also know that nutrients from seabird colonies wash into coastal environments, boosting the richness and abundance beneath the waves.

Black hopes that understanding seabirds’ role in forest resilience will spur action. “Seabirds are a keystone driver of New Zealand ecosystems—and they have been for millions of years. If that’s not a push to increase conservation of seabirds, then I’m not sure what is.”

Many people, including Willy Ngamoki and his whānau in the Bay of Plenty, are ramping up weed and predator-control efforts to create safe spaces for seabirds and attract them back to their old haunts.

Manawatu would love to see numbers grow enough to restore traditional Kaikōura tītī harvesting, the practice that once upon a time was just part of life for his hapū, but we may never be able to fully restore the immense seabird communities that once enveloped the mainland with a night-time chorus of cackles and roars.

Even in the absence of predators, it can take decades for colonies to re-establish.

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In November 2019, Auckland Council rangers came across an egg sitting outside a hole beneath gnarled tree roots in Tāwharanui Regional Park north of Auckland (a peninsula bounded by a predator-proof fence). They suspected the misplaced egg was the work of a stoat and placed a trail camera to capture the culprit, but on reviewing the footage, they saw feathery seabird bums disappearing into the hole. Seabird scientist Edin Whitehead and volunteer James Ross were dispatched to investigate. Whitehead reached her arm into the burrow, nearly a metre deep, and extracted a dead Cook’s petrel, a seabird that had not bred on the mainland for perhaps a century or more. “It was mixed emotions,” recalls Whitehead. “We found something amazing, but that something amazing was dead.”

But wait. Later that season, two feathery seabird bums were captured on trail cam again, cleaning out the burrow and readying it for the following summer. In November 2020, the Cook’s petrel pair returned, and footage of the birds coming and going in turns indicated they were sharing incubation duties. There was an egg. Two months later, Ross watched the trail cam footage as a downy chick ventured outside the burrow and began flapping its wings. It exercised for about a week, then on March 9, 2021, it fledged.

Westland petrels are among our largest burrowing seabirds, and one of the few still present on the mainland—an estimated 4000 breeding pairs occupy a 16-hectare patch of forest behind Punakaiki.

“We were thrilled,” says Ross. “These birds have come back of their own accord, found a nice patch of forest that’s pretty much pest-free, and are hopefully starting to establish a new population. If you create the right conditions, nature will do what it does.”

The Cook’s petrel pair have returned for two more summers, raising a total of three chicks at that first known mainland breeding site at Tāwharanui. And in 2022, a second mainland site—this one inland, in the Maungahururu Range in Hawke’s Bay—bore another fluffy chick. It’s the tiniest speck on a heatmap, if it even flashes up at all—but it’s a start.

Seeing ghosts: to imagine what the mainland might have been like, look to the clouds of tītī at the Snares/Tine Heke.

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