The wreck of the penguins
Why did hundreds of dead kororā—little blue penguins—wash up on beaches around the country two summers ago? Has their fate got anything to do with the weather? Or has it got something to do with us?
The Otago Peninsula sticks out into the Pacific like a thumb, as if it’s hoping to catch a ride on the Southland current flowing past the coast. Every night, under the gaze of a 155-year-old lighthouse, hundreds of little birds return from the sea. They waddle up Pilots Beach to nests hidden in the scrub, where their chicks are waiting for a meal. Before dawn, they’re off again to forage in the rich waters off the Otago coast.
There, on a clear, warm morning, I meet Hiltrun Ratz, a scientist and conservationist who has devoted much of her life to studying and protecting these birds. She’s employed by the Pukekura Trust, a joint venture between local conservationists and iwi, to look after the kororā at Pilots Beach.
“When I was offered this job, it was like winning Lotto,” she tells me, depositing a pair of plump, squirming penguin chicks back into their nest box. “Biologically speaking, this is probably the most fascinating seabird you can imagine. They’re so flexible. They can just adapt to food conditions out there.”
This breeding season was looking like a record-breaking year for the kororā of Pilots Beach. Then, things started to go wrong.
“It all started with heavy rainfall at the end of November,” says Ratz. “The rivers got all muddy and they made the ocean muddy.”
This wouldn’t normally be a problem, because the Clutha and Taieri rivers are well to the south, but there were persistent north-easterly winds.
“So it brought all that sediment and murkiness closer to the shore, which is where the penguins are feeding. The fish are still there, but the penguins can’t see them.”
Last December, Ratz noticed chicks losing weight, a sign that parents weren’t coming home at night to feed them.
“There were some that came home once a week. Others disappeared for three weeks. No chick can survive that. The parents ought to be coming home every night, especially when they’re little.”
When kororā parents are faced with the choice of starving themselves or starving their chicks, they’ll put their own lives first. They can always have more chicks next year.
Ratz started feeding malnourished chicks, opening up nest boxes every morning to deliver meals while parents were out at sea. This is the second year she has fed chicks through the summer to keep them alive. Now, she’s waiting for the return of the first year’s chicks, which are microchipped, to breed.
“The champagne will come out,” she laughs. “It’ll be very satisfying because I am convinced that every penguin chick I fed last season or this season would have died without me.”
Two summers ago, New Zealand experienced its most extreme marine heatwave in almost a century. Seas reached temperatures six degrees higher than average, and hundreds of kororā washed up dead along coasts in the north. Autopsies showed the birds had starved, their internal organs wasted as their tiny bodies began to consume themselves.
The heatwave was caused by the two major patterns driving New Zealand’s weather: the El Niño-Southern Oscillation (ENSO), a mass of air moving back and forth in the tropics, and the Southern Annular Mode (SAM), a ring of westerly winds swirling around Antarctica. Both patterns flip between different states at random: ENSO see-saws between El Niño and La Niña conditions, while over Antarctica, the ring of westerly winds expands and contracts. When the westerlies shrink towards the South Pole, known as the SAM positive phase, this results in long, still days and lots of sun for New Zealand, warming the upper layer of seawater. That’s what happened two summers ago: a SAM positive phase coincided with a moderate La Niña, which also causes warmer waters, compounding its effect.
Big penguin wrecks in the north of New Zealand often coincide with La Niña conditions, says Department of Conservation scientist Graeme Taylor, because La Niña also brings persistent easterly winds that drive the penguins’ bodies ashore.
“The penguins struggle to find food in those years and often the chicks depart in poorer condition,” he says. “But the fact that they get seen in such big numbers is just simply because they are coming back onto the beaches.
“Every year, a certain proportion of the chicks don’t make it, but in most years we don’t see them—they drift away into the ocean. So La Niña means you’re more likely to see them. But also, there probably are more dying.”
Meteorologists have noted a steady increase in the number of SAM positive phases over the past few decades, but whether this is part of a natural, long-term cycle is unclear. A 2019 paper by NIWA oceanographer Phil Sutton showed that the oceans around New Zealand have detectably warmed since the early 1980s.
While the link between warm seas and penguin deaths seems obvious, it isn’t—penguin wrecks similar to those of the 2017-2018 summer have been recorded for decades. They seem to be natural if occasional events that occur when unfavourable conditions align to disrupt the chicks’ path to adulthood.
Whether warmer waters affect kororā is a separate question—and keeping a closer eye on penguins in the north is the first step in finding the answer.
“It is pretty fundamental to get a handle on the number of birds nesting up there,” says Taylor. “All the climate-change models are indicating that the oceans are going to get warmer over time. The northern end of the country is going to get warmer quicker than the southern end, so it’s pretty obvious that if there’s going to be an impact on penguins, it’s going to start at the top end.”
Although kororā are a familiar sight, bobbing in harbours and bays around the country, what they get up to out at sea remains a mystery. The smallest of the world’s 18 penguin species, they’re found all around New Zealand, as well as southern Australia. But there is only one long-term study on the birds in New Zealand—a 25-year research project tracking the colony at Ōamaru.
“We don’t have a lot of information or understanding of the species,” says penguin biologist Thomas Mattern. “Mostly we can just come up with conjecture.”
Of the three penguin species that breed on mainland New Zealand, only kororā are familiar to most people on a first-hand basis. They’ll nest in any kind of nook or cranny: beneath logs, amid scrub, in caves, under houses, inside gumboots, and below boardwalks. They readily adapt the human environment for their own purposes, despite the danger this poses to them.
Mattern, who is based at the University of Otago, works mostly with hoiho and tawaki—yellow-eyed penguins and Fiordland crested penguins—but he’s just taken up a position at the NZ Penguin Initiative, which is funded by the T/Gear Charitable Trust, a major supporter of bird research in New Zealand.
“One of the tasks I have in the next three years is to try to reach out to all the little penguin communities in New Zealand, to see where we can find some common ground and how we can combine our efforts to get a better idea of what’s going on with little penguins.
“There’s not a lot of research happening, certainly not in a concerted fashion. There are student projects happening here and there, but they’re like five pieces in a thousand-piece jigsaw.
“We don’t even know how many there are. We have no clue.”
In Australia, the birds have been studied for four decades under a research programme at Phillip Island, near Melbourne. The island is home to 32,000 breeding pairs, and they are a major visitor attraction. Tourist dollars fund studies into the birds’ biology and behaviour. The hope is that this will take place at Pilots Beach, too.
If we knew what kororā are eating, and where they are foraging, that could help us to understand how healthy the marine environment is, says University of Auckland scientist Brendon Dunphy.
So far, sporadic tracking studies have found that kororā at Ōamaru travel up to 35 kilometres offshore to forage during the breeding season, when they require the most food. Penguins in the Marlborough Sounds, however, travel much further while they’re incubating eggs, swimming right up into the Taranaki Bight to feed—a round trip of more than 170 kilometres.
Dunphy and his students are researching several seabird species, including kororā, to try to get a clearer picture of marine life in the Hauraki Gulf and beyond.
“What we’re trying to do is recruit different species to be ocean indicators for us,” he tells me. “Something like a shearwater is going down to the polar fronts, whereas penguins tend to be quite local.”
Because penguins are tied to land during the breeding season, they can be more easily studied than other marine species.
“We’re putting GPS loggers on them,”says Dunphy, “with the view that they could tell us something about what’s going on with the fisheries, ocean conditions, prey abundance, all those indicators we’re looking for.
“At the moment, there’s very warm water temperatures around, so we’re trying to understand what’s the impact of that on them.”
One of Dunphy’s masters students, Kerry Lukies, tracked penguins from the Hen and Chicken Islands, off Northland. Her early results were a surprise—she expected the penguins to prefer the clearer waters around the outer islands for foraging, but instead they headed straight for the muddy, boat-congested waters around the Whangarei river mouth.
Kororā may head for river mouths to take advantage of the high amount of nutrients running off the land, which fuel productive ecosystems, but this behaviour makes them vulnerable to increases in sediment after heavy rainfall.
Philippa Agnew has been looking at the impact of spring and summer storms on the breeding success of kororā at Ōamaru. Stormy years are terrible for the colony, she says.
“The parents tend to stay away from the colony, which during the winter isn’t such a big deal, but during the breeding season, we see nests and chicks abandoned.”
Last year, Agnew watched major storms hit the coast during November—the first time she’d seen such events at that time of year.
“When it was all happening,” she tells me, “I went and had a chat to a commercial fisher, and they were really struggling as well.
“They couldn’t even find the fish let alone catch it—they were having to head way off near the 12-nautical-mile limit, so it just shows me it’s not just the little penguins that suffer during those events—it’s right through the food chain.”
Agnew and other scientists are concerned about storms becoming more frequent, as climate-change models predict.
“In the 25 years of data that we have, the majority of the storm events have been in the most recent years. It’s become more and more regular in the past five or six years.”
Despite a disastrous December, the Ōamaru colony managed to fledge around 400 chicks, thanks to an early start to the breeding season. The penguins’ flexibility in timing their breeding may help them to ride changing ocean conditions better than many other marine species.
“They can start breeding as early as May,” says Hiltrun Ratz.
“But first clutches can also appear as late as October. It’s the female that decides. Once a month through winter she goes, ‘Am I fat enough? Is there enough food out there? What are the neighbours doing?’”
If conditions aren’t right, says Ratz, the birds will disappear for another three weeks before returning to reassess the situation.
“Other species are less flexible,” she tells me.
By contrast, hoiho always lay their eggs at around the same time every year, regardless of sea conditions—and the species is facing extinction on mainland New Zealand.
Kororā are not only flexible in their breeding strategies, but also in their diet. Studies have shown that in different parts of the country, they consume radically different food, from squid to various kinds of small fish, and that this diet also varies greatly from year to year.
But some prey species are better for kororā than others—and scientists have observed how fluctuations in sea conditions can lead to good and bad years for kororā, just as they do for hoiho.
Earlier this year, another marine heatwave struck. Dunedin sweltered through a summer that caused sea conditions at least two degrees warmer than average.
In Otago and Southland, hoiho chicks starved, as parents returned from the sea without enough food to sustain them.
Over the summer, I was filming with NHNZ (formerly Natural History New Zealand) for a television series called Wildlife Rescue. Rangers and conservationists lifted malnourished hoiho chicks from nests and took them to Dunedin’s Wildlife Hospital and other rehabilitation facilities, where the chicks were hand-fed until they fledged, gaining their seagoing feathers.
Some days, the Wildlife Hospital was crowded to bursting as vets and volunteers struggled to keep up with the number of birds. It felt like a triage centre for a species-level disaster.
Scientists such as Mattern are trying to unravel exactly what is going on, but overfishing and warming seas are considered top of the suspect list. Mattern’s research shows that warmer seas are bad news for hoiho, as their breeding success plummets in these years.
When seas are warm, he says, the fish that hoiho rely on for food move out into deeper, cooler waters, and sometimes don’t even spawn at all. Warm waters also become increasingly stratified, which means that cool, nutrient-rich waters from the deep don’t mix as easily with the surface waters, leading to fewer species in the upper layers, where penguins feed.
Similarly, there is a clear link between warm winter sea temperatures in the Otago region and kororā breeding success, says biologist Chris Lalas.
“It’s not so much about the amount of food penguins can find, but about the type of food they have available to them,” he says.
Kororā along the Otago coast prefer a small, oily fish called slender sprats. These fish spawn in winter and live for no more than two years. But during warm winter sea conditions, says Lalas, sprats don’t spawn well. That means the following year there are fewer sprats, so kororā are forced to shift their focus to other prey species.
In Otago they switch to red cod, a much larger fish that can grow up to 60 centimetres. Kororā can tackle only juvenile cod, which are lower in oil content than adult fish. As a result, the penguins don’t do as well in these years.
Last summer’s marine heatwave didn’t cause a repeat of the previous year’s penguin wrecks. Then again, last summer involved mild El Niño conditions, not the La Niña breezes that wash penguin bodies to shore. Were kororā affected out at sea—and we just didn’t know?
The list of things we don’t know about kororā is long. But some aspects of the penguins’ lives and deaths are clear, says Lalas, and we should be acting on those.
“In terms of conservation of little penguins, we know everything we need to know,” he tells me.
Many of the researchers I talk to believe kororā numbers are decreasing around the country, and it isn’t a mystery why.
“Little penguins are declining along coastlines that have people,” says John Cockrem, a scientist at Massey University. “A significant reason for the decline is disturbance, predation and attacks by dogs.
“Climate change may well have big effects in the future, whereas dogs killing penguins is not out in the future, that’s right now. It happens regularly all around our coastlines.”
Predation and disturbance on land are key impediments to little penguin breeding success, says Kerry-Jayne Wilson, head of the West Coast Blue Penguin Trust. Where those impacts are reduced, the penguins do well.
“At Ōamaru and also probably parts of Otago Peninsula, we’ve had this huge increase,” she says. “But those are in strictly protected areas.”
The same is true up north, says Karen Baird, a Forest and Bird seabird specialist who is heavily involved in kororā conservation.
“We know that on predator-free islands in the Hauraki Gulf, penguins do really well,” she tells me, “and that on the mainland they do really badly.”
Baird has witnessed a steady decline in kororā numbers at one of her local haunts, Ti Point, north-east of Warkworth.
“In the old days, there would have been lots of penguins coming in to nest in that area but I don’t think I’ve seen a penguin there in many, many years.
“We know that our dogs, our coastal development and our predators are bad for productivity, so let’s deal with those issues.”
While researchers search for answers to the many questions about the lives and deaths of kororā, there’s plenty that can be done to assist and protect them in the meantime.
“We don’t need more information,” says Baird. “We just need to get on with it.”