Far to the southeast of New Zealand's South Island, two remote island groups hold the entire world of a single penguin species, and for the first time someone has counted every nest from above. What the drones revealed is that the species is not one story but two: the small Bounty Islands hold steady while the larger Antipodes have quietly thinned over three decades. In a world that often reduces living things to a single number, the researchers ask that each colony be understood on its own terms, because a comforting average can hide the very place that most needs help.
Erect-Crested Penguin Survey Finds Stable and Collapsing Populations Within One Species
Two states, not one: stable on the Bounty Islands, declining on the Antipodes
Far to the southeast of New Zealand's South Island, two remote island groups hold the entire world of a single penguin species, and for the first time someone has counted every nest from above. What the drones revealed is that the species is not one story but two: the small Bounty Islands hold steady while the larger Antipodes have quietly thinned over three decades. In a world that often reduces living things to a single number, the researchers ask that each colony be understood on its own terms, because a comforting average can hide the very place that most needs help.
Between 2022 and 2024, a team led by Dr. Thomas Mattern of the Tawaki Project flew drones over the Bounty and Antipodes Islands, roughly 800 kilometers southeast of New Zealand's South Island. They photographed and counted every breeding colony of Erect-crested penguins, a species found nowhere else on Earth. It was the first full survey of the whole species, and it overturned an old assumption about where the birds were thriving.
The counts found about 27,800 breeding pairs on the tiny Bounty Islands and about 29,800 on the Antipodes, which are forty times larger and had long been considered the stronghold. The trends told a different story. The Bounty population has held steady for at least a quarter century, while the Antipodes population has dropped by more than 40 percent since 1995.
The causes are tangled. Skuas, native seabirds that prey on eggs and chicks, grow bolder as colonies shrink and lose the protection of numbers. Co-author Dr. Klemens Pütz suggests that the collapse of Eastern Rockhopper penguins on the Antipodes may have pushed skuas toward Erect-crested young. Storms, growing stronger with Southern Ocean warming, trigger landslides that break colonies apart. Birds from the Antipodes also travel far into the Antarctic Polar Frontal Zone after breeding, while Bounty birds stay closer to home in calmer waters.
The team has nicknamed the situation "Schrödinger's Penguin." From afar, everyone assumed one state for the whole species; up close, two were visible at once.
The finding complicates the species' status. The Erect-crested penguin is already listed as Endangered, based on 1970s estimates that Mattern considers inflated. The new data support that label for the Antipodes but not for the Bounty Islands. Averaging the two would produce a rosier Vulnerable ranking, obscuring the Antipodes decline and leaving the Bounty Islands, probably the species' last secure refuge, exposed to industrial fishing. The researchers argue that protection should follow each population's real circumstances, so the box stays open.
Between 2022 and 2024, researchers flew drones over two remote island groups about 800 kilometers southeast of New Zealand's South Island, photographing and counting every breeding colony of Erect-crested penguins. The species breeds nowhere else but the Bounty and Antipodes islands. The result is the first comprehensive survey of the entire species, published in PLOS ONE, and it overturns a long-held assumption about where the birds are doing well.
The survey was led by Dr. Thomas Mattern of the Tawaki Project, which draws on the university's Departments of Zoology and Marine Science. The team worked with the Antarctic Research Trust and the Global Penguin Society, under permits from the New Zealand Department of Conservation. Funding came from the Vontobel Foundation in Switzerland, through the Antarctic Research Trust, and from the Global Penguin Society.
The counts put about 27,800 breeding pairs on the Bounty Islands and about 29,800 on the Antipodes. That is striking because the Bounty Islands cover just 50 hectares, while the Antipodes are 40 times larger and had long been considered the species' stronghold.
The trends diverge even more sharply. Comparing the new counts with historical records back to the mid-1990s, Mattern's team found the Bounty population essentially unchanged for at least 25 years. The Antipodes population has fallen by more than 40 percent since 1995.
The researchers point to several overlapping pressures rather than a single cause. One is the skua, a native subantarctic bird that preys on penguin eggs and chicks. As Antipodes colonies have shrunk, they have lost some of the collective defense that large numbers provide, so predation losses rise and colonies fragment further. Co-author Dr. Klemens Pütz of the Antarctic Research Trust suggests another factor: Eastern Rockhopper penguins suffered a catastrophic collapse in the second half of the 20th century, with similar declines across their Southern Ocean range, likely driven by warming waters. Fewer than 1,000 Rockhopper breeding pairs remain on the Antipodes. As they disappeared, Pütz says, skuas may have turned to Erect-crested eggs and chicks instead.
Storms add to the strain. Increasingly powerful storms, consistent with wider Southern Ocean climate trends, have caused landslides that break up Antipodes breeding colonies and leave birds more vulnerable. Movement at sea may matter too. According to Mattern, Antipodes birds travel considerable distances into the Antarctic Polar Frontal Zone once breeding ends, while Bounty birds stay nearer their nesting grounds, in more sheltered waters that may offer more abundant food.
The team calls the situation "Schrödinger's Penguin." In the physics thought experiment, opening the box settles whether the cat is alive or dead. Here, Mattern says, the reverse happened: from a distance, everyone assumed one answer for the whole species, but looking revealed two states, stable on the Bounty Islands and declining on the Antipodes.
The finding matters for how the species is classified. The Erect-crested penguin is one of only four penguin species listed as Endangered on the IUCN Red List; New Zealand's hoiho, or yellow-eyed penguin, is another. The hoiho has drawn sustained public attention and conservation effort, while the Erect-crested penguin has been relatively overlooked. Its current listing rests on 1970s population estimates that Mattern says were considerably inflated. The new data support Endangered for the Antipodes population but not for the Bounty one.
That creates a dilemma. Averaged across both populations, the global ranking would improve to Vulnerable, masking the severity of the Antipodes decline and downplaying the exposure of the Bounty Islands, likely the species' last secure stronghold, to industrial fishing. Mattern compares a single improved ranking to putting the lid back on the box. The researchers argue that protection should be shaped by each population's circumstances, not by the species' global status alone.
Citazioni salienti
As Rockhoppers disappeared, skuas may have turned to Erect-crested penguin eggs and chicks instead.— Dr. Klemens Pütz, Antarctic Research Trust
A single, ostensibly improved threat ranking is like putting the lid back on Schrödinger's box, trading a convenient illusion for the stronger protection the Bounty Islands population actually needs.— Dr. Thomas Mattern, Tawaki Project
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