SerpApi.Org
Buried beneath a limestone cave on New Zealand’s North Island, sediment sandwiched between two bands of volcanic ash has preserved the bones of animals dead for more than a million years. Researchers who excavated the site, known as Moa Eggshell Cave, have now described 16 species previously unknown from that period: 12 extinct birds and four extinct frogs. Several of the bird species had never been documented by science before.
The cave takes its name from what first drew scientific attention to it: moa eggshell fragments scattered across its floor, remnants of the giant flightless birds that dominated New Zealand’s forests until a few hundred years ago. What the team found in the deeper sediment was far older and, in terms of the fossil record, considerably more significant.
The study was published in the Journal of Palaeontology and led by Trevor Worthy, associate professor at Flinders University, with co-authorship from Paul Scofield, senior curator of natural history at Canterbury Museum. Together, the team argues the find represents not a missing chapter in New Zealand’s natural history, but a missing volume.
A Window Sealed by Two Volcanic Eruptions
The fossils owe their survival to a specific geological sequence. Two separate volcanic eruptions deposited ash layers inside the cave at different points in deep time: the first roughly 1.55 million years ago, the second approximately 1 million years ago. The bones found between those two ash bands date to somewhere in the range of 1 to 1.5 million years old, placing them in a period that had previously yielded almost nothing in New Zealand’s fossil record.
Researchers already had a reasonable picture of the country’s wildlife from around 18 to 20 million years ago, drawn from older deposits elsewhere. They also knew the more recent past, roughly the last thousand years, from bones preserved in coastal caves and dunes. The vast middle stretch, covering millions of years of ecological change driven by eruptions and climate shifts, had remained almost entirely undocumented.
The cave environment itself mattered. Sheltered from the elements and sealed by successive ash layers, the bones were protected from the disturbance that would ordinarily have destroyed them across such a long timescale. Worthy described the collection as “a newly recognised avifauna for New Zealand,” noting that the find “suggests our ancient forests were once home to a diverse group of birds that did not survive the next million years.”
The Ancestor of the Kākāpō May Have Been Able to Fly
Among the 12 extinct bird species, one stands out for what it implies about a species still alive today. Researchers identified a new parrot named Strigops insulaborealis, an ancient relative of the modern kākāpō, the critically endangered, ground-dwelling, flightless parrot that has become one of New Zealand’s most recognized conservation cases. The two birds are clearly related, but their skeletons tell different stories about how they moved.
The modern kākāpō has powerful, muscular legs suited for climbing trees and covering ground on foot. Its million-year-old ancestor had comparatively weaker legs, pointing to less time spent on the ground. That difference raises the possibility that Strigops insulaborealis could fly, an ability the kākāpō lineage appears to have lost somewhere between then and now. The researchers note that more study is needed to confirm this, but the structural distinction alone reframes the evolutionary history of one of the world’s most studied endangered birds.
The cave also preserved bones from an extinct ancestor of the modern takahē, another large flightless bird that survives today only through intensive conservation management. A third find was an extinct species of pigeon closely related to the Australian bronzewing pigeons, a group not previously known to have lived in New Zealand.
Extinction Before Humans Arrived
The study’s broader findings concern the scale of pre-human extinction on the North Island. The researchers estimate that between 33 and 50 percent of all bird species present during the period represented by the fossils went extinct during the million years before humans reached New Zealand. The drivers were not hunting or habitat clearance, but repeated volcanic eruptions, rapid climate shifts, and the cycles of forest growth and collapse that followed each disturbance.
Scofield described how those forces played out across generations of wildlife. “The shifting forest and shrubland habitats forced a reset of the bird populations,” he said. “We believe this was a major driver for the evolutionary diversification of birds and other fauna in the North Island.” Each reset cleared out some lineages and opened conditions for new ones to evolve in their place.
Worthy noted that the study shifts how scientists should think about New Zealand extinction more broadly. “For decades, the extinction of New Zealand’s birds was viewed primarily through the lens of human arrival 750 years ago,” he said. “This study proves that natural forces like super volcanoes and dramatic climate shifts were already sculpting the unique identity of our wildlife over a million years ago.”
What the Find Adds to the Fossil Record
The Moa Eggshell Cave material fills an interval that had no meaningful fossil documentation. Before this study, the period between roughly 1 and 1.5 million years ago was effectively invisible in New Zealand’s paleontological record, making it difficult to connect the fauna known from older deposits to the wildlife that greeted the first human settlers.
Scofield put the significance of that gap plainly. “This wasn’t a missing chapter in New Zealand’s ancient history,” he said. “It was a missing volume.” The new collection provides a physical baseline for the North Island’s Pleistocene fauna, a period that had previously existed only as inference drawn from sites with different ages and preservation conditions.
The animals that survived into the human era were not a stable community that had persisted unchanged across deep time. They were the result of repeated disruption, survival, and change across a landscape shaped by prehistoric extinction long before the first settlers arrived.
