A cave in New Zealand preserved a lost world from a million years ago — ancient parrots, giant flightless rails and a bird community reshaped by supereruptions and Ice Age climate swings long before humans ever reached the islands

Moa eggshell scattered across the floor is how the cave got its name, and it turned out to be the least interesting thing in there.

Moa Eggshell Cave sits near Waitomo on New Zealand’s North Island, roughly 280 metres above the stream that eventually sliced the old cave in two and exposed its buried sediment. Beneath that eggshell, in a layer nobody had reason to sieve until recently, lay a bird community with no modern equivalent anywhere: an early parrot, a giant flightless rail, a pigeon with Australian cousins, and enough absences to suggest the place was emptied and restocked long before people arrived.

How volcanic ash dated the bones

A haul of twenty-one usable bone fragments isn’t much to work with. What made them valuable was the packaging.

Those bones sat between two layers of volcanic ash whose ages were already nailed down. Eroded remnants of the Ngaroma ignimbrite, about 1.55 million years old, still cling to the roof and walls. Above the fossils lies a thick band of ash washed in from the Kidnappers eruption, roughly one million years old. A stalagmite growing on top of the sediment, dated to 535,000 years, closes the timeline from the other end. The full sequence is set out in a paper published in Alcheringa: An Australasian Journal of Palaeontology by a team led by Trevor Worthy of Flinders University with Paul Scofield of Canterbury Museum.

Fossil deposits with hard brackets at both ends are rare. The same ash on the walls makes this the oldest cave yet recognised on the North Island.

A parrot with weaker legs

Twelve bird taxa came out of the deposit, two of them new to science. First up is Strigops insulaborealis, an early relative of the kākāpō, the heavy nocturnal parrot that survives today only on predator-free islands and sanctuaries.

Its foot bones are the giveaway. Modern kākāpō have powerful legs for climbing and walking. This older bird’s legs were weaker, which hints it spent less time hauling itself up trees and may still have kept some capacity for flight. Worthy’s team is cautious on that point, and rightly so. A handful of bones from one cave can only suggest when the lineage lost flight. Confirming it will take more material.

A rail named after a fence

The second new species, Porphyrio claytongreenei, is a large flightless rail, and its name honours Warren Clayton-Greene, the landowner who fenced the site to keep goats out and helped haul gear up to the dig. It belongs with the living takahē and the extinct moho, the North Island takahē known only from bones and a single disputed specimen. The authors float the possibility that it was ancestral to both, with the two lines splitting once Cook Strait separated the islands.

A third bird was a pigeon related to the Australian bronzewings, the first of its kind ever recovered from New Zealand’s fossil record, per coverage of the dig.

Frogs that barely changed

Four species of native frog showed up in the same layer, all in the genus Leiopelma, and all recognisable as the frogs still hopping around New Zealand today. Birds churned. Frogs sat tight. Why one group turned over while the other held steady is not resolved in the paper, though small damp animals living in leaf litter plausibly ride out upheaval better than large birds tied to a particular kind of forest.

What reshuffled the forest

“The shifting forest and shrubland habitats forced a reset of the bird populations,” Scofield said when the work was announced in January.

Two forces are in the frame. Glacial and interglacial swings grew sharper through the Early Pleistocene, dragging forest and shrubland back and forth across the landscape. Then there was the volcano. The Kidnappers eruption came from the Mangakino volcanic centre and moved something like 1,200 cubic kilometres of magma, laying down what geologists rate as the most widespread ignimbrite sheet on the planet, tens of thousands of square kilometres of the North Island under ash.

Scofield and his colleagues think that upheaval did more than empty out the forest. In comments to Discover, he credited it with helping drive the evolutionary diversification of the region’s birds as well.

Between a third and a half of the bird species recovered here appear at no younger fossil site in the country. Worthy’s team consider this an entirely separate community of birds from the one people encountered on arrival roughly a million years later. Those humans landed about 750 years ago, and had nothing to do with any of it.

Where that leaves the kākāpō

One lineage in the cave made it all the way through: the supereruption, the ice-age reshuffling, whatever happened to the eleven bird species alongside it. It then nearly went extinct anyway, undone across a few generations by cats, stoats and rats, the sort of threat no volcano ever managed.

Last week the Department of Conservation put the official kākāpō population at a recovery-era high of 325 birds, after ninety chicks from the 2026 breeding season passed the 150-day mark and joined the tally. The programme started in 1995 with 51. Operations manager Deidre Vercoe called it a record season while noting there is still a long road ahead.

Most of those chicks will be named in February and March. A few will not, which the department frames as a first small step towards letting kākāpō be a wild bird again rather than a managed one.