Lost world of birds and frogs: Scientists open a million-year-old cave time capsule in New Zealand, where 12 bird species and four frogs reveal a lost world reshaped by volcanoes and climate long before humans arrived

Imagine discovering a whole lost world tucked away inside a cave, a world no one even knew was there. That’s pretty much what happened near Waitomo on New Zealand’s North Island, where scientists have cracked open a fossil record that rewrites the story of one of Earth’s most unusual bird kingdoms.

According to a study titled ‘The first Early Pleistocene (ca 1 Ma) fossil terrestrial vertebrate fauna from a cave in New Zealand reveals substantial avifaunal turnover in the last million years,’ published in Alcheringa: An Australasian Journal of Paleontology, researchers from Flinders University and Canterbury Museum found that the fossils in a limestone cave are from 12 bird species and four frog species that lived approximately one million years ago.

This is the first time scientists have recovered a large collection of terrestrial vertebrate fossils from this period anywhere in New Zealand, a find that researchers are calling a “missing volume” of the country’s natural history.


A world completely unlike today's New Zealand
The bird community of New Zealand a million years ago was dramatically different from the one that met the first human settlers about 750 years ago. Associate Professor Trevor Worthy, lead author from Flinders University, says this is a newly recognized avifauna for New Zealand, one that humans replaced a million years later.

The cave, now called Moa Eggshell Cave, contained the bones of several remarkable species. These include a now-extinct ancestor of the takahē (a flightless swamphen native to New Zealand) and an ancient pigeon species closely related to Australia’s bronzewing pigeons, which were not around in the million years before humans arrived.

The kākāpō's ancient cousin may have had wings that worked
But the headline find is a newly described parrot species, Strigops insulaborealis, an ancient kākāpō relative. If you’re not familiar with the kākāpō, it’s one of nature’s most improbable birds: the only flightless parrot in the world, the heaviest parrot alive, and critically endangered. As of 2026, there are only 235 known kākāpō in existence, and all of them are on islands free of predators.

The modern kākāpō has powerful legs for climbing and ground travel because it cannot fly. But according to the Alcheringa study, analysis of the fossilized bones of Strigops insulaborealis shows it had significantly weaker legs than its modern relative, suggesting it may not have relied on climbing as much. The ancient bird may have retained some ability to fly, researchers suggest, but they say more research is needed to confirm it.

It’s a tantalizing prospect: that the kākāpō lineage may once have soared through New Zealand’s ancient forests before something forced it to give up flight altogether.

Volcanoes were reshaping New Zealand long before humans arrived
The predominant story of extinction in New Zealand was that of human arrival. And that chapter is real: settlers brought predators, hunted birds, and caused huge damage. But this cave adds a much older chapter that was completely missing.

According to the study, between 33% and 50% of species that lived in this cave went extinct over the million years before humans arrived on the islands. These losses were driven by relatively rapid climate shifts and cataclysmic volcanic eruptions, which repeatedly tore apart habitats and forced ecosystems to rebuild, said co-author Dr Paul Scofield, Senior Curator of Natural History at Canterbury Museum. Changes in forest and shrubland habitats forced a reset in bird populations and were likely a key driver of the evolution of New Zealand’s unique birds.

Volcanic ash that worked like a clock
One reason that this discovery is so scientifically valuable is that the fossils were dated with remarkable precision. The Alcheringa study found that the bones were sealed in between two different layers of volcanic ash in the cave. One layer was from an eruption about 1.55 million years ago, and the other from a massive eruption about 1 million years ago. That geological sandwich neatly brackets everything preserved in between with firm age limits.

According to the study, the younger eruption probably blanketed much of the North Island with meters of ash, most of which was later washed away. But inside the safe confines of the cave, layers were preserved. It was the older ash layer that also held a surprise, making this the oldest known cave on New Zealand's North Island.

Filling the biggest gap in New Zealand's fossil record
The discovery plugs a big gap in the fossil record of ancient New Zealand. Previous excavations at St. Bathans, in Central Otago, had given scientists a snapshot of life in New Zealand 20 to 16 million years ago, but almost nothing was known about the intervening millions of years before the richer fossil record of recent times.

Dr. Scofield summed it up with a line that stuck: “This wasn't a missing chapter in New Zealand's ancient history. It was a missing volume.”

Associate Professor Worthy says these fossils now “provide a critical, missing baseline for New Zealand's natural history” and show that powerful natural forces were shaping the country's wildlife for millions of years before humans arrived.