A tiny fossil suggests that borebirds once lived in ancient New Zealand – new research

Much of our knowledge of New Zealand’s prehistoric bird diversity comes from long-lost species with large numbers of bones that can be studied by eye. But the bones of many birds are so small that we can barely see their features without a microscope.

About 14 to 19 million years ago, in the Miocene epoch, the remains of thousands of birds were preserved in and around the vast Lake Manoharikia in present-day Central Otago.

We know a lot about some of the larger lake birds like ducks. But we have less information about highly diverse passerines such as small birds, including songbirds. Modern species in this group include the te ī and the tohu/siluris.

The minute bones of passersby are difficult to find in the field, and only come to light after hours of hard work under a microscope. But technologies like micro-CT scanning are now helping to reveal its secrets.

Our new research adds a quirky new passerby to Aotearoa’s fossil record and shows just how unique its ancient biodiversity was. New species appear in the bowerbird family of songbirds, which are not present in New Zealand today.

Made famous by Sir David Attenborough’s nature documentaries, bowerbirds are known for their extensive courtship behavior and the efforts of males to decorate bowers with colorful fruit or leaves to attract mates. These conspicuous males are often brightly colored, while the females are duller.

Until now, borebirds and their fossil relatives have only been found in Australia and New Guinea.

St. Bath’s Bowerbird

Among all the small bones found at the St. Bathens fossil site, a curious foot bone stood out. When we compared the digital models of the fossil to a large number of other passerines, it evoked all the characteristics of a bored bird. But it was much smaller and more slender than living borebirds.

His name is Avipertides gracilisGraceful from a lost age.

The size of Avipertides gracilis This would make it the smallest known borer bird. Most living borebirds are chunky, weighing anywhere from 62 to 265 grams and spend time on the ground and in the forest canopy.

The New Zealand bowerbird weighed about 33 grams, similar to the korimaku/bellbird but with longer feet.

Our analysis showed that the St. Bathans bowerbird foot was similar to a group known for building walk-through avenue bowers, such as the brightly colored flame borerbird.

We can only speculate about its plumage and behavior, but Avipertides gracilis Elaborate displays may also have been performed to attract mates.

The St. Bath’s bowerbird joins other New Zealand passerines with an ancient history including the hawaii, kaka, piupio and mohua, whose ancestors flew across the ocean to Zealandia millions of years ago.

The Saint Bathin’ Bowerbird lived far from its relatives in warmer Australia and New Guinea. If it was a fruit-eater, it may have been poorly equipped for temperatures that began to drop dramatically about 14 million years ago and caused a decline in plant diversity. Finally, it may suffer from climate change.

Conservation Paleobiology

Fossils such as the St. Bathin’s Bowerbird as well as genetic research are revealing the evolutionary story of New Zealand’s birds, with extinctions and repeated colonizations over geological time.

For example, prehistoric Shelducks colonized ancient Zealandia, only for them to become extinct. About 2 million years ago, the Shelduck, ancestors of the Putangitangi/Paradise, repopulated New Zealand.

The same is true for the ancient passerine relatives of magpies, which became extinct after the Miocene. But unlike the native Shelducks, modern magpies/Australian magpies were introduced by Europeans in the 1860s.

Some researchers have suggested that these long-lived species muddy the concept of what is native or introduced to New Zealand, using magpies as examples.

Even though ancient magpie relatives once lived in Zealandia, that doesn’t mean their living cousins ​​belong in modern ecosystems. This thinking can undermine conservation management and lead to further degradation of ecosystems by invasive species.

Before the Southern Alps rose to form the backbone of the South Island, St. Bath’s Wonderland was a Zealandia. Lake Manoharikia was home to many plants and animals, including crocodiles and turtles, which are very different from today. It makes no sense to regard these ancient animals as indigenous to modern Aotearoa.

New discoveries like the St. Bathin’s bowerbird provide a fascinating insight into New Zealand’s biological heritage. Let’s celebrate these discoveries as clues to the past and not use them to undermine the ongoing fight to protect the country’s unique resident plants and animals.

We thank Daniel Field and Alex Brown, co-authors on our paper, Sasha Votyakova, for artist reconstructions, the landowners of St. Bataan for access to their land, Jean-Claude Stahl for producing fossil photographs, and the numerous field workers who assisted with our excavations.

This article is reprinted from The Conversation under a Creative Commons license. Read the original article.