Fossil footprints are the oldest traces of birds in Australia

A set of fossilised footprints found in Australia, which date from over 120 million years ago, are the oldest traces of birds in the southern continents.

The earliest birds evolved from theropod dinosaurs about 150 million years ago. But fossil evidence for birds in the Jurassic and Cretaceous periods is extremely rare. “The further back in time, there is less chance of delicate bird skeletons being preserved,” says Julian Hume at the Natural History Museum in London.

This is especially true for birds that lived in Gondwana, an enormous land mass that later broke up to form South America, Africa, Antarctica, Australia, Arabia and the Indian subcontinent.

Previously, the oldest evidence for birds in Gondwana was a wishbone and a feather found in south-east Australia, dating back to roughly 118 million years ago.

Now, Anthony Martin at Emory University in Atlanta, Georgia, and his colleagues have found bird tracks that were made at least 2 million years earlier.

During surveys of the fossil-rich Wonthaggi Formation in Victoria, Australia, the team stumbled across marks in the ground. “I realised they were bird tracks, which was very exciting,” says Martin. “I knew these must be the oldest bird tracks found in Australia and the southern hemisphere,” he says, as the rocks in the formation date back to between 129 and 120 million years ago.

The team found a total of 27 footprints, which have a variety of shapes and measure between 7 and 14 centimetres, suggesting they were made by different types of birds of varying ages.

In the Cretaceous period, the Wonthaggi was much closer to the south pole than it is today. But Earth was also around 10°C warmer than now, so the climate would have been similar to places such as the UK, with pleasant summers and colder winters, says Martin.

The footprints appear in multiple layers of rock representing different times. Because the region would have been cold and dark in the winter, the researchers think the birds didn’t stay there all year round, but stopped there on a migration route every year. “They probably felt quite at home there,” says Martin.

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“Any evidence of a fossil record, albeit the preservation of bird footprints, is of real significance in the world of avian palaeontology,” says Hume.