Birds survived the big asteroid because they couldn't fly
Only later did they evolve the power of flight, new research finds
The common ancestor of all living birds was a flightless, partridge-like creature which only survived the asteroid strike that wiped out the dinosaurs because it lived on the ground, scientists have concluded.
Birds had to rediscover flight all over again after tree-dwelling varieties were killed off 66 million years ago alongside huge predators like Tyrannosaurus rex.
An international team of scientists studied the fossil record and found that the asteroid strike caused global deforestation and the extinction of most flowering plants, destroying the habitats of all most all birds.
Only those on the ground were able to survive, and it would be thousands of years before any evolved flight and took to the trees again.
“We drew on a variety of approaches to stitch this story together,” said lead author Dr Daniel Field of the Milner Centre for Evolution at the University of Bath.
“We concluded that the devastation of forests in the aftermath of the asteroid impact explains why tree-dwelling birds failed to survive across this extinction event.
“The ancestors of modern tree-dwelling birds did not move into the trees until forests had recovered from the extinction-causing asteroid.”
The 10 to 14km-wide meteor, which may have been an asteroid or comet, struck the Earth off the coast of Mexico releasing a million times more energy than the largest atomic bomb.
Hot debris raining from the sky is thought to have triggered global wildfires immediately after the impact.
Dr Regan Dunn, a member of the team from the Field Museum in Chicago, US, said: “Perching birds went extinct because there were no more perches.
“Looking at the fossil record, at plants and birds, there are multiple lines of evidence suggesting that the forest canopies collapsed.”
Paleobotanist Dr Antoine Bercovici from the Smithsonian Institution analysed the plant fossil record before and after the asteroid strike.
He said: “The recovery of canopy-forming trees such as palms and pines happened much later, which coincides with the evolution and explosion of diversity of tree-dwelling birds.”
The researchers found that once the forests had recovered, birds began to adapt to living in trees, acquiring shorter legs than their ground-dwelling ancestors and various specialisations for perching on branches.
Dr Field added: “Only a handful of ancestral bird lineages succeeded in surviving the mass extinction event 66-million-years-ago, and all of today’s amazing living bird diversity can be traced to these ancient survivors.
“We are working hard to shed new light on this murky portion of the fossil record, which promises to tell us a lot about how birds and other animal groups survived – then thrived – following the extinction of T.rex and triceratops.”
• The research was published in Current Biology
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