Washington: The most ambitious genetic study ever, involving over 200 scientists from across the world and 23 research papers, undertaken on bird evolution has found that almost all modern birds diversified after the dinosaurs became extinct 66 million years ago.
The discovery also gives new details on how birds came to have feathers, flight and song.
To reach this conclusion, an international collaboration of scientists worked for four years to sequence, assemble and compare the full genomes of 48 bird species representing all major branches of modern birds.
"The popular view until now has been that the extraordinary diversity of birds began during the dinosaur age but we found little support for this," said associate professor Simon Ho from the University of Sydney who led a major component of the research.
His research helped confirm that some of the first lineages of modern birds appeared about 100 million years ago but that almost all of the modern groups of birds diversified in a small window of less than 10 million years, just after the dinosaurs were wiped out by an asteroid.
Non-avian dinosaurs did not survive that extinction but avian dinosaurs, what came to be today's birds, did.
Birds fairly quickly - on an evolutionary scale, over several million years - developed into more than 10,000 species.
Another significant finding is that the ancestor of most of the land birds we see today is probably an apex predator that gave rise to raptors, eagles, owls and falcons in rapid succession before leading to land birds such as songbirds and woodpeckers.
"With the demise of the dinosaurs, birds and mammals were able to become more diverse and to occupy all of the niches that had previously been dominated by dinosaurs," Ho added.
"This project generated an unprecedented amount of genomic data for a single group of vertebrates," said Claudio Mello, professor of behavioral neuroscience at the Oregon Health & Science University.
"Our data helped solidify the surprising notion that parrots and songbirds are sister groups in the tree of life of birds, so their shared ability to learn songs - in the case of parrots, human speech sounds - likely had a common origin," Mello added.
"In contrast, songbirdss are separate, so their ability to learn songs - yes, hummingbirds sing and learn how to sing from their parents - arose separately in evolution," the authors said.
Taken as a whole, the papers give science important new insights into the family tree of birds, including the molecular details of the burst of evolution in birds that quickly followed the mass extinction of three-quarters of the Earth's plants and animals.
The consortium of more than 200 scientists is publishing its findings nearly simultaneously this week in 23 papers - eight papers in the journal Science and 15 more in Genome Biology, BMC Genomics and other journals.