Two major studies reveal bird populations in Asia and the US are ‘in crisis.’
The two studies are published in the journals; Science and Biological Conservation.
Lead researcher Dr Ken Rosenberg from the Cornell lab of Ornithology and the American Bird Conservancy says habitat loss driven by human activity is a major factor.
"We knew some species of birds were declining, but we thought the more generalistic birds and those better adapted to human landscapes would be filling in the gaps," Mr Rosenberg said.
"We were pretty startled to see that the more common birds, the everyday backyard birds and generalist species, are suffering some of the biggest losses,” he said.