Nearly half of all bird species are at risk, with drastic declines in populations.
The main threats come from the loss of natural habitats and the overexploitation of species, while climate change has been identified as an emerging cause.
This is indicated by the study published in the Annual Review of Environment and Resources, led by the Metropolitan University of Manchester, in the United Kingdom.
Since birds are very sensitive indicators of environmental health, their decline is a sign of much greater biodiversity loss.
"We are seeing the first signs of a new wave of extinctions," says study coordinator Alexander Lees, who works between Manchester Metropolitan University and American Cornell University.
"Globally, avian diversity reaches its peak in the tropics - continues Lees - and it is there that we also find the greatest number of threatened species".
The researchers drew on data from the International Union for Conservation of Nature's (IUCN) Red List, the most comprehensive inventory of species extinction risk globally.
Among the 11 thousand bird species, 48% are seriously threatened, 39% are stable, 6% show an increase and the situation is unknown for the remaining 7%.
Despite everything, the researchers say there is still hope for bird conservation efforts, but a marked change of course is needed.
"The fate of bird populations depends heavily on stopping habitat loss", concludes Lees: "we must try to reduce the human footprint on the natural world."
