By Rebecca MorelleScience Correspondent, BBC News
1 May 2015
There is a growing conflict between animals and humans in the air
"Airspace reserves" should be created to protect wildlife, scientists say.
They warn that growing numbers of skyscrapers, wind turbines, power lines, planes and drones are threatening billions of flying animals.
Researchers in Argentina and Wales have called for airspace zones where human activity is partially or totally restricted to reduce the aerial conflict.
The report is published in the journal Science.
Sergio Lambertucci, from the University of Comahue and the Argentina Research Council (Conicet), said: "Most of the conservation in reserves and national parks is mainly focussed on the ground or more recently on water. None of them have focussed on the airspace."
The skies are becoming increasingly crowded.
Scientists estimate that millions of animals die each year from collisions with tall buildings, power lines and wind turbines.
But the aerial conflict can cause problems for humans too.
The research team, also from Swansea University in Wales, says that bird strikes with planes have killed more than 200 people globally and have damaged thousands of planes.