Image copyright Science Photo Library Image caption 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."

Human cost

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.

The impact of drones is yet to be assessed, but the researchers fear they could be a growing problem.

The scientists say that areas of pristine airspace should be created.

These could be temporary zones, for example to help protect birds on their seasonal migrations, or more permanent areas, put in place over key habitats.

The scientists add that the impact on wildlife needs to be taken into account in the planning stages of major construction projects.

Dr Lambertucci said: "If you know all the species that use that area before you build an airport or a building or a wind farm, you will probably be able to reduce a lot of the conflicts."