According to the US Fish and Wildlife Service, between four and 50 million birds die every year after colliding with communication masts across the USA. But the author of a new study into the phenomenon has found that it isn’t simply the masts’ presence or height that’s the problem, but the colour of their anti-aircraft lighting.

A report due to be published later this year in the Journal of Ecological Application found that during clear nights, night-migrating birds are able to avoid the masts, but in cloudy or stormy weather, many become disorientated and are attracted to the red glow of the masts’ lights. They are believed to circle them until they collide with the mast, its support wires or each other.

Biologist Joelle Gehring of Central Michigan University spent three years studying the impact on avian fatalities when different types of light bulbs were fitted to more than a dozen masts in Wisconsin. She found that non-blinking red lights caused the highest fatalities – 400 birds across 23 species were counted beneath a single mast during one night in spring 2005 – but when white strobe lighting was tested, it resulted in a 71 per cent drop in bird deaths.

The Federal Aviation Administration has now been approached to determine whether alternative lighting would affect pilots’ ability to see the masts.

And a federal court has since ruled that the Federal Communications Commission – the organisation responsible for regulating the US communications industry – must now evaluate the potential adverse effects of masts on migratory birds, following lobbying by the American Bird Conservancy and Earthjustice.

June 2008