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Skyscrapers: bird s bane

the brightly lit skyscrapers of North American cities attract migrating birds. But these skyscrapers are also the cause of their death, as every year hundreds die after crashing into them. But in Toronto their prospects are being made worse by local seagulls, which have learnt to guide the birds towards the buildings so that they collide with them. The gulls then feed off the corpses.

While city birds have learnt to avoid bright lights and reflective glass, migrants "are attracted to the light, then get trapped in the maze of the buildings', says Michael Mesure of Toronto's Fatal Light Awareness Programme ( flap ), a volunteer group that rescues dazed birds from around the city's skyscrapers every morning. "Some collide with glass, some drop from exhaustion. But as more gulls competed for food, some learnt to drive birds into collisions.' The gulls use the buildings as "tools' for gathering food, he says, herding the birds like sheep. Daniel Klem of the University of Pennsylvania calculates that lit-up buildings and smokestacks kill 100 million birds a year in North America.