Gulls lure birds to high-rise death

briefing: Wildlife

Seagulls in Toronto have learned to lure migrating birds to their deaths by guiding them into skyscrapers, claim researchers.

Like the Cornish wreckers who used to lure ships onto rocks for their cargoes, the gulls dupe their prey into crashing into high glass buildings, which stuns them. The birds then fall to street level, which can kill them, and the gulls eat the remains.

The extraordinary phenomenon, reported today in New Scientist magazine, has been seen in Toronto home of the world's tallest structure, the CN Tower.

While city birds learn to avoid bright lights and reflective glass, thousands of migrating birds die after crashing into the skyscrapers. The exhausted birds are first attracted to the bright lights and then get trapped in the maze of buildings. Usually "some collide with the glass, some drop from exhaustion," said Michael Mesure, of Toronto's Fatal Light Awareness Programme (FLAP), a voluntary group dedicated to rescuing stunned birds.

The gulls started off scavenging dead birds that had been accidentally killed. But, said Mesure, "as more gulls competed for food, some learned to drive birds into collisions".