Mass bird deaths rare, not apocalyptic - experts

OSLO (Reuters) - Birds falling out of the sky in the United States and Sweden are freak examples of the kind of mass animal deaths, from beached whales to deluges of frogs, that have unusual but not apocalyptic causes, experts say.

Storms, hail or lightning can kill birds while tornadoes or waterspouts may suck up small fish or frogs and drop them far away. Human causes, such as fireworks, power lines or a collision with a truck, may explain avian deaths.