US skyscrapers kill 600 million -- yes, million -- birds every year

Chicago was the most dangerous city in the USA for migrating birds.

(CNN)Around 600 million birds die every year in the United States after striking tall buildings -- with Chicago, Houston and Dallas being especially deadly, according to research from the Cornell Lab of Ornithology.

Attracted to the artificial light in high-rise blocks, birds can become disorientated and crash into walls -- many of which are made of glass -- suffering injury and often death.
The issue is particularly stark during migratory seasons in spring and fall, when billions of birds pass through the central United States on their way between Canada and Latin America, according to the ornithology lab, which has just issued a list of the most dangerous cities for migrating birds. It estimates that well over half a billion birds are dying in this way every year in America.
Chicago is the most dangerous place for birds during both seasons, closely followed by Houston and Dallas. There, accidents kill birds that have covered thousands of miles on their journeys only to perish in seconds as they collide with glass buildings.
    Kyle Horton is the lead author of the study, published in the journal Frontiers in Ecology and the Environment last week.
    "Chicago, Houston, and Dallas are uniquely positioned in the heart of North America's most trafficked aerial corridors. This, in combination with being some of the largest cities in the US, make them a serious threat to the passage of migrants, regardless of season," he said in a statement posted online by The Cornell Lab of Ornithology.