It's well-known that birds frequently mistake windows for unobstructed passageways and fly into them, often fatally. But, perhaps unsurprisingly, they do so a lot in New York City—and the problem has gotten very bad in recent days:

Hundreds of birds migrating through New York City this week died after crashing into the city's glass towers, a mass casualty event spotlighted by a New York City Audubon volunteer's tweets showing the World Trade Center littered with bird carcasses.

This week's avian death toll was particularly high, but bird strikes on Manhattan skyscrapers are a persistent problem that NYC Audubon has documented for years, said Kaitlyn Parkins, the group's associate director of conservation and science.

Stormy weather Monday night into Tuesday contributed to the deaths, she said.

"We had a big storm and sort of weird weather and lots of birds, and that's sort of the perfect combination that can lead to bird-window collisions," Parkins said.

Video of one volunteer picking up bird carcasses on the sidewalk of the World Trade Center highlighted the grim extent of the problem:

Experts state that turning off lights at night can help prevent migrating birds from becoming disoriented and slamming into windows. So, you know, any tenants of New York City skyscrapers that are reading this: Please turn off your office light at night.

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