Hundreds of migrating songbirds crash into New York City skyscrapers

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 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.

"It seems that the storm might have brought the birds in lower than they would have otherwise have been, or just disoriented them," Parkins added. "The effects of nocturnal light on birds is also quite strong, especially when it's a cloudy night."

Volunteers with NYC Audubon document bird deaths at high-risk spots during the spring and fall migrations.

Melissa Breyer, the volunteer who tweeted about finding nearly 300 birds on sidewalks surrounding the new World Trade Center towers, said the experience was "overwhelming."