In the first of a two-part series (the first part of which aired Wednesday) on NPR’s Morning Edition, American Bird Conservancy ornithologist Christine Sheppard described her research into how birds respond to different types of glass. And the motivation behind it: the numbers of birds killed each year in building collisions.

“Our best estimate is 100 million to a billion,” Sheppard said.

“It’s an incredible number,” observed NPR Science Desk Correspondent Christopher Joyce, “and she acknowledges it’s an estimate. But it’s based on reasonable assumptions.”

Reasonable assumptions? Like those used by ABC to “estimate” the number of birds killed each year by cats? Read more