Early Tuesday morning, Melissa Breyer set out to do her usual volunteer work — collecting the bodies of migratory birds who had died colliding with skyscrapers in downtown Manhattan.

That morning was much worse than usual. In just over an hour, Breyer picked 226 tiny, lifeless bodies off the sidewalks around the World Trade Center. Another 35 had died but fallen onto inaccessible awnings. Thirty were still alive in need of veterinary aid and were transferred to the care of a wild bird rehabilitation center.