Maine Audubon says this fall was the second deadliest on record for birds crashing into glass windows in the Portland area. The group began tracking collisions five years ago.
Outreach manager Nick Lund said volunteers with the group's BirdSafe program found 158 dead or injured birds.
"And that represents just a very small number of the overall birds that we know strike in Portland," he said.
Lund said it's unclear what made this year so deadly for migrating birds, but added that there were some signs of progress.
"We worked over the summer with the WEX company to put bird safe film in the back corner of their building, which has been a real hot spot for years for us," he said. "And we were really heartened to see no dead birds back there this fall."
Lund says his group wants to work with more companies and homeowners across Maine to make their windows more bird safe.
