Close this search box.

Bird/Glass Collision Project Wraps Fall 2021 Season with Record Numbers

Every morning between September 7 and October 31, 2021, more than 20 volunteers woke up early to hit the streets of Portland to search for birds that collided with glass windows. This monitoring program began just a year ago, during the fall of 2020, and so we were able to compare seasonal data for the first time.

The Portland monitoring is part of our larger BirdSafe Maine program, which seeks to raise awareness of the problem of bird/glass collisions and provide solutions for homeowners and businesses. It’s estimated that as many as one billion birds die in the U.S. each year from colliding with glass, which can deceive birds by reflecting habitat or by appearing invisible. Learn more about our efforts at our BirdSafe Maine page

Maine Audubon is continually grateful for our partners in this work, the University of Southern Maine (USM), the Portland Society for Architecture, and Avian Haven.

A White-throated Sparrow found in Portland on Sept. 19, 2021

In Portland, volunteers walk a prescribed route through the city from Commercial Street up to Congress and back. We check for birds anywhere on the sidewalk, both in front of buildings we suspect induce more accidents and those that we suspect are safer for birds. The difference, as the science shows, is the amount of glass. Many of Portland’s buildings, such as those that are found in the Old Port, are dominated by brick or stone facades with smaller windows and are less likely to induce bird strikes. Large areas of glass are prevalent elsewhere in Portland, however, especially among newer buildings. It’s those buildings, we found, that cause the most problems for birds. We tested that hypothesis once again this fall, here’s what we found:

Fall 2021 – Portland Route

Volunteers walking the Portland route found 91 individual birds this fall between September 7 and October 31. The major difference between Fall 2020 and Fall 2021 is that we improved our route coverage. In 2020 we had all volunteers walk the same route in the same direction, beginning and ending at Ocean Gateway on Commercial Street. However, we discovered in 2020 that volunteers actually had very little time to find birds on the sidewalk before gulls etc. got to them, so we began in Spring 2021 to encourage volunteers to improve coverage by starting at different locations. 

Lilah and Hazel O’Connor, aged 11 and 8, hold two birds they found while volunteering with their family on Sept. 19, 2021

The 91 individual birds found on the route this fall represented a major increase over the 55 individuals we found on the route last fall. Dr. Chris Maher from USM has once again put together some great slides to help illustrate. Here is a comparison of birds found between this fall and last. The overall pattern matches that of 2020: fairly consistent strikes in September peaking at the end of the month and then tapering off through October as migration wanes. 

Of these birds, most were found dead. A little more than half were found stunned, and some were seen striking buildings but not to the extent of immediate injury. This chart compares all three of our seasons so far.

More than 25 species of birds were found this fall, including Ruby-throated Hummingbird, Yellow-bellied Sapsucker, thrushes, warblers, vireos and sparrows. Common Yellowthroats and White-throated Sparrows were the most commonly-found species.

The BirdSafe team is looking forward to the off-season to refine our strategies, reach out to building owners, plan for the spring session, and continue working to highlight solutions for homeowners and businesses.

Off Route Submissions

An important part of this project is to raise awareness among people all across Maine. Bird strikes are not exclusive to the cities, so encouraging homeowners and businesses to adopt bird safe building practices is important. I encourage anyone to send in bird strikes, and this fall had 62 total submissions, a massive increase over Fall 2020.

This Red-eyed Vireo was found stunned at a residence in Westbrook on Sept. 24, 2021, and transported by Avian Haven.

Reports came in from all over the state: Portland, South Portland, Oquossoc, Freeport, Falmouth, Owl’s Head, Greenville, Auburn, Brunswick, Blue Hill, Sweden, Topsham, Buxton, Westbrook, Farmington, Scarborough, and Swan Island. There was a lot of overlap between species found on vs. off-route, but off-route submissions also included species like Rose-breasted Grosbeak, Blue-headed Vireo, and Black-throated Blue Warbler.

Thank you to the dozens of individuals who shared their sightings with me this fall, and especially to those who considered mitigation measures for the glass windows on their homes. Another special thanks to Avian Haven volunteers here for sharing several species with me they found as part of their efforts.

Additional Efforts

In addition to our efforts on the streets of Portland we are taking a number of other steps to raise awareness of bird strikes around Maine.

Thanks in large part to our partnership with Portland Society for Architecture, who has hosted me for a number of events featuring architects, builders, and others in that world, we are closing in on some glass panel donations for Gilsland Farm. Working with GlasPro and Marvin, we’re aiming to continue our effort to turn our Falmouth Gilsland Farm HQ into a showcase for different bird safe strategies.

We’re also continuing to work with builders working on specific projects to help encourage bird safe architecture and to raise awareness of companies like Simons Architects that are working hard to do the right thing already. One such project is a mid-mountain lodge under construction near the top of Saddleback Mountain.

We’re also improving our stock of bird safe window treatments at the Nature Store at Gilsland Farm, including products from Feather Friendly and CollidEscape

Finally, we’re accepting window strike records at any time. If you find a bird that has struck a window at your home or anywhere, please take photographs and send to Thank you for your help!  

Swainson’s Thrush found in Portland on Sept. 30, 2021