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Collision Monitoring

What is  Monitoring

Collision monitoring involves carefully searching for, identifying and counting any birds that have been killed or injured by colliding with buildings in a particular area. Bird-window collision monitoring studies are most often conducted during periods when birds are migrating through an area, especially in urban areas where collisions usually occur most often during migratory periods. But monitoring studies can also be conducted at other times of the year, especially in areas where breeding or wintering bird populations may be at risk



Much of what we know about the problem of bird-window collisions has been learned through monitoring. Monitoring has been used to determine what species collide with buildings, the number of individuals involved, the times of the year when collisions occur, the times of the day when collisions occur, what parts of a building birds are colliding with, and other things.


Monitoring data can be very useful in determining how a building can be modified physically or operationally in ways that will reduce or prevent bird-window collisions. And when data from multiple monitoring studies has been combined it has helped us to understand which species of birds are most vulnerable to window collisions and how many individual birds are killed overall by window collisions each year.

Monitoring in Philly

In Philadelphia monitoring performed by Audubon has indicated that large numbers of migratory birds collide with buildings of all heights in the downtown section of the city during the spring and fall because of the effects that artificial lights on at night (ALAN) and reflective and transparent glass can have on birds that migrate at night. Data have shown that birds regularly collide with residential, industrial and commercial buildings in all other parts of Philadelphia at all times of the year. Monitoring in Philadelphia has also indicated that up to 1000 birds can collide with buildings in just a small (3-4) square block section of the downtown area annually. But not enough sections of Philadelphia county have been monitored to date to determine how many bird window collisions occur throughout the entire county each year. One of the goals of Bird Safe Philly’s monitoring efforts will be to gather monitoring data from as many parts of the county as possible in order to improve our understanding of how bird collisions occur in different parts of the county, and how many collisions occur overall in the county each year. Stay tuned for more updates as our Bird Safe Philly's monitoring efforts take off.

You Can Get Involved

Millions of birds die annually from window collisions. We need your help to make Philadelphia safer for birds, and that starts with learning more about where birds are colliding with windows in our area.The first step to fixing the problem is learning more about what kinds of birds fly into windows,
where they do it, and when they do it.

You can help us in this Community Monitoring effort by:

(1) looking for birds that have flown into windows around your neighborhood, workplace, and anywhere else you walk near buildings, and

(2) reporting information about those birds to Bird Safe Philly in our Bird Safe Philly iNaturalist Project.

Injured Black-throated BlueWarbler Sep 1

Injured Black-throated Blue Warbler. Photo: Stephen Maciejewski

Finding Injured or Stunned Birds

Most dazed birds found below buildings have suffered internal injuries from which they are unlikely to recover. Place your bird in a box with air holes and contact one of the area wildlife rehabilitation centers listed below. 
For more detailed guidance and to download this list of wildlife rehabilitation centers,
click here. Interested in volunteering to transport injured birds?  Learn more here.

Finding and Reporting Dead Birds

For more detailed guidance on what to do to report and potentially salvage dead birds for research at the Academy of Natural Sciences at Drexel University, click here.

Report a Collision

Contribute to our
iNaturalist Project

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