why do birds hit buildings?

Birds hit buildings for any of these three reasons:

  • reflections
  • false fly-throughs
  • artificial lights


bird collision reflection hazard tree animalia project
Is this tree real or a reflection? You probably guessed it’s a reflection, because you recognized the window frames. Birds often confuse this reflection for a real tree, then strike the window when they fly toward the ‘tree’. (photo by susan ask)

During the day, birds can fly head-on into windows, confused by the reflection of trees, clouds, buildings, or skyline in building facades.

We can be confused by reflections too, but we read other cues, such as window frames, to help us distinguish reflection from reality.





false fly-throughs

bird collision hazard: trees seen through windows. animalia project.
These trees, planted inside a building, pose a hazard to birds. When birds fly towards the trees, they can collide with the windows, because they don’t see the glass in front of the trees.  (photo by susan ask)

Birds also collide with glass when they attempt to fly towards something, like the tree in the lobby pictured below, that is visible– but inaccessible– because of a glass barrier.

It’s become popular to plant trees in large glass atria.  But these lobbies are a real hazard to migrating birds searching for food and shelter when they stopover in cities.




artificial lights

bird collision hazard lights animalia project susan ask
Artificial lights can confuse migrating birds. (photo by susan ask)

At night, artificial lighting can confuse migrating birds, causing them to fly until they are exhausted.





Learn more about solutions to bird collisions here.