By: Carl Giometti

As we head towards the end of summer, temperatures start to fall, leaves turn bright colors, and billions of birds take to the sky to make their way south for the winter.  Human development in the United States has had a huge impact on bird migratory patterns; however, even in highly developed regions, hundreds of bird species can be found.  A single, small park in Chicago boasts over 340 species of birds spotted ranking it among the top parks for birds in the nation!! As architects and building owners, we can have a huge impact on the success of avian migration and make sure this crucial component of our ecosystem continues to thrive.

There are two principal issue when considering a building’s impact on birds: building materials and lighting.

Building Materials

Everyone loves big windows and walls of glass that wash interiors with daylight.  However, building glass provides significant difficulties for migrating birds; collisions with buildings account for an estimated 300 million to 1 billion bird deaths every year.  Clear glass is difficult for birds to perceive and they often fly into it, thinking there’s open space for them to occupy.  Alternatively, highly reflective glass often appears as another patch of sky that they can soar through.  Below are a list of architectural design “best practices” to minimize bird collisions:

  1. Don’t locate interior landscaping near glazing.  Planted atriums give a bird the impression that they can perch in that space.
  2. Avoid designs where you can see through a building.  Windows on opposite sides of the building look like a path a bird can fly to.
  3. Locate trees either immediately adjacent to glazing or at least 50 feet away.  If trees are up against a building, the bird is slowing, aiming for its perch rather than looking to fly through.
  4. Consider using fritted glass, sun shades, or other strategies to break-up large expanses of glass.  This is also a great opportunity to save energy and control harsh lighting levels inside.
  5. For existing buildings, schedule window washings to occur in early June to early August or late October to early March (i.e. outside the major migration period).  Dirt on windows allows some light to be refracted, allowing birds a better chance at seeing glass.


Migratory birds are amazing navigators.  For nighttime migrants, stars provide their map to guide them to their destination.  Light pollution interferes with a bird’s ability to recognize their location and successfully migrate.  Most municipalities set lighting level requirements at the property line but, also consider the light escaping upwards.  Avoid using building lighting that shines upward and use full cut-off fixtures.  LED lighting offers exciting opportunities to highlight building elements while limiting light lost to the sky.  Consider implementing measures recommended by Lights Out Chicago or the International Dark-Sky Association.  Light being thrown into the sky is energy and dollars wasted!

Migrating birds undergo an amazing journey.  For example, the Pectoral Sandpiper will leave the shores of Argentina in late April to fly 8,000 miles to its breeding grounds in northern Canada only to head back south a couple of months later.  Along the way, they’ll stop over on the Chicago lakefront, drainage ponds in the suburbs, and the wet prairies along the Illinois River.  By giving just a little attention to birds during building design, we can ensure they continue to do so for decades to come.



For more information, refer to the American Bird Conservancy’s “Bird-Friendly Building Design” guide as well as the website of Chicago Bird Collision Monitors.