Lights Out Denver

Lights Out Denver (LOD) is an initiative of Denver Parks and Recreation. Part of Denver’s commitment as an Urban Bird Treaty City, the program aims to increase awareness of migratory bird collisions with buildings in the City and County of Denver, and to promote practices that can help prevent these needless deaths. This program collects data on bird strikes in downtown Denver during spring and fall migration to identify threats to migratory birds and to demonstrate the necessity of bird-friendly building regulations. LOD also provides information on how individuals, businesses, property owners and managers can help reduce migratory bird deaths. Our goal is to help local businesses save energy, money, and migratory birds by promoting bird-safe building designs and reducing nighttime lighting! 

Learn more about threats to birds, including collisions with buildings and glass.

Bird migration in Denver

Denver is along a principal route of the Central Flyway, which birds use to make their yearly journeys from their breeding grounds in the north to their wintering grounds in the south. Denver provides a wide range of habitat for more than 300 bird species that migrate through or nest in the city. While exact timing varies year to year, spring migration generally occurs from mid-March to the beginning of June and fall migration occurs from mid-August to the beginning of November.


How are buildings a threat?

Building collisions are a leading cause of bird fatality during migration in North America, with the American Bird Conservancy estimating that up to one billion birds die each year in the United States from building collisions.

Why do window strikes happen?

  • Birds cannot see glass, they can only see what the glass reflects.
  • Glass often reflects open sky, trees, and other vegetation that is desirable to the birds. Collisions occur when birds attempt to access this reflected habitat and fly into the glass.

Why is nighttime lighting a problem?

  • Birds are attracted to artificial lights at night, drawing them into light-polluted city centers and increasing their chances of striking a building
  • This problem is amplified during spring and fall migration, as most of our native birds migrate at night
  • Nocturnal migrators use the moon and stars to aid in navigation and become disoriented by artificial lights at night; birds may confuse building lights for stars and fly in circles around the buildings and die of exhaustion or collide with the windows

What factors make buildings unsafe for birds?

  • Windows: More glass leads to more strikes. As the percentage of window surface on a building increases, so does the risk of avian mortality
  • Height: Buildings do not have to be tall to be a threat to birds; most collisions occur in the first 3 floors of a building. While tall buildings kill more birds per building, individual residences kill more birds cumulatively
  • Vegetation: Landscaping near building windows attracts birds
  • Trees reflected in windows and potted plants inside windows confuse birds and increase the chance of a collision


How can we reduce building collisions?

  • Turn off lights at night
  • Move vegetation away from windows
  • Install bird-friendly decals on windows to help birds perceive glass as a barrier
  • Create legislation and city ordinances that address bird-friendly building designs


Benefits of reducing nighttime lighting

Turning out lights yields many rewards:

  • Energy and cost savings
  • Reduced light pollution
  • Decrease in CO2 emissions
  • A safer environment for birds
  • A healthier environment for us all


How you can help

Lights Out Denver needs your help collecting data on bird collisions in downtown Denver. Join our team of citizen scientists and patrol routes, collect data, and help transport injured birds to wildlife rehabilitation centers. Your efforts are vital for this program to succeed! By monitoring for bird collisions, you can help gather the data we need to convince building owners and legislators that Denver needs to step up, and turn lights off, to protect birds.

For more information about volunteering, contact



Lights Out Denver Partners

The Lights Out Denver program could not succeed without the support of our partners. Learn more about these organizations below: