Birds migrating at night are attracted to artificial sources of light, particularly during periods of inclement weather. As birds approach the lights of tall buildings, communications towers, lighthouses, floodlit obstacles, and other lit structures, they become vulnerable to collisions with the structures themselves.
Once inside a beam of light, birds are reluctant to fly out of the lighted area into the dark, and often continue to flap around in the beam of light until they drop to the ground with exhaustion. A secondary threat resulting from their aggregation at lighted structures is their increased vulnerability to predation.
Reducing building lighting during migration seasons can drastically reduce the hazard of building collisions. In 2006, the Detroit Audubon Society initiated Safe Passage Great Lakes. In partnership with Michigan Audubon, this program encourages building owners and occupants to turn off lights above the fifth floor, and take other simple steps during the peak migration seasons of mid-March through May and mid-August through October to reduce the danger as migrants pass through. Major cities in our region including Chicago and Toronto, as well as New York City, Washington D.C., Portland, Oregon, and many others, have started similar programs with demonstrated records of success.