During 2000 and 2001, Stotz and his colleagues counted dead birds around McCormick Place every day during the migration seasonsfrom late March to the end of May and from mid-August to Thanksgiving. Half of the vertical surface of the huge, lakefront building is glass, and lights in the building seem to disorient migrating birds, which typically navigate by the stars.
Turning lights off at McCormick Place reduced the number of dead birds by up to 88%, depending on lighting conditions and window location. For all the days counted, 1, 297 birds died from hitting lit windows while only 192 birds died from hitting dark windows (either because the lights were out or heavy drapes were drawn). After adjusting for the variance in lit versus dark windows, the overall reduction was 83%. Thats an incredible savings from just one building, Stotz says. Imagine what we could accomplish if the drive to turn off lights during migration season spread to include most downtown buildings.
The City of Chicago is working toward that very goal. In 2000, Chicago and the U.S. Department of Interiors Fish and Wildlife Service signed the Urban Conservation Treaty for Migratory Birds. Ever since, the city has been asking downtown buildings to dim or shut off their lights in the spring and fall.
Field Museum scientists have been checking for dead birds at the base of McCormick Place since 1978. Over the years, they have collected 29,842 birds of 140 species. The most common window casualty was the song sparrow, Metospiza melodia.