May 2002

From Field Museum

Turning off building lights reduces bird window-kill by 83%

Field Museum scientists release data from two-year study

CHICAGO--New data never before published reveals that turning off building lights in a major city could save thousands of migratory birds a day. "For the first time, we now have numbers to back up scientists' claims that turning off building lights during migration season is an effective way to reduce the number of birds who kill themselves by flying into buildings," says Doug Stotz, PhD, a conservation ecologist at The Field Museum.

During 2000 and 2001, Stotz and his colleagues counted dead birds around McCormick Place every day during the migration seasons--from 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%. "That's 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 Interior's 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.

The Chicago Ornithological Society estimates that 100 million to 1 billion birds die annually by colliding with buildings in the U.S. alone. Canada is ahead of the U.S. in studying and preventing bird-building collisions. Michael Mesure, executive director of the Fatal Light Awareness Program in Toronto, will speak at The Field Museum on the causes and solutions to this problem on May 20. The 7 p.m. lecture is part of COS' monthly meeting. Mesure will outline his experiences working with building managers, architects, window manufacturers and public officials to reduce night lighting problems and window kill.

Day Light conditions Dead Birds Reduction per window night

All Windows Same, Either Dark or Light:

Lit windows 613 Dark windows 46 88% Windows Mixed, Either Dark or Light:

Lit windows 684 Dark windows 146 83%

Total: Lit windows 1297 Dark windows 192 83%

Most common window casualties at McCormick Place 1978-2001

Song Sparrow 3968 Dark-eyed Junco 3393 Swamp Sparrow 2987 White-throated Sparrow 2257 Hermit Thrush 1322 Fox Sparrow 1165 Ovenbird 1154 American Tree Sparrow 986 Lincoln's Sparrow 915 Tennessee Warbler 871

Day

Light conditions

Dead Birds

Reduction
per window night

All Windows Same, Either Dark or Light:

Lit windows

613

Dark windows

46

88%

Windows Mixed, Either Dark or Light:

Lit windows

684

Dark windows

146

83%

Total:

Lit windows

1297

Dark windows

192

83%











This article comes from Science Blog. Copyright 2004
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