Wildlife advocates are urging residents across multiple regions to turn off nonessential exterior lights during the fall migration peak. Millions of birds traveling at night face severe risks of artificial light disorientation and deadly window collisions as they fly toward southern winter habitats.
As the autumn season gets underway, billions of birds embark on nocturnal journeys from northern breeding grounds to warmer climates in the south. Because roughly 80% of migratory birds travel under the cover of darkness, artificial illumination from cities and residential neighborhoods poses a severe ecological threat. Conservation groups and bird advocates are actively calling on the public to switch off outdoor lights during peak migration hours to keep the wildlife on course.
Regional Migrations and Urban Hazards in Milwaukee and Colorado
The movement spans major flyways, drawing public campaigns in states like Wisconsin and Colorado. In the Milwaukee area, advocates from Lights Out Wisconsin and the Southern Wisconsin Bird Alliance estimated that more than 24,000 birds would migrate through the immediate city while roughly 19 million traverse the broader state.
Similarly, wildlife experts along the Front Range of Colorado report massive nocturnal movements. Denver Audubon Communications Manager Dori Edwards noted the seasonal arrival of distinct species.
Edwards also pointed out that observers can spot yellow-rumped warblers, MacGillivray’s warblers, and numerous hummingbirds that remain unseen during the rest of the year. Radar data underscores the immense scale of these flights. Jacob Job, senior director of engagement and development at the Bird Conservancy of the Rockies, observed that the BirdCast project detected more than 5.5 million birds flying over Colorado on a single August night.
Why Artificial Lights Disrupt Ancestral Navigation
Migratory birds rely on ancient internal navigation systems that depend on natural environmental cues. Job explained the mechanics behind these nighttime journeys.
Despite these evolutionary adaptations, artificial lights pull birds off course. Job added simply, And, for some reason, birds are attracted to artificial lights produced by humans.
When bright urban illumination draws exhausted travelers into dense concrete environments, the danger multiplies.
Edwards explained that artificial lights lead birds directly into urban settings where they encounter domestic cats and reflective glass panels.
“It can lead them into cities where they’re more susceptible to other threats, so it’s not just the lights themselves, It’s that the birds can go towards the lights, and then they’re more susceptible to window collisions, which is a huge issue that we have in urban dense areas.”
Dori Edwards, Denver Audubon Communications Manager, via KUNC
Nationwide estimates emphasize the severity of the crisis. Adriaan Dokter, a research associate leading Cornell University’s BirdCast, told Ishani Desai that at least one billion birds die each year after crashing into skyscrapers and illuminated buildings. In New York City alone, more than 250,000 birds perish annually from window impacts, while rehabilitation centers like the Wild Bird Fund process hundreds of injured animals in early September alone.
Action Steps and Conservation Campaigns Through November
To mitigate these fatalities, conservation groups including the Audubon Society, Lights Out Colorado, and Lights Out Wisconsin are pushing for straightforward behavioral adjustments. Experts recommend turning off nonessential exterior lights from 11 p.m. to 6 a.m. throughout the migration window, which typically runs from early August through mid-November.
Brenna Marsicek of Lights Out Wisconsin emphasized the urgency of community participation in a public statement.
Property managers and homeowners can also install automatic motion sensors, shield outdoor fixtures to prevent upward light pollution, and close window blinds at night. Alongside these mitigation efforts, local organizations are conducting active research. In Colorado, Denver Audubon and the Bird Conservancy of the Rockies are partnering on bird banding sessions at the Denver Audubon Nature Center, allowing trained professionals to record data and track migratory populations as the seasonal transition continues.
