Bird Window Collisions: How Cities and Homes Can Protect Migrating Birds

Urban glass and artificial night lighting create deadly traps for migrating birds. This episode follows citizen-scientist volunteers who document window-strike victims and explains why collisions spike during migration. It highlights how reflective and transparent glass misleads birds, the data behind bird-death estimates, and how targeted design changes can cut fatalities. Lessons from Chicago's McCormick Place and the Lights Out DC initiative show how simple window treatments can have large effects, while local building codes begin to standardize bird-friendly design. Listeners are given actionable steps for homes and businesses to reduce bird deaths and support urban conservation.

Introduction and the collision problem

Night migration turns cities into corridors where hundreds of millions of birds fly unseen above us, and glass becomes a fatal trap when they rest or search for roosts in the early morning. The episode explains that birds navigate using the moon and stars, but artificial lights and reflective or transparent windows disrupt that navigation and lead to collisions. Volunteers across the United States, including Washington DC, professional researchers, and conservation groups, collect data on window-strike victims to quantify the scope of the problem and identify hotspots where deaths concentrate.

"Birds navigate by the moon and stars, but glass is a deadly trap." - Nell Greenfieldboyce, NPR

Mechanisms and urban patterns

The report emphasizes that most collisions occur low to the ground, not just on skyscrapers, with 1-3 story buildings accounting for many fatalities due to sheer prevalence. In urban canyons, certain buildings create travel routes that funnel birds toward fatal glass surfaces, a phenomenon described as the walkway of death. The data from groups like Lights Out DC feeds into larger scientific estimates and informs outreach to property managers and city planners.

"Most collisions are happening down low, like below the tree line, not just skyscrapers." - Brian Lenz, American Bird Conservancy

Solutions, pilots, and policy shift

The piece documents proven interventions, including patterns of dots or lines on glass that deter birds from attempting to fly through—patterns shown to dramatically reduce collisions when applied to large window surfaces. A watershed moment occurred after a mass collision at McCormick Place in Chicago, which spurred a city-wide decal solution and helped launch the Bird Collision Prevention Alliance, a coalition of organizations focused on science-based, non-political approaches to bird safety. The alliance produces practical toolkits for diverse scenarios, from cruise ships to office campuses, and promotes local building-code changes rather than broad federal policy debates.

"Covering full windows with a pattern of dots reduced bird collisions at McCormick Place by 95 percent." - Tina Phillips, Cornell Lab of Ornithology

What homeowners and cities can do now

Beyond large-scale interventions, the episode offers concrete steps for individuals: identify windows that have caused thunking impacts, apply bird-friendly treatments to vulnerable panes, and consider proximity to feeders, fruit trees, or baths that attract birds to reflective surfaces. Cities like DC and New York are adopting local policies to require bird-friendly construction at the bottom 100 feet of new buildings, while renovations in Dallas and San Francisco demonstrate how public pressure and data can drive change even in existing structures. The program closes on a hopeful note: with data, collaboration, and local action, avoidable bird deaths can be substantially reduced.

"Turn off nighttime lights and apply bird-friendly window treatments to homes and offices." - Brian Lenz, American Bird Conservancy