Bird-Window Collisions: Community Data, City Codes, and Home Solutions to Protect Migratory Birds

Migratory birds collide with glass as they navigate urban spaces at night, a problem that spikes during migration season. The episode follows volunteers who count window-strike victims across cities, highlights a landmark Chicago mass-death event at McCormick Place, and explains how data led to practical solutions like dot patterns on windows and bird-friendly building codes in cities such as DC, New York, and San Francisco. It also outlines steps homeowners can take to reduce collisions, from turning off lights to applying exterior window treatments. The episode emphasizes data-driven advocacy and collaboration among researchers, conservation groups, and city planners to save birds at scale.

Overview: The Window Collision Challenge for Migratory Birds

The NPR Shortwave episode centers on a problem that often goes unnoticed: glass windows injure or kill migratory birds as they route across urban landscapes. At night, birds navigate by the moon and stars, but artificial lights and reflective or transparent glass create deadly traps. The host, Emily Kwong, and NPR science correspondent Nell Greenfieldboyce explain that billions of birds are affected each year, with collision death spikes during migration season. The discussion sets the stage for a data-driven approach to understanding and mitigating this issue, moving from abstract concern to concrete actions in cities and homes.

One striking point is the sheer scale: researchers estimate at least a billion US birds are killed by window collisions annually. This stark figure helps justify the need for coordinated efforts that combine citizen science, architectural redesign, and policy changes. The episode also introduces volunteers who wake up early to document injured or dead birds along sidewalks, creating a valuable database that informs researchers and city officials about where and why collisions occur.

"Researchers estimate that every year in the US, collisions with windows take out at least a billion birds." - Nell Greenfieldboyce, NPR science correspondent

From Data to Action: How Volunteers, Researchers, and Cities Respond

The program spotlights Lights Out DC, a volunteer network that records window-strike victims and compiles long-running data. This data feeds broader research and helps make the case for prevention measures. The conversation highlights how a small number of buildings account for a large share of bird deaths, especially those with complex glass layouts that act as death traps. A vivid example is the McCormick Place convention center in Chicago, where a mass collision in which thousands of birds died over a short period prompted a systemic response. Following that event, officials and researchers collaborated to test and implement bird-friendly window patterns that significantly reduce collisions.

"11,000 birds died in one night crashing into one building." - Tina Phillips, Cornell Lab of Ornithology

Proven Solutions: Patterns, Policies, and Partnerships

The episode details effective mitigation strategies, including window decals or patterns that create a discernible barrier for birds. Chicago’s convention center adopted a dot pattern across its glass, resulting in a dramatic 95% drop in collisions. This success catalyzed the formation of the Bird Collision Prevention Alliance, a coalition spanning federal agencies, universities, architecture firms, and conservation groups that develops practical toolkits for different environments, from cruise ships to office campuses. The alliance emphasizes non-partisan, science-driven work focused on scalable solutions rather than broad political fights.

"data taken before and after shows that this actually reduced bird collisions there by 95%." - Tina Phillips, Cornell Lab of Ornithology

Household Steps: Small Changes that Add Up

The program concludes with guidance on what homeowners can do to protect birds at home. Treating windows near feeders, fruit trees, or other attractants with exterior patterns helps prevent strikes. The episode also reinforces the simple but powerful idea that turning off nighttime lights during migration can reduce disorienting attractants for birds and minimize hazards near urban glass went the birds are most vulnerable. By combining home measures with city-level building codes and ongoing data collection, communities can reduce bird deaths at scale while preserving urban life for people and wildlife alike.

"If you take those windows and put a bird-friendly solution on the outside, you probably will never hear another collision at your house again." - Brian Lenz, American Bird Conservancy