Dark Nights, Safe Flights: How Turning Off Lights Helps Migrating Birds

Each year, migratory birds cross vast distances and many travel at night, when artificial lighting can alter their routes and behavior. Scientists have estimated that collisions with buildings kill between 365 million and 988 million birds annually in the United States, and conservation groups often use a rounded figure nearing one billion to communicate the scale of the problem. Light pollution can both attract birds toward lit areas and disorient individuals once they arrive, increasing the risk of fatal window strikes.

In one striking episode in Chicago, nearly 1,000 migrating songbirds were found dead after a single night when birds were drawn into bright lights and then collided with glass and structures. Events like that have strengthened calls for temporary darkening of skylines during peak migration, while monitoring projects have documented the effects of such actions.

Practical responses have been developed at multiple scales: forecasting tools such as BirdCast are used to predict heavy migration nights, Lights Out programs ask building managers and residents to dim or extinguish non-essential lighting from about 11 p.m. to 6 a.m., and some cities now require bird-safe design elements or offer guidance for retrofits. Architects and engineers are increasingly specifying patterned glass and other deterrents so that collisions will be reduced over time.

Individuals can contribute immediately by dimming indoor lights, shielding outdoor fixtures, closing curtains, and reporting collision victims to monitoring platforms. Consequently, while structural solutions are being adopted gradually, the simple act of reducing light on key nights has been shown by monitoring and field work to lower the number of collisions.