Impact of Light and Glass on migratory birds

Building collisions, and particularly collisions with windows, are a major anthropogenic threat to birds, with rough estimates of between 100 million and 1 billion birds killed annually in the United States. The two major threats to birds are artificial light and glass. Most of the window-strike victims are migratory birds moving upwards in the spring to breed in the Arctic tundra or moving southward in autumn to winter in warmer areas, near the tropic or even South America.

In NYC, bird collisions are a significant issue. The city is home to over 8 million people, and is located along the Atlantic Flyway, a major migratory bird route. Over 450 species of migratory birds pass through NYC each year, making it one of the most important stopovers for migratory birds in the United States. However, the city’s tall, glass-covered buildings pose a serious threat to these birds. Glass buildings reflect and refract sunlight, making them invisible to the birds, causing them to collide with the windows. It is estimated that up to 230,000 birds per year die from collisions with buildings in NYC.

For the precious few who survive and are rescued, the Wild Bird Fund is their emergency room in Manhattan. Each year, the rehab team takes in about 1,200 window-strike victims, mostly migrating songbirds, such as warblers, vireos, and sparrows. After the recovery, patients are released back to nature.

Many of these strikes could be prevented by turning off the lights at night and using bird-friendly glass in buildings known to be hotspots for bird collisions. In order to promote the adoption of bird-friendly design both locally and as an industry standard, NYC Audubon supports bird-friendly policy and legislation through grassroots advocacy campaigns and outreach to stakeholders in the New York City government. December 2019 marked a major victory for NYC’s birds. The New York City Council passed Initiative 1482-2019, now Local Law 15, the most comprehensive bird-friendly building legislation in the U.S. This bill amends the New York City building code to require that new construction, and significantly altered buildings, use bird-friendly materials.

Text and photographs by Hector Cordero