Help Prevent Migratory Bird Collisions

By Stephen Living/DWR

On October 3, 2024, The Virginia Department of Wildlife Resources (DWR) received multiple reports of large groups of songbirds striking buildings overnight in the Shenandoah Valley. Bird collisions are an unfortunate common occurrence, especially during spring and fall migration.

In this case, localized foggy weather conditions combined with a large nighttime movement of migrating songbirds led to a widespread event with high bird mortality. DWR staff and partners collected dead birds from multiple locations. While weather was the suspected cause, DWR wanted to rule out any other reasons and sent a selection of birds to be evaluated by the Southern Wildlife Disease Study at the University of Georgia College of Veterinary Medicine. The results indicated that the birds were in excellent health and primed for their migration journey and had all suffered blunt force trauma consistent with a collision.

Biologists tackled the sad task of documenting the birds from the collision event. In all, 287 birds were collected from three sites. American redstarts, magnolia warblers, and Swainson’s thrush were just a few of the 23 different species identified. For some of the species, we counted more individuals than we had ever seen alive. It is likely that other locations in the area experienced collisions that went unreported, meaning the loss of birds was probably higher. This was one region over the course of a single night.

Why Does this Happen?

Many of North America’s songbirds migrate back and forth from breeding grounds in the north to more southerly wintering grounds, and most migrate at night. Migrating birds use a variety of methods to navigate: magnetic fields, stars, weather patterns, and topography. During a clear fall night you can hear the chips of songbirds passing overhead.

The developed landscape looks very different than the one these birds evolved migrating across. Building and bright lights confuse the migratory instincts of the birds and create hazards that they can crash into.

Fall migration begins in August and extends through November, but the peak migration activity in Virginia is from late September through early November. When winds from favorable weather provide a boost to birds flying south, hundreds of millions of birds may take the sky every night and navigate the challenging modern landscape. Recent studies have estimated that over 1 billion birds likely die from building collisions every year. With many of these species in steep decline, this is a huge conservation challenge.

What Can We Do?

Eliminating or reducing unnecessary lighting can significantly reduce bird collisions, while simultaneously reducing energy demands and costs to building owners. Reducing nighttime lighting is especially important during peak bird migration and periods of inclement weather.

There are a number of organizations promoting the reduction of artificial light during bird migration periods, including the U.S. Fish and Wildlife Service, Audubon, and Dark Sky International. In Virginia local groups like Bird Safe Hampton Roads are working to help address these challenges for migrating and resident birds.

Certainly, cities are a major source of light pollution, and individuals are limited in their ability to affect that, but Audubon’s Lights Out Network has information about how to communicate about the issue with local elected officials or building managers.

In addition, taking steps to ensure that birds can see and detect glass windows is another important step in reducing bird deaths. The American Bird Conservancy has great resources to help stop birds hitting glass

What Can Homeowners Do?

1. Turn off your interior and exterior building lights during peak migration seasons. (BirdCast is a good resource for this.)
2. If you can’t turn off all lights, consider turning off exterior lights—the flood lights that face up into the sky and rooftop lights that illuminate the surrounding landscape, or change your motion sensors to only be active when people are present.
3. Follow Dark Sky International’s Five Principles for Responsible Outdoor Lighting
4. Advocate for lights out in urban areas.
5. Treat windows that birds strike and those near bird feeders and other attractants.