Turning Off Your Lights Could Save Millions of Birds Each Year from Deadly Building Collisions

Artificial lights wash out the stars that guide bird migrations, luring them into a maze of treacherous obstacles and highlighting the need to preserve the dark night sky

Ovenbirds (Seiurus aurocapillus) are commonly found on city streets after an evening migration, and saving specimens in the museum’s ornithology collection allows researchers to monitor the species’ population decline. Emma Saaty, NMNH

City buildings are filled with the sounds of shuffling papers, ringing phones and the dull buzz of artificial lights that illuminate the structures deep into the night.  Occasionally an unexpected “Thud” pierces through the ambient noise and shudders the glass windows: migratory birds brought to a sudden stop on their long journeys, never to reach their final destinations.

Since the dawn of biological history, organisms on Earth have evolved under the consistent cycle of light and dark.  This pattern acts as a cue, telling different species when to eat, sleep, mate and migrate.  But the signal is becoming increasingly dim as artificial lights blur the line between day and night.  This International Dark Sky Week, learn why we need the dark, and discover how the Smithsonian National Museum of Natural History’s newest exhibition “Lights Out: Recovering Our Night Sky,” utilizes the museum’s extensive collections to illustrate the ecological implications of light pollution.

Over 33% of the world’s population cannot see the Milky Way galaxy due to light pollution, and for birds that navigate using the stars, this hazy sky is causing deadly results. Todd Carlson

The vast majority of artificial light is not needed by humans, and every extra streetlight or perpetually lit office building contributes to light pollution.  Now, more than 80% of people live under light-polluted skies, and that number continues to rise.  “The night sky has been there for all living creatures since day one, and I don't think we yet realize what is lost when we cut off that connection to something beyond us” says Kimberly Arcand, the co-curator of the museum’s new exhibition and a visualization scientist at the Center for Astrophysics | Harvard & Smithsonian.

A striking example of this loss can be found in the labyrinth of metallic cabinets that comprise the Smithsonian’s Division of Birds, scientific collection.  Each year an estimated 300 million to 1 billion birds are killed due to collisions with artificially lit buildings. Many of the most impacted species are collected and kept as specimens in the museum so that researchers can monitor the issue as it escalates.

Billions of birds migrate north and south through the Americas, and every year millions are killed as they face obstacles such as exhaustion, predation and building collisions due to vast landscapes of artificial lighting. Smithsonian Institution

“We have just under 600,000 bird specimens in our collections,” says Brian Schmidt, a museum specialist in the NMNH Division of Birds and a key contributor to the new “Lights Out” exhibition.  “During the migration season birds are hitting city buildings every single morning, and we have taken as many as we can into our collection.”  Clear nights are best for bird migrations as there are few predators, cooler temperatures that prevent exhaustion and the moon and stars act as guideposts for the birds to follow as they travel north or south.

As the birds begin to tire in the early hours of the morning, they are drawn towards huge expanses of twinkling city lights that obscure their celestial directions in the skies above.  Just as humans in densely populated cities have trouble making out the big dipper and the milky way, birds that fly over these same cities become disoriented and confused by the sudden artificial glow.

“The night sky has been there for all living creatures since day one, and I don't think we yet realize what is lost when we cut off that connection to something beyond us.” — Kimberly Arcand, visualization scientist at the Center for Astrophysics | Harvard & Smithsonian

For reasons that remain enigmatic, birds are drawn to these urban illuminations. As their weary wings bring them down to rest, they run right into the colossal city buildings below.  “Imagine you are on a road, and headlights shine in your eyes making you miss your turn,” says Christina Gebhard, a museum specialist in the NMNH Division of Birds.  “The next thing you know you are 30 miles down the wrong road and you’ve run out of gas.”

Both Schmidt and Gebhard believe that artificial lights and building collisions have added to the noticeable decline in bird populations that has been documented in recent years.  When the museum’s exhibition team asked the researchers to contribute to “Lights Out,” they quickly agreed. They hoped to open the visitors’ eyes to how leaving their lights on at night could spark a major ecological impact.

The pair put together a hauntingly beautiful display showcasing 20 species of birds that routinely hit windows and buildings in the Washington D.C. area.  Most of these birds were collected by volunteers with Lights Out DC, a program run by the nonprofit organization City Wildlife.

Brian Schmidt, a museum specialist in the NMNH Division of Birds, holds open a drawer of Gray Catbirds (Dumetella carolinensis) that were featured in the museum’s newest exhibition, “Lights Out: Recovering Our Night Sky.” Emma Saaty, NMNH

At 5:30 in the morning, before the sun peeks out over the marble monuments, a small group of volunteers sets out and scours local sidewalks for any signs of avian life that have hit D.C. buildings overnight. They aim to rescue birds who survived their collisions and donate dead specimens to various museums across the country.

“Every day we hope not to find any birds that have been injured or killed, but they are always around,” says Lisbeth Fuisz, coordinator and longtime volunteer of Lights Out DC.  “These are populations that are already being stressed by lots of other problems such as habitat loss, cat predation and getting hit by cars, and this magnitude of loss is not sustainable in the long run.”

However, Fuisz stresses that this is a fixable problem, and that everyone can make changes that will help save these birds.
Volunteers with Lights Out DC walk the streets in the early morning, finding dozens of dead birds each day such as this American Woodcock (Left) and Song Sparrow (Right) that where both found in the last month. Barbara Lautenbach and Ananke Krishnan, Lights Out DC

The first and simplest solution is dimming and turning off unnecessary lights at night, an adjustment that has been shown to drastically decrease migratory bird collisions. “Lights Out” campaigns have already been successfully introduced in cities around the world and can be implemented at every level from family homes to large office buildings.  Migration forecast maps allow citizens to keep track of the bird migrations in their area, and the International Dark Sky Association has highlighted five principles for responsible outdoor lighting.

Other key steps include getting involved with local policy and supporting birding groups that are working to make changes on a larger scale.  Last year, City Wildlife and a coalition of local environmental groups helped get the Migratory Local Wildlife Protection Act passed, which legally requires new buildings and remodels in Washington to use patterned, bird friendly glass.  Bird advocates and researchers alike stress that because light pollution is caused by humans, every individual can be part of the solution.

“Before I began working with Lights Out DC, I don't think I realized the extent of the problem that glass and light pollution posed to birds,” Fuisz says.  “Once your eyes are opened to what is going on with these birds, it can be deeply upsetting, but it also goes straight to your heart and becomes your mission.”

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