Flying Dark

Turning out lights at night is for the birds.

by Melissa Gaskill

One spring night in 2017, about 400 migrating birds crashed into Galveston’s One Moody Plaza, home to American National Insurance. Twenty large lights, which illuminate the building, likely disoriented the fliers, luring them to their deaths.

The company immediately turned the lights off, says Kathy Sweezey, bird-friendly communities program manager for Houston Audubon, and has continued to do so during peak migrations ever since. Buildings in Houston and Dallas are joining in as part of a campaign called Lights Out.

This nationwide initiative, sponsored by BirdCast, a consortium of ornithology researchers, aims to protect migrating birds from collisions with buildings. North America lost 3 billion birds in the past half-century, says Cornell University scientist Benjamin Van Doren, and building collisions are a significant factor in that remarkable loss, killing millions of birds each year. 

Research shows that simply turning off a building’s lights can drastically reduce the carnage.

For decades, scientists from Chicago’s Field Museum collected dead birds around the city’s convention center, McCormick Place. Van Doren and his colleagues used the data to show that darkening half the windows produced 11 times fewer bird collisions during spring migration and six times fewer collisions during fall migration.

Lights both attract and disorient birds, which then run into glass on lighted buildings, says Doug Stotz, senior conservation ecologist at the museum.

“Many birds migrate at night, using the stars and moon to orient, and lighted buildings seem to confuse them,” Stotz says, adding that Chicago is the country’s deadliest city for migrating birds, with Houston right behind. “It’s a big city with lots of lights and tall buildings along probably the densest flyway of migrating birds.”

In fact, roughly one of every three birds migrating through the U.S. in spring and one of every four in fall — nearly 2 billion total — pass through Texas. After Chicago and Houston, Dallas is ranked the third deadliest city for migrating birds.

Houston's buildings, above, are deadly to birds; turning off lights can help birds have a successful migration.

Migration is the deadliest time of life for birds. The Lights Out campaign focuses on peak migration periods, as forecast by BirdCast, using the U.S. Weather Service’s network of radar stations.

“In addition to quantifying water, snow and hail in the atmosphere, the radar also picks up living things such as migrating birds,” Van Doren says.

Researchers combined more than two decades of migration tracking data from the radar network with concurrent weather conditions, then used machine learning (a kind of artificial intelligence) to determine relationships between migration and weather. Using those results, it’s possible to forecast migrations three days before they happen.

“When we know that lots of birds are likely to be migrating through part of Texas two days from now, we issue a lights-out alert for that particular location,” Van Doren explains.

Targeting peak periods is important, says Julia Wang, BirdCast Lights Out coordinator, because bird migrations span large periods of time.

“It can be a hard sell to ask people to turn out lights all the time, so we look for the most effective time to do so,” she says. “Peak migration is when about 50 percent of migrants in that season are moving, about three weeks in spring and a month-and-a-half in fall. The majority of collisions happen on nights when higher numbers of birds are migrating, so we prioritize those nights.”

Peak migration this spring is expected from April 22 to May 12; fall’s is predicted to be Sept. 6 to Oct. 11. Houston Audubon has been reaching out to ask building owners to go dark during that time.

As additional motivation, turning off lights can also save money; according to the EPA, energy is the largest operating expense for commercial buildings.

“I love to show that turning off lights not only protects birds, but helps businesses and people as well,” Sweezey says. “You can save a lot of money by turning off lights at night, especially lights that aren’t being used. And it supports other environmental causes such as reducing emissions.”

Volunteers inventory dead birds collected as part of the Lights Out Texas campaign in Dallas.

When hundreds of birds die in a single night, skyscrapers are the obvious culprits, but nearly half of window strikes likely happen at home windows.

“We may not know specifically how much the average house is affecting the average nocturnal migrating bird,” says Van Doren, noting the size differences between apartments and homes. “We know that lights affect birds and it does make a difference if you turn off your home lights. A win-win situation, saving birds, energy and money.”

Every dimmed light matters.

“Bigger buildings with brighter lights tend to be the main cause for concern, but any little bit helps,” Sweezey says. “It’s not just about the birds — all kinds of animals get distracted by lights.”

Night lighting has even been shown to have negative effects on humans, disrupting our circadian (or daily) rhythm and contributing to the development of certain diseases.

An important element of the Lights Out campaign has been education.

“Some reasons why people do not participate are simple lack of understanding or awareness of the issue, even about the fact that a lot of birds migrate at night,” Wang says. “Competing desires can be an issue with companies. They may have concerns about loss of business, worrying that if lights are out downtown, it looks closed. But once we get one or two buildings to do it in a major city, it is easier to get others on board.”

Experts stress that the idea is turning off nonessential lights, such as those in unused offices at night or decorative lights on trees, while maintaining safety.

Turning lights out is not just a building manager’s decision.

“At American National, it was employees who were concerned and took the initiative to speak up,” Sweezey says. “Anyone at any level, no matter their position, can speak up if they want their building to turn out the lights. Birding is a big part of the economy in the Houston area, and all of Texas.”

Houston Audubon began monitoring the effects of Lights Out efforts in 2021 (after a pandemic-related delay). During spring and fall migration, monitors walk around downtown Houston early in the mornings, counting dead birds and recording data such as species and location. This helps identify trends, including whether some types of birds are more susceptible to flying into buildings, and whether the effort is making a difference.

Brightly lit buildings are only one of many hazards migrating birds face; others include loss of stopover habitat and food sources, obstructions such as cellphone towers and turbines, predation (domestic cats) and reflective glass glare in sunlight.

Yet night lights remain one of the most significant causes of death, and fortunately, one of the easiest to fix. Just ask the folks at One Moody Plaza.

Melissa Gaskill is an Austin freelance writer