Migratory birds like whooping cranes and tiny songbirds are making their seasonal flights over Texas to northern breeding grounds, with peak migration occurring from April 22 to May 12, according to Texas Parks and Wildlife. Nearly two billion birds of around 400 different species travel over the state each spring.
To help ensure their safe passage, the National Audubon Society is asking Texans to dim their lights as part of “Lights Out, Texas!”
The biannual campaign was launched as a statewide effort in 2020 by the Cornell Lab of Ornithology and BirdCast, a project that uses machine learning to help scientists predict how birds migrate based on weather patterns. That launch came a year after a study found Dallas to be the third most dangerous city in the United States for avian migration.
Dallas Mayor Eric Johnson’s office has partnered with the campaign and local businesses starting in 2020 to reduce light pollution during the fall and spring migration seasons. Downtown skyscrapers such as Whitacre Tower, one of AT&T’s corporate headquarters, and Reunion Tower have participated in the effort.
Nearly 80 percent of all North American birds migrate every spring and fall and around 70 percent of those birds are nocturnal travelers. The greatest obstacle during migration is light pollution, especially artificial light from urban areas, says Tania Homayoun, an ornithologist at Texas Parks and Wildlife. Scientists aren’t sure why that’s the case, but some research suggests that light pollution acts as an ecological trap, luring and throwing birds off course. Reflective glass on buildings like those in downtown Dallas and other city centers can further disorient a bird’s senses.
Birds don’t see glass as humans do, Homayoun says. “The cues that tell us that there is likely to be a window there or a glass door, birds don’t innately have those cues. … Sometimes they don’t see the glass or sometimes they see what they think is a reflection of trees and the sky that they can fly into.”
Some estimates suggest that anywhere from 388 million to 965 million birds die annually in the United States from building collisions. That comes out to about 12 to 30 deaths per second. As light pollution in North America grows by up to 10 percent annually, the number of fatalities could increase.
In 2017, Nashville and Blackburnian warblers were among the 20 species of migratory birds that died after colliding with a 32-story skyscraper in downtown Galveston. In 2023, nearly 1,000 migratory songbirds died after crashing into a mostly glass convention center in Chicago. Songbirds tend to fly at a lower altitude than other birds, Homayoun says, putting them at a greater risk of being drawn off course.
In downtown Dallas, the 37-story Whitacre Tower is dimming its exterior lights by 50 percent each night through May 12 from 6 to 11 p.m. during the peak of spring migration, AT&T spokesman Matthew Lawson said in an email. The building will completely turn off its exterior lights from 11 p.m. to 6 a.m. and then turn them back on at 50 percent brightness until sunrise.
Reunion Tower, the 50-story observation tower in downtown, is following a similar schedule, spokeswoman Jenna Guinn said in an email.
“Although our lights and light shows make us the icon of Dallas, we are more than happy to continue to participate in this [initiative] and help out our city in any way possible,” Guinn wrote.
“I’m sure every bit helps our feathered friends!”
It’s hard to gauge how dimming lights during migration season has helped birds in Texas because there’s not enough historical data to analyze, Homayoun says. But studies of efforts elsewhere have shown promising signs. A 2021 study published in the journal Proceedings of the National Academy of Sciences found that darkening windows of a large urban building in Chicago reduced bird collisions by 60 percent over a 20-year period. In Portland, Ore., the number of birds colliding into a governmental building dropped by 94 percent over a one-year period after the building’s glass windows were retrofitted with bird-safe film to reduce reflectivity.
On the iNaturalist app, volunteers can help monitor bird collisions and deaths by reporting their observations or taking photos, Homayoun says. And BirdCast’s live migration tracker allows users to follow the northward sojourn of migratory birds.
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