Each year, an estimated 365 million to 1 billion birds die by smacking into reflective or transparent windows in deadly cases of mistaken identity, believing the glass to be unimpeded sky. “These birds are dying right in front of their eyes,” said Connie Sanchez, the bird-friendly buildings programme manager for the National Audubon Society, which for two decades has asked cities to dim their lights from about mid-March through May and again in the fall, under its Lights Out initiative. Since late last year, at least six cities have joined forces with the 35 other places where the society, local organisations, ornithology experts and some of the nation’s largest companies have been helping birds navigate in urban centres. The efforts are gaining ground in cities including Chicago, Houston and New York City, which are among the top 10 in the United States for light pollution. Cities from Dallas to Philadelphia take part. The timing of the lights-out campaign varies based on location. In Texas, whose coastal lands are the first that birds encounter after they cross the Gulf of Mexico, buildings will go dark in Dallas from mid-March through May. In Fort Worth, at least 11 of the city’s most prominent buildings will dim their lights from midnight to 6 am through May 31. In Jacksonville, Florida, where migration started in mid-March, building owners and managers are examining data from volunteers who walk the city, collecting carcasses and documenting where birds have fallen. Buildings in Philadelphia have also joined the nationwide effort, a step that experts hope will help to avoid a repeat of the deaths of more than 1,000 birds last October, an event reported by The Philadelphia Inquirer as one of the largest such avian fatalities in decades. Finding dead birds, and what killed them. Bird populations are already imperilled by climate change, habitat loss and cats. Turning lights out at night can mitigate one more risk to their lives, experts say. But before a city knows if a lights-out campaign will work, it first has to know how many birds it might help. The Cornell Lab of Ornithology has used radar data to identify abnormal bird densities. In some cities, the approach is old-fashioned shoe leather. Three days a week, at about 7 am, volunteers hit the streets of Jacksonville, peering into shrubs or searching the bases of the city’s tallest buildings. In the week of March 14, they found two warblers and a dove. The tiny bodies were put into bags and handed over to the zoo for analysis. Then the business of forensics begins. As in any cause of death investigation, clues must be extracted from their surroundings. In the case of birds, the only certainties are flight, gravity and thin air. Moments after a fatal impact, birds plummet to sidewalks, drop onto high-rise ledges inaccessible to the public or sink into bushes on private land until discovered there inexplicably dead, throwing the possible answers to the who, what, when and where of their deaths into disarray. Sometimes, stunned by the impact, they keep flying before they fall, making the place of their original blow difficult to trace. Often, cleaning crews sweep up carcasses before the volunteers can document them. Mike Walker, a curator at the Jacksonville Zoo and Gardens, who works with the volunteers, said cats will also get to the birds. “We don’t know if they caught the bird or just took advantage of this free meal that fell to the ground in front of them,” he said. Last October in Philadelphia, an estimated 1,000 to 1,500 birds in one night flew into buildings in a radius of just over three blocks of Centre City, possibly because of a low ceiling of bad weather that interfered with migrating birds from Canada, Maine, New York and elsewhere toward Central and South America, The Inquirer reported. After the event, Audubon Mid-Atlantic, the Academy of Natural Sciences of Drexel University, the Delaware Valley Ornithological Club and two other local Audubon chapters formed a coalition to tackle the problem. The response has been “extremely robust” among the city’s iconic properties, said Kristine A Kiphorn, executive director of the Building Owners and Managers Association in Philadelphia. Comcast, One and Two Liberty Place and the Wells Fargo Centre are among the 30 buildings that have so far signed up to go dark this spring. “We feel it makes ethical, ecological and economic sense,” she said. FLIP A SWITCH, SAVE A LIFE Bird strikes against buildings have been recorded for decades in Philadelphia. The first recorded window kills date back to the 1890s, when City Hall was lit up, said Nate Rice, the ornithology collection manager at Drexel’s Academy of Natural Sciences. Rice said the academy’s database now has 823 specimens that have been identified as window strikes in Philadelphia. 
 
 A handout photo shows birds that died after flying into buildings in Philadelphia in October, 2020. Buildings, landmarks and monuments are turning off lights to prevent fatal impacts as birds set off on spring migration. The New York Times 

“If we can generalise, say, ‘Let’s keep lights out or at a minimum during peak migration time,’ this can have an impact on wild bird populations,” he said.  A handout photo shows birds that died after flying into buildings in Philadelphia in October, 2020. Buildings, landmarks and monuments are turning off lights to prevent fatal impacts as birds set off on spring migration. The New York Times  Modern architecture has accelerated the problem as sky-piercing, reflective structures are illuminated at night. Birds use stellar navigation, and twinkling lights — especially on overcast nights — can confuse them, leading them to fly in circles instead of proceeding along their route. Others drop exhausted to the ground, at risk of predators, cars or smacking into glass when they take wing again. Some crash into buildings if they see a plant in the window or a tree reflected in the glass. Many buildings do more than flip a switch. Some use glass with patterns to help birds differentiate between open sky and a deadly, transparent wall. In Chicago, architects have angled exteriors. In Galveston, Texas, a pulse was added to safety bulbs on tall buildings. Fort Worth’s Frost Tower turns off its light and asks tenants to do so as well, using slides in the lobby to explain why. Every year in New York City, the twin beams of light in the tribute to 9/11 victims are turned off at peak times to help free birds that have been drawn to the lights. The Cornell Lab of Ornithology estimated that the memorial’s lights altered the migratory behaviour of more than 1.1 million birds over seven nights in September. And in St Louis, exterior lights at the Gateway Arch landmark are turned off at night to avoid disorienting birds during migration in the first two weeks of May, when warblers and other birds fly from Canada to Central and South America. With the help of volunteers who are canvassing for bird bodies, the local Audubon chapter is preparing to introduce a formal Lights Out programme for the city. “We wanted to see what areas of downtown are causing problems to birds,” said Jean Favara, vice president of conservation at the St. Louis Audubon Society. “I hope by 2024, we will have 30 to 34 buildings enrolled, and we can go from there.” ©2021 The New York Times Company