‘No one wants a building that kills birds': why cities are turning off the lights

The Guardian

15-05-2025

The wren's legs were tucked delicately underneath its diminutive body, slumped on its side as if asleep. If it wasn't lying on the bare concrete of a Texas street, there would be few clues that it had endured a crunching, violent death.
The bird had flown head first into the Bank of America building, a 72-storey modernist skyscraper in the heart of Dallas. Its corpse was catalogued by volunteers who seek to document the toll of birds that strike the glass, metal and concrete structures festooned with bewildering lights that form the skylines of our cities.
It's estimated that around a billion birds die across the US each year in this way, one of the leading drivers of an alarming slump in numbers. For the dozen volunteers gathered before dawn to scour downtown for newly dead birds on a balmy May morning, each of these losses is a solemn one.
'If you let it sink in too much about what you're doing every morning, it wears you out, it can be pretty bleak,' says Tim Brys, a community engagement manager at the Perot Museum of Nature and Science and regular bird surveyor for the Lights Out, Texas! campaign. 'It's horrible to think these birds have flown all the way across the Gulf of Mexico only to fly into the first glass building.'
The buildings of Dallas, along with those of other Texan cities, are particularly lethal obstacles because they sit on the central flyway, a major migratory route taken by birds as they traverse North and South America. It's thought as many as one in three birds migrating through the US each spring pass through Texas.
'That is a lot of birds,' says Brys. The Lights Out surveys take morning counts three times a week during the peak spring migration season – last year 295 mortalities were recorded. Volunteers have collected and tagged more than 100 species since 2020, including sparrows, doves, warblers, ovenbirds and more unusual finds such as a lazuli bunting or woodcocks, which are normally found in swamps.
But there is no way to fully count such deaths, Brys admits, because birds are so regularly thumping into office towers, homes, power lines and, to a lesser degree despite some claims, wind turbines. The losses compound – each killed songbird might make up to six nests a season, with as many as six eggs in each nest. 'So the loss of one bird is 340 or so birds within a two-year span,' Brys says.
For birds travelling from darker forests or grasslands, the sudden dazzle of lights and walls of glass found in cities can be a death trap. On maps charting US light pollution, Dallas is a burning beacon, sloshing light up and out of its buildings into the skies rather than focusing it on where it is needed. Most birds are nocturnal migrants, hardwired to navigate by the moon and stars, and the artificial replacements to these wayfinders, plus the reflections in glass, particularly of nearby trees that birds would aim for, cause many to become disoriented and crash into buildings.
'We had a security guard tell us that the birds run into the glass because they are effing stupid,' says Brys. 'And I said 'well, imagine trying to run through a mirror maze at 35mph, how far do you think you would get?' If we had never even seen glass before, how many people do you think would've walked into a glass door or window?'
Light pollution has been present since the lightbulb was invented but it's only in the past 20 years that glaring, intrusive light has started to routinely obscure the stars and imperil birds flying at night, according to Teznie Pugh, superintendent of the University of Texas's McDonald Observatory. 'It's become a major concern,' Pugh says. 'Each generation, we are basically halving the number of stars you're able to see at night.'
Globally, light pollution has increased by about 10% a year since 2011, a study released in 2023 found. But there has been some progress through a rethink of excess lighting, which is often costly as well as harmful, and the advance of bird-friendly glass, which incorporates dots or stripes to warn birds of an impending obstacle.
Cities such as Houston and New York have vowed to lessen bird strikes, with the latter altering its annual 9/11 tribute, in which twin shafts of light are thrown towards the heavens, by switching off the lights for a short period if more than 1,000 birds are trapped, befuddled, in its beams.
Chicago's McCormick Place, the largest convention centre in North America, became notorious when 1,000 birds slammed into it one night in 2023. 'That building is a real killer,' says Adriaan Dokter, an ecologist at the Cornell Lab of Ornithology. But the centre has since installed bird-safe glass, cutting the amount of crashes by about 90% last year.
In Dallas, Reunion Tower, a landmark that resembles a giant golf ball on a stick, has dimmed its lights during peak spring migration season and activists are piling pressure on the city's convention centre to take action too. The sprawling building has plenty of darkened glass at bird-flying height, unhelpfully situated near stands of trees. The centre is undergoing a renovation and the Lights Out volunteers are agitating for it to install bird-safe glass.
'Nobody wants to be the building that kills tonnes of birds and a lot of times it a simple solution such as to turn off your lights or use a curtain,' says Mei Ling Liu, a Lights Out organiser at the Texas Conservation Alliance.
Progress is complicated by ingrained habits of construction and lighting, exacerbated by LED lights, which are worse for birds and insects but are cheaper and more efficient. Bird-friendly glass also costs more than standard versions. 'It's a challenge,' adds Liu. 'When it comes to light pollution, it's not a single building issue, it's an entire city. And Dallas is still very bright.'
As Dallas starts to emerge from its slumber, the hi-vis wearing volunteers continue to find birds on their circuit. A warbler is discovered thrashing on the ground at the foot of a hotel – it is placed into a brown bag to be sent to a rehabilitation centre. A young, dead grackle isn't so lucky, nor is another bird, a splattered warbler, that Liu has to pick up with tongs and shake because it is covered in ants.
In all, 12 dead birds are recovered, placed in bags, logged and put into a freezer at the Perot museum, which installed bird-safe glass after some windows were smashed amid Black Lives Matter protests in 2020.
A sort of silent spring has enveloped avians, with three billion fewer birds in North America than there were in the 1970s, a loss that researchers have called 'staggering'. Around a third of US bird species are in need to critical conservation action, with numbers plummeting fastest in places where they are most abundant. 'That the declines are steepest in these stronghold areas is really striking and remarkable,' says Dokter. 'We are seeing birds disappear at a rate that, ecologically speaking, is super fast.'
The bald eagle and the California condor may have been saved from the brink of extinction but, more broadly, the days are marked by fewer birds now. Passenger pigeons, once so numerous they blotted out the sun while flying overhead, are completely wiped out.
Our world has fewer songs, less colour and a dwindling sense of wonder as a result. A toxic tangle of reasons are behind this feathered crisis – habitat loss, chemical use and the climate crisis among them – but the one that appears most solvable is the tragedy of birds crashing into buildings.
'The nice thing about this problem is that it's within our reach to change quickly, it's not like climate change or plastic pollution,' said Dokter. 'Bird-safe designs of windows are the future and more and more cities are realising issues with lighting. We can all influence this, even in our own homes. We can tackle this problem.'