For the Birds: "Lights Out" Programs and the Avian Economy

Image credit: Billie Grace Ward / CC-BY-2.0
1096 words / 4-minute read

During the spring and fall bird migration seasons, volunteers with the Fatal Light Awareness Program (FLAP) fan out across Canadian cities. They collect the remains of birds that have died in collisions with buildings. For each bird found, they meticulously record information about the circumstances of its death. The birds are preserved for long-term study. Then, once a year, the volunteers meticulously lay out the bodies in public view. The Annual Bird Layout is FLAP's main awareness-raising event.

The results are sobering. Hundreds or even thousands of birds will die during one night in a single city. Bright urban lighting draws them away from their migratory routes. Some see light reflected in building windows and fly into what they think is clear air. Others circle until they drop dead from exhaustion. FLAP aims to document them all.

The space above and near cities is an invisible ecological superhighway. Billions of animals pass through this space each night. The Moon guides some of them, the stars others. City lights create a virtual deathtrap for these species. And it piles on other environmental stressors like climate change and habitat loss.

​One solution is to dim lights in cities during these mass migrations. According to this idea, dimmer cities draw fewer birds and lead to decreased carnage. Does the theory hold up in the face of evidence? Do seasonal light-dimming programs measurably save birds, or are they a feel-good form of "slacktivism"? This month we dig into the question and check the evidence.

The secret nighttime lives of birds

Migrating species like birds make connections between distant biomes. They move biomass, disperse plant seeds, and enable reproductive success. They also provide what ecologists refer to as "ecosystem services". These are the positive benefits that wildlife or ecosystems provide to people. They also connect is intimately to the natural world. Examples of ecosystem services provided by birds include agricultural pest control, maintaining natural plant diversity, and transporting essential organic nutrients. Humans can't do these things with any efficiency.

Artificial light at night (ALAN) interferes with this process. We previously wrote about how this adds to the sense of natural nighttime darkness as an object of conservation. The idea is that the value of these objects can elevate the level of attention society adds to them.

For example, much has been made of the notion of an ongoing, global "insect apocalypse". Declining pollinating insect populations could wreak havoc on food production worldwide. ALAN draws pollinating insects away from their target plants. Humans can't effectively replace their natural pollinating actions. In this way, ALAN becomes an issue of food security and even Indigenous sovereignty.

Light pollution is a primary predictor of where migrating birds land to rest. It unintentionally draws them into high-risk urban environments. There they find secondary threats like predators, vehicle strikes, and collisions with window glazing.

​One study identified skyglow as a top predictor of bird migration stopover density in over 70% of seasonal models. Another found that skyglow increased stopover density at regional scales near illuminated urban corridors. It creates ecological "traps" by altering the natural habitat selection of birds.

The science of "Lights Out"

​Reducing ALAN to lower its impacts on species sounds promising. Research using weather radar finds that ALAN actively lures migratory songbirds into dense urban centers. Turning off ground lighting breaks the disorienting "light trap". This allows birds to disperse within minutes and resume safe flight paths. Radar tracking during New York City's annual Tribute in Light demonstrates this best. Turning off high-intensity lights for 20 minutes allows thousands of trapped, circling songbirds to fly away.  

Migratory birds temporarily stuck in the World Trade Center "Tribute In Light" memorial display, New York City, U.S. (Source: Brian Tofte-Schumacher / CC-BY-SA-2.0)

Scientific data confirms that "Lights Out" initiatives yield immediate, quantifiable ecological benefits. They can also serve as gateways to essential municipal policy reforms.

Consider the results of even one such study. Analysis of 40 years of collision data at Chicago's McCormick Place convention center found that extinguishing window lighting reduced fatal bird collisions by about 60%. Halving the illuminated window area among buildings decreased collision counts by nearly 11 times. It didn't require any costly changes to buildings. It only asked building owners to turn out unnecessary lights.

​The data confirm that "Lights Out" programs are not mere "slacktivism". Turning off lights yields immediate, quantifiable reductions in avian mortality alongside energy savings. Although not a silver-bullet solution, campaigns can become an entry point for comprehensive urban conservation legislation.

Substantive or superficial?

But there are also some limitations to these efforts. The American Bird Conservancy points out that while dimming lights prevents night disorientation, it does not stop daytime glass collisions. Once light at night draws birds into a city, reflective glass remains the main threat the next morning regardless of night lighting. Policy advocates complain that voluntary programs suffer from inconsistent compliance. And building managers and municipal authorities sometimes resist the programs on public safety grounds.

Yet campaigners can push back on these objections. They can address the concerns by promoting the use of warmer-colored lights and adaptive lighting controls rather than complete blackouts. Reframing the issue away from "either/or" dichotomies respects the interests of diverse stakeholders.

​Critics say that "flipping a switch" is a passive solution. But it doesn't have to be. There are low-friction corporate and civic entry points for all "Lights Out" programs. Over time, these can build momentum for binding legislation and bird-friendly building codes. 

From symbolic action to structural solutions

The available science suggests that "Lights Out" programs work as advertised. Bird mortality declines without any obvious, negative effect on business operations or public safety. They can be paired with bird-friendly glass treatments for a more holistic approach, both day and night. Better nighttime lighting practices that align with the Five Principles for Responsible Outdoor Lighting can further reduce harm to birds.

Over time, these changes can be codified into law. Local lighting ordinances can enforce curfews, whether during migration season only or year-round. Bird-friendly lighting practices can be made part of local building codes. If carefully managed to avoid the phenomenon of "greenwashing", these programs can fit within broader ESG (Environmental, Social, and Governance) and sustainability frameworks. What's good for birds can be good for business, too.

​By preventing birds from becoming trapped in urban sinks, "Lights Out" initiatives preserve the healthy bird populations necessary to sustain essential ecosystem services. While not a panacea, they can be an important part of bird conservation programs. For now, campaigners are focusing on obtaining more voluntary cooperation as the pathway of least resistance. But as we learn more scientifically about the issue, the cause for making these actions obligatory may well only grow stronger.