Birds migrate to move from areas of low or decreasing resources to areas of high or increasing ones. The two primary resources being sought are food and nesting locations. But migration is a risky and exhausting time in the lives of birds; some migrate hundreds or even thousands of miles.
Nearly 1,000 birds were killed in Chicago on October 4, 2023, when they collided with an illuminated glass building. Though mass fatalities of this magnitude are rare, light pollution poses a serious—and growing—threat to migrating birds.
We need birds. Not only do they eat insects that plague crops and gardens—providing free pest control—they pollinate plants and distribute seeds. They act as cleanup crews by eating the dead bodies of other animals. They stimulate economies just by being beautiful. In an economic analysis released in 2009, the U.S. Fish and Wildlife Service calculated that, based on a 2006 survey, birders spend $12 billion annually on travel, plus an additional $24 billion on equipment like binoculars, camping gear and nest boxes. That money ripples through the economy and generates $82 billion in output, employs 671,000 people, and enriches state and federal governments by $10 billion.
Birds also help with our mental health. A new study shows that people who have nature-based experiences report better well-being and lower psychological distress than those who do not. And bird-watching, especially, yielded exceptional results, with higher gains in subjective well-being and more reduction in distress than more generic exposures to nature, such as walks.
In one new study, bird-watchers, especially, gained in feelings of well-being and had a greater reduction in distress than even those who engaged in nature walks.
Luckily, bird-watching is an easily accessible activity. And now, another new study is providing information on how we can plan urban areas that favor biodiversity and public well-being—through designs that attract birds.
The lure of artificial light
Migration is a risky and exhausting time in a bird’s life. Birds migrate hundreds to thousands of miles—sometimes burning half their body mass along the way. Finding a good place to rest and refuel is critical for surviving and thriving once the birds reach their final destinations.
Recently, in the largest study of its kind—published in the journal Nature Communications in December 2023—scientists used weather radar data to map bird stopover density in the United States. By pairing more than 10 million weather surveillance radar network observations with landscape and other place-based information, the scientists tried to explain why birds choose certain rest stops. They discovered that out of 49 predictors, artificial light pollution was the number two predictor of stopover density. The top predictor was elevation. That could be because the patterns created by migrating birds that are picked up by radar tend to follow coastlines or a particular elevation. So, light pollution is the top predictor of human influence on bird migration.
City lights cause birds to collide with buildings and lure them into areas with less habitat, scarcer food, and more people and cats.
That artificial-light lure is extremely detrimental to birds. Nighttime city lights entice birds into what can be an ecological trap, with buildings that lead to collisions, places that have less habitat and scarcer food, and spaces filled with more people and cats, making urban areas less-than-ideal rest stops. While metropolitan parks can be decent stopover sites, birds that rest there might need to compete for limited resources.
This notable study provided the first continent-wide maps of migration stopover hot spots in the contiguous United States. Knowing these broadscale layover patterns leads to a conservation conundrum: should urban centers be conserved as important stopover locations or targeted for lights-out campaigns?
Urban lighting involves lots of stakeholders, making it a complicated issue. There can be social pressure to leave lights on, and some people find them aesthetically pleasing. But light pollution not only harms birds, it can hurt people, too. When human circadian rhythms get disrupted, it can lead to health problems, including cancer, cardiovascular disease, depression and insomnia.
Stopover locations—such as this one on a Texas lake—are fueling stations for migrating birds like American white pelicans. If they don’t find good spots to rebuild their energy supplies, migration can’t happen.
Tools like BirdCast—a collaborative project from Colorado State University, the Cornell Lab of Ornithology and the University of Massachusetts Amherst—can help. BirdCast provides migration forecasts and real-time maps from weather radar. Anyone can create alerts to be notified when birds are flocking near a particular city. Forecasts pinpoint which nights are most important for reducing light pollution.
Retrofitting windows with decals, such as gridded dots or lines, can help prevent collisions by revealing the barrier to birds. Lowering the brightness and softening the color of lights can help, too. Bright white or blue lights are the worst for wildlife, while warmer hues—such as orange, red and yellow—are less attractive. Communication towers used to beam continuous white lights to warn aircraft. Birds would circle the towers, hitting the wires that secured them. In 2016, based on conservation research, the Federal Aviation Administration started requiring communication towers to use flashing red lights, dramatically reducing bird collisions.
The Chicago McCormick Place Convention Center collisions that killed nearly 1,000 birds (most of the 33 species tallied were songbirds) in October 2023 might be an extreme example of birds dying because of light pollution, but mass fatalities involving 100 or more birds are all too common. It is estimated that nearly 1 billion birds strike buildings in the United States every year.
For birds, glass windows are worse than invisible. By reflecting foliage or sky, they look like inviting places to fly into. And because the sheer number of windows is so great, their toll on birds is huge—about 1 billion birds die from window strikes in the U.S. each year. Decals or stickers placed on the outside surface of windows and spaced very closely to cover most of the glass can help deter birds.
Public awareness of migration habits would be a good place to start to help protect birds from light pollution, conclude the researchers. Most people might not realize that birds migrate at night. For such a complicated problem, this one has a simple solution: if we turned off all lights tonight, there would be no birds colliding into buildings because of the glare.
The configuration of green spaces
Land-sharing urban development is a term that describes maintained, small green areas, usually in the form of private gardens and street vegetation, interspersed with single-family buildings and low population density. In contrast, land-sparing urban development is characterized by large green areas (usually large gardens and parks) that are clearly separated from built-up spaces, which are densely populated and contain apartment blocks.
To learn which of these urban designs appeals to species with certain types of traits, an international team of scientists—including researchers from the University of Granada and the National Museum of Natural Sciences—studied the distribution of 115 species of birds in spring and 72 that spend the winter in nine European cities, including Prague in the Czech Republic and Granada, Madrid and Toledo in Spain.
Birds control pests naturally; they eat insects that plague crops and gardens.
For each species identified in the European cities that were studied, characteristics such as the effort invested in breeding, the degree of feeding specialization, longevity and the type of nests built were quantified. The findings, published in the journal Science of the Total Environment in January 2024, showed that land-sparing urban areas are breeding grounds for birds that lay many eggs, use open nests more frequently and have short life cycles, such as stonechats, chiffchaffs and crested larks. In contrast, land-sharing urban areas are dominated by birds with more demanding breeding requirements and longer life cycles, such as great tits, kestrels and gulls.
The results of this study demonstrate the need to promote a mix of both types of urban development to allow for greater bird diversity, which is not only beneficial for our immediate environment but also for our own health and well-being.
The benefit of bird presence
Here’s another reason why we need birds: for college students seeking to improve their mental health, a potential answer may be right outside their windows. It’s bird-watching.
Kestrels favor “land-sharing urban development,” which is characterized by small green spaces—such as private gardens and street vegetation—interspersed with single-family buildings with low population density.
A new study, published in the Journal of Environmental Psychology in June 2024, finds that people who have nature-based experiences report better well-being and lower psychological distress than those who do not. Bird-watchers, in particular, showed higher gains in subjective well-being and more reduction in distress than those who engaged in more generic nature activities, such as walks.
Because becoming a bird-watcher is relatively easy—it’s among the most ubiquitous ways that human beings interact with wildlife globally—the results are encouraging for college students, who are among those most likely to suffer from mental health problems and who live on school campuses where there’s plenty of access to the activity, even in urban settings.
To quantitatively measure subjective well-being in this study, researchers used a five-question survey known as the World Health Organization-Five Well-Being Index (WHO-5). This tool asks participants to assign a rating of zero through five to statements about well-being, depending on how often they have felt that way in the last two weeks. For example, given the prompt “I have felt calm and relaxed,” a participant would mark a zero for “at no time” or a five for “all of the time.” Researchers can calculate a raw well-being score by simply adding the five responses, with zero being the worst possible and 25 the best possible quality of life.
Today, adolescents and college-aged kids are struggling the most with mental health problems. Bird-watching is an easily accessible activity that has been shown to result in better well-being and lower psychological distress.
The participants were split into three groups: a control group, a group assigned five nature walks and a group assigned five, 30-minute bird-watching sessions. While all three groups had improved WHO-5 scores, the bird-watchers started lower and ended higher than the other two. Using STOP-D, a similar questionnaire designed to measure psychological distress, researchers also found that participants in both the bird-watching and nature-walking groups showed more declines in distress than the control group.
This study differed from some previous research, in that it compared the effects of bird-watching and nature engagement to a control group rather than a group experiencing more actively negative circumstances. For example, one of the studies reviewed in the paper compared people who listen to birds to people who listened to the sounds of traffic, which isn’t a neutral comparison.
The results support the idea that bird-watching helps improve mental health and opens many avenues for future research, such as examining why bird-watching helps people feel better.
Being in nature looking for birds helps you focus on the sights and sounds around you, making it less likely that you’ll dwell on your concerns and worries. This can help lower your cortisol levels, the hormone associated with stress.
The foretelling of feathered ones
In addition to all the other benefits and ecosystem services that birds provide, they are an important indicator for environmental health because they are sensitive to habitat change and are easy to count. Birds integrate and accumulate environmental stresses over time because they are usually high in the food chain and have relatively long lifespans. Like the canaries in the coal mines, birds are our early-warning system, as when declining numbers and breeding success of birds such as bald eagles, brown pelicans and ospreys revealed that DDT was a pollution hazard.
Birds have also been part of human culture since prehistoric times, when they appeared in early cave paintings and rock etchings. Today, they still play diverse and prominent roles in our folklore, popular culture and religions.
Humans have caused the extinction of about 1,400 bird species throughout modern human history. Today, there are more than 11,000 species of birds on Earth. But approximately 1,200 of them (or 11%) are considered endangered, threatened or vulnerable.
Birds have been part of human culture since prehistoric times. This image of a bird is found in Wyoming’s Legend Rocks State Petroglyph Site, a sacred place for the region’s Native Americans for thousands of years.
I believe that if all the birds disappeared, our crops would fail, economies would crash, forests would wane, insects and rodents would overrun us, and food supplies would diminish.
Most of all, our skies would look graceless and empty.
And all songs would be sad.
Here’s to finding your true places and natural habitats,
Candy
