As autumn begins across Missouri, so too does a symphony of nature sounds: the rustle of yellowing leaves, the last chirps of summertime bugs, the dull “thud” of a bird slamming into a window.
Research estimates around one billion birds, many of them songbirds on their southern migrations, die in the U.S. each year after colliding with buildings. Janet Haslerig, an avian ecologist with the Missouri Department of Conservation, said those kinds of collisions represent a significant threat to overall migratory bird populations.
“Unfortunately, glass is not a bird’s best friend,” Haslerig said.
During the day, windows can reflect the surrounding area, which birds perceive as an open space to fly or land. At night, they allow indoor light to bleed outside, which disrupts the dark skies and starlight birds use to navigate.
“It’s quite normal to humans, we know what glass is,” Haslerig said. “But this is kind of an artificial barrier for birds… they see reflections of vegetation, maybe a tree or bush, and mistakenly think that’s something they can fly through or onto. And unfortunately, it’s glass.”
Haslerig said there are many things people can do, whether they are a homeowner, renter or business owner, to make their glass more bird-friendly. Each strategy involves finding a way to break up those reflections, showing birds that there’s a barrier between them and the trees they think exist beyond your windows.
There are glass films, tape and paint that can be used to create a dot grid or pattern that — when applied on the exterior of a window — have been shown to reduce collisions. Closing the blinds or curtains at night during migration season also keeps artificial light from spilling outside and confusing birds.
“Birds are just pretty awesome,” Haslerig said. “We have quite a few birds here in Missouri — that breed here, that migrate through here — and we have so many artificial manmade barriers that we have created. I just think we need to do our part to protect those bird species.”
Light pollution, both from windows and from outdoor light fixtures, can be especially dangerous because songbirds use the moon and stars as a “compass” when flying south. Artificial lights can be a distraction — throwing birds off their path, leading them to collisions and exhaustion.
Vayujeet Ghokale is a professor of astronomy at Truman State University, and a board member of DarkSky Missouri, part of a nationwide organization dedicated to reducing light pollution. He said light pollution represents a problem across disciplines, from his own background in stargazing to human, plant and animal health.
“I came into this thinking of astronomy, the inability to see stars,” he said. “I’ve come to realize that the inability to see stars is a symptom of the problem, not the problem itself. The problem itself is that the indiscriminate use of outdoor lighting has brought about ecological and environmental issues.”
Ghokale said the national DarkSky organization worked with lighting engineers to develop five considerations for any potential sources of light pollution.
The first thing to determine: if the light is even necessary.
“Ask yourself, is the light useful? Do you really need to leave it on all night?” he said. “Sometimes the answer is yes, sometimes the answer is no. But at least ask that question to begin with.”
The second thing to consider is how the light will be directed. A light for your front porch, Ghokale said, should only be illuminating your front porch. Not “across the street into your neighbor’s window or yard, certainly not up into the sky, or into the forest or the park.”
Closing the blinds or curtains at night can help keep your indoor lights indoors, and getting a directional shade can make sure your outdoor lights stay where they’re needed.
Third, make sure the light is only as bright as it needs to be. As Ghokale said, “you don’t need stadium-level lighting” to cover your backyard. Fourth, DarkSky recommends attaching lights to motion sensors or automatic timers if possible, to make sure lights are only being used when they’re needed most.
The last thing to consider is what color the light will be. Warm-toned lights — amber, orange, yellow, red — are “least disruptive to your own circadian rhythm, and they’re least disruptive to other kinds of plants, animals, birds and pollinators,” Ghokale said.
Incorporating those five principles can help keep unnecessary light pollution from affecting all different parts of the ecosystem. In Ghokale’s view, there doesn’t need to be a conflict between our need for artificial light and the needs of animals.
“If we just kind of get our act together, we can get our security and our safety with well-directed lights, because this is not a zero-sum game,” he said. “Good, responsible lighting will be safer lighting, and really make your neighborhoods and communities safer, and it will benefit all these other living beings as well.”
For Haslerig, making simple, inexpensive changes to help migratory birds isn’t just an ecological imperative. It’s a way to acknowledge that “we can do a better job.”
“I think, just being good citizens, we can do a better job protecting birds and wildlife,” she said, “Just for the sake of doing the right thing… They have a lot they can give us, and we in turn can give back to them by protecting them.”
Fall migration in the central U.S. typically starts in early September and goes through late October. Resources such as the Cornell Ornithology Lab’s BirdCast give nightly updates on the number of birds passing through the state.
