Glass windows are a marvel of ergonomics: transparent, nearly invisible sheets of durable material that allow natural light into enclosed buildings. But outside their light-filled, airy walls, windows become something else: a threat to wildlife.
Birds don’t understand glass. They’re not taught to recognize structural cues that indicate there’s glass, like a rectangular frame or a door handle. Instead, they’ll try to walk through the glass, seeing the open space behind the window as habitat or interpreting what they see in the glass as reality. Don’t judge birds too harshly for that. People also collide with glassBut for our winged, flying friends, the consequences are far more serious.
Combined with the attraction and disorientation caused by windows and glass buildings, especially artificial lighting, huge numbers of birds are dying. And the problem is even more serious than we thought. New research shows that previous estimates of the death toll are an underestimate. It may be tempting to think that all birds stunned or injured by windows and brought to wildlife rehabilitation facilities make a full recovery. But around 60% die. Even under the best circumstances, they are protected from predators and cared for, as the report outlines. the study Published in the journal on August 7th PLOS One.
Previous studies have come to mixed conclusions about estimates of bird losses from building collisions. One of the most commonly cited figures is: 2014 StudyAccording to the National Geographic, hundreds of millions to a billion birds die each year from window collisions in the United States alone. But this past analysis, and nearly all other studies of window mortality, relied solely on counting birds found dead on the sides of buildings. The new study goes a step further, assessing what happens to the portion of birds that survive the initial collision. The finding that more than half do not survive leads to a disturbing and disappointing revised estimate: “More than one billion birds die each year in the United States” from collisions with buildings, the study authors write.
“The numbers surprised me. I didn’t think it was that bad,” he said. Al Kornreichlead study author and biology doctoral candidate at Fordham University. “But unfortunately, it makes sense,” they say. Popular Science.
“Wild animals are tough. They try to survive in dire conditions for as long as they can… but we’re losing them even without seeing them,” Kornreich added.
Most birds that hit windows don’t die immediately. Recent observational studies They found that over 80% of birds that collide with glass fly away from the scene, 12-14% lose consciousness temporarily, and 50% of collisions leave no visible traces, but a new study demonstrates that many birds still die after impact.
Kornreich and his co-authors collected as much wildlife rehabilitation facility data as possible on bird building collisions in several Northeast and Mid-Atlantic states reported between 2016 and 2021, in accordance with the rehabilitation facility’s licensing requirements. Though their data has many gaps, they tracked over 3,100 recorded collisions involving 152 bird species. The researchers concluded that only 39.5% of birds brought to rehabilitation facilities after window collisions were released back into the wild after an average of 12 days or more of treatment. Conversely, 32.1% died during treatment, usually within three days of being found. An additional 28.4% of birds were euthanized by wildlife rehabilitation facilities, which determined that this was the most humane method for animals that could not be recovered.
“This study addresses an interesting and important question using an underutilized resource.” Travis LongcoreHe’s an urban ecologist at UCLA and the nonprofit’s scientific director. Urban Wildlands GroupLongcore, who was not involved in the new study but has studied light pollution and bird collisions with buildings, agreed with the new findings, saying: “Estimates of bird mortality from collisions are… teeth Probably on the low side.”
“When birds are stunned long enough to be captured and taken to a rehabilitation facility, even under the best of conditions — with food, water, no predators, and no street sweepers scooping them up or people trampling them — 60 percent will still die,” the conservation biologists say. Dustin Partridgestudy co-author and director of conservation and science at the NYC Bird Alliance.
Combining these statistics with birds that were excluded and found injured in a 2014 study on avian morality, the researchers conservatively estimate that about 100 million birds die from window collisions each year in the U.S. But these new figures are likely still an underestimate, because the birds found represent only a small fraction of the total number of birds that don’t die immediately after colliding with buildings, Partridge and Kornreich say.
“By studying rehabilitation cases, we can gain insight into hidden causes of death that aren’t apparent from carcasses,” Kornreich says, enhancing our ability to accurately estimate causes of death without having to count every single bird strike.
Many of the birds that aren’t seen stunned or taken to a rehabilitation center may still die. And those taken to rehabilitation centers may represent a more severely injured population than those that go unnoticed or quickly leave the crash site, Kornreich notes. “We don’t really know much about the birds that crash into windows and escape,” they say. More observation and follow-up is needed to determine long-term outcomes. And in general, there are a lot of unknowns and questions that this one study leaves unanswered. Their data is incomplete and regional. For example, it’s unclear whether these Northeast findings apply to other parts of the country, or what factors determine whether a bird ends up in a rehabilitation center.
But wild birds have proven difficult to survive, especially if they are injured or knocked unconscious — and the results are dire when you consider the percentage of birds that seem to bounce back after being injured in a window crash.
Additionally, the researchers assessed variables that influence the outcome of avian window collisions, finding that larger birds had higher survival rates, mortality and treatment times varied by season, and head trauma and concussion were the most commonly reported injuries, which may help inform and prioritize wildlife treatment in the future.
While they can’t save every bird that’s brought in, “wildlife rehabilitators are a lifeline for wildlife in need, not just birds,” Kornreich says. “They’re really part of the solution. They have a big impact on populations, but they also impact individual lives, which is valuable in and of itself.”
But the findings underscore that rehabilitation isn’t the only solution. “It drives home the fact that prevention is key,” Longcore said. teeth Possible.
Birds face a myriad of challenges in the modern world and their populations are declining rapidly, even some once-common species. 2019 Research North American bird extinctions are due to climate change, habitat loss, and of course cats. Feral and stray cats are to blame. 40 bird species go extinctand is considered the leading cause of human-caused bird deaths. One analysis estimates that cats kill 100% of birds. Up to 4 billion birds With 100 birds dying annually in the U.S., windows are a close second on the bird mortality charts, and window problems are probably the easiest of all the threats to deal with.
Proven strategies like bird-safe glass and retrofitting windows with film, tape, and properly applied stickers all minimize the risk of collisions with essentially no drawbacks. Many birds migrate at night and are attracted to the artificial lights of human cities, Longcore said. Efforts to turn off lights during migration season could prevent birds from being attracted to dangerous obstacles in the first place, saving millions of dollars.
Whether you live in an urban or rural area, everyone can play a role in helping. Because of the amount of space sprawl takes up and the predominance of low-density development, Longcore says, most bird collisions are likely to happen in suburban and rural areas with low-rise buildings and homes.
If you want to create a safer flying environment, “you need to let the birds see the glass,” says Partridge. Films or applications in patterns spaced up to 2 inches apart work best. Renovating existing windows“Screen screens are also a good preventative barrier,” he points out. And “turning off the lights is really important, especially during migration,” he adds. Turning off the lights in your home in the spring and fall and closing your curtains as soon as it gets dark are important personal steps. Lights out program Reforms for commercial buildings could bring about changes on a much larger scale.
“Birds are incredibly important to our environment,” Kornreich says, eating pests, pollinating plants, dispersing seeds, cleaning up carrion and more. Other Helpful ActivitiesBirds are also a joy: “For millennia, birds have provided inspiration and joy to humans,” they add. If we want to see birds flying in the distant future, we’ll have to change the way we think about our windows.