Buildings are one of the top bird killers in the United States, with more than a billion birds dying after a building crash each year. About 60% of birds brought to wildlife rehabilitators or emergency rooms for animals die while in care of the facility either by succumbing to their injuries or euthanasia, according to a new study released in the Public Library of Science Journal on Wednesday. 

There has been a widespread bird population decline in North America over the past half-century. The North American bird population is down by nearly 3 billion birds since 1970 according to a Cornell Lab study, making addressing hazards to bird ecosystems more urgent. 

The injured birds are often brought to wildlife rehabilitation centers with head trauma and concussions. The bigger the bird, the more likely it was that it would recover and be released back into the wild. The rehabilitation centers examined in the study found that they received the greatest number of bird patients in the fall with the least number of admissions in the winter. 

But even when the best care is provided, there is only a 40% chance of recovery for the injured birds. 

Glass is a major culprit in bird collisions. Unlike humans, birds cannot view visual cues differentiating glass from the open air. Birds see the reflection off glass and go straight ahead into what they view as either open skies or a potential habitat, and birds see the reflection of nearby green space in windows as more vegetation. Buildings with curved surfaces rather than flat surfaces have been shown to have a greater number of bird collisions. 

But there are ways that people can help prevent bird-building crashes. 

“We cannot rely on only rehabilitation to fix this kind of problem,” said Ar Kornreich, lead author of the study and researcher at Fordham University Graduate School of Arts and Sciences. “The best medicine is absolutely prevention because some of these injuries just have really bad prognosis.” 

One at-home remedy is to put tape on windows at least 2 inches by 4 inches apart, so birds do not think they can fly through the window, said Kaitlyn Parkins, glass collisions program coordinator at the American Bird Conservancy. ABC BirdTape, for example, is a translucent tape that can be applied on the outside of the glass in stripes or squares to prevent bird collisions. 

Installing bird screens or window decals are other ways to divert birds from hitting windows. 

“Birds are in extremely steep population declines,” said Parkins. “Birds are really important to humans. They are economically important, and they provide ecosystem services for us. And window collisions are contributing to that population decline. So it’s really important that we all take steps to prevent collisions.”