Bird-friendly yards have a major downside — for birds

Many homeowners go out of their way to make their yards friendly to birds. They plant vegetation or install feeders and birdhouses — and battle the squirrels that try to take advantage of that generosity. But what seems like a good deed for nature may be luring some birds to their deaths, a new study finds.

The birds are dying from collisions with building windows. Scientists have estimated that between 365 million and 988 million birds die each year in the United States from colliding with windows, Science News reported in 2014. And nearly half of those deaths occur from collisions with homes and other buildings that are three stories tall or less. But researchers haven’t been able to say what makes one home more deadly than another.

Justine Kummer of the University of Alberta in Edmonton, Canada, and colleagues turned to citizen science to find patterns in bird deaths in residential neighborhoods in Alberta. They asked volunteers living in homes and apartment buildings to survey the perimeter of their homes, looking for birds that may have collided with one of the windows.

The team accumulated the equivalent of 34,114 days of monitoring data from their citizen scientists, who had observed 930 collisions and 102 bird deaths. There were three factors that increased the likelihood that a collision would occur: location in a rural setting, the height of the yard’s vegetation and the presence of a birdfeeder. Such attributes make the landscape more attractive to birds, the researchers note, and the more birds that are around, the more likely that a collision with a window will occur. The researchers report their findings  in the August issue of the Condor .

Eliminating birdfeeders would seem like an easy solution to this problem, but it wouldn’t really do much to stop these collisions, the scientists say, since the birds are attracted to other aspects of a home’s yard. And we don’t necessarily want to keep birds out of our yards anyway — they are pleasant to have around, and providing habitat for nature is generally a good thing. Plus, no one can yet say whether the numbers of birds killed in window collisions is having an effect on bird populations.

The solution, then, lies in altering windows so that birds stop flying into them. The researchers found some evidence that birds were more likely to fly into windows that reflected vegetation and into windows that have energy-efficient coatings, which are more reflective than regular glass. Decreasing the reflectivity of these windows or installing some kind of deterrent may be able to reduce collisions.

And this is something that scientists are now working on (Science News highlighted this research in 2013). They have come up with patterns and types of glass that register to birds as something solid, not an extension of the landscape. But there are also simple solutions that can help, such as putting up a screen or closing exterior shutters.

Don’t bother putting up a cutout of a predatory bird, like a hawk, though. While this may seem an easy way to keep a bird away, it doesn’t work.