Glass siding and atriums are increasingly used in green architecture, but they often have a deadly effect on our flying friends.

Building collision is the second highest cause of death for birds after habitat destruction, and one billion birds in the U.S. die every year from crashing into buildings. That's a whopping 5 percent of the country's total bird population.

The accidents occur because birds see mirror images of the outside world in glass reflections. Sometimes, they spot a desirable habitat or food source inside buildings and attempt to enter.

And this upsetting trend shows no sign of stopping—glass is becoming more popular among architects as its energy efficiency increases.

Even seemingly environmentally-friendly green roofs contribute to the issue, as they attract birds too close to glass.

A few concerned architects have found ways to lessen the problem— patterned glass, ceramic rods placed over glass—but these solutions are far from being widely adopted.

So before you decide to install those solar windows you've been pining after for so long, think of the birds.