Part of the tests, therefore, involve spreading lines or visual cues out farther to see when they no longer deter birds. Mr. Haffey said that vertical lines are believed to work best at four inches apart, while horizontal lines need to be spaced every two inches.
"We're going to see how far we can stretch the limits," Mr. Haffey said. "The fewer lines you have on the glass, the happier the architects are going to be."
"But if it means saving that many birds, we can stand the occasional eyesore."