The marker can be anything - a dot, zigzag, checkerboard - but it does have to be applied uniformly on the window at space intervals of no more than four inches up and down.
"It's a tight enough space that the bird can still see the reflection," Mesure explains. "They can still see what's on the other side of that glass. But they go, 'You know what, I can't fit through that space. It's too tight for me to feel I can slide through without bashing into something. I'm going to fly around it.'"
And the results are obvious.
"As you start to slowly increase that space between those markers, the strikes slowly but surely start to increase," he says.