The best method I've ever come across to discourage bird strikes is taping
thin ribbon onto the window, or alternatively, stringing the ribbon randomly
on hooks or nails top to bottom. I've used this on several houses I've
lived in. Taping will let the ribbon flutter, but the stringing seems to be
as effective-- perhaps something in bird perception registers the vertical
pattern as obstruction?
I got 1/8-1/4" wide ribbon on spools (it is inexpensive), in several colors
because I like color and what the heck, if you're going to put ribbon on the
outside of the windows, might as well be festive about it. The ribbon is
thin enough that it does not interfere with the view from inside and looks
cheerful from the outside. Though I have to admit my neighbors were quite
puzzled until I explained...
I imagine surveyers line might work too, but wouldn't be as fun.