When the henshed was a henshed it had doors and/or windows on all sides bar one. We made a window on that side so I would have the evening light. An unforseen consequence of this is that the birds can see straight through and therefore think that they can fly straight through. We've had a dead woodpecker, blackbird and a stunned bluetit. I hung a makeshift curtain up to prevent any furthur casualties but really didn't want to go down the curtain/blind/shutter path if possible. This is what we've tried then - masking the windows and painting them with opaque laquer. I hope it'll break the light up enough to alert the birds...

Still in painting mode, today I masked a rectangle on the wall over my desk and painted it with magnetic paint - Weird! I've still got another couple of coats to put on. Does it work?