Yeah, experts say that hawk silhouettes don't work. They also say that owls don't work for birds that live in the area (hence, the blue jay), as they get used to the fact that it doesn't move, so it's not "real". In this case, the owl is used to drive migratory birds, so it's actually effective.
The UV products near the bottom are supposed to be quite good, but I've not tested them yet. I've heard that 3M is coming out with a UV film product that should be even better, but I can't seem to find it right now.
no subject
Should you have the cardinal issue again, look into one of these options: http://www.birdwatchingdaily.com/featured-stories/15-products-that-prevent-windows-strikes/
The UV products near the bottom are supposed to be quite good, but I've not tested them yet. I've heard that 3M is coming out with a UV film product that should be even better, but I can't seem to find it right now.