Help! Birds are crashing into my windows

The image of the afternoon sky is reflected into my windows. This week two female cardinals flew into my sunroom windows, breaking their necks. I need to do something about it. I'm not crazy about ugly (IMO) stickers or tape on my windows but if anyone has a suggestion I'm all ears. - Deborah

This is the latest idea that I've heard of. I have a couple, but don't need them. They look like you wouldn't see much, but birds are supposed to.
http://www.nixalite.com/windowalertdecal.aspx

I have those; they work very well.

Those are just what I need! Thanks for replying both of you! - Deborah