Amberlee, we have hummingbirds all the time at the window - they see themselves in the window glasss. I read somewhere that they consider it a rival bird, and often they charge at their reflection and bang against the window, sometimes with tragic results.

We actually witnessed one hitting the window so hard that it died instantly. These pretty little hover birds are quite agressive!

I had an outdoor kitty once who caught a hummingbird while it was visiting the feeder! I wouldn't have believed it if two of us didn't see it happen. It was partly because the hummingbird was in one of these territorial battles with another bird and was shoved into the path of the kitty, who was poised and ready!