The Danger of Clean Windows???

Until I pulled a muscle in my back a few days ago, I was running around like crazy trying to get the house ready for my parents 50th wedding anniversary party this weekend.  I've been touching up paint, having the guys change out lights, spot cleaning the carpets, and other things like that.  
I've never been a real stickler for spotless windows, but I do like them to be clean.   Around here, the wind blows so much and dust flies everywhere, so nothing stays clean for long.  Unfortunately, the birds around here must be used to the spots on my windows.  We have bird feeders in the tree outside our living room windows so we spend a lot of time watching the birds.  Yesterday, a bird flew straight into the living room window.  It hit so hard that the windows shook.  I'm shocked that the glass didn't shatter into a thousand pieces.  We still have feathers on the window!  
I think I'll let this be a lesson to me.  Keep the spots on the windows and save the birds.