When I was at one my wife's friend's house this summer for a BBQ, I noticed that they had a lot of bird sh|t all over their house and patio furniture. It was disgusting!
Anyhow, as I was enjoying a beer and playing horseshoes, I noticed that there were a bunch of sparrows flying around an old barn that was adjacent to the the back yard. I watched at least three or four of those bastards fly towards the yard, drop their load, and then turn back from whence they came... all in a period of about 15 minutes.
So, yes, they do aim...