Just found a CD with some material I wrote a long long long time ago.
EXT. DAY. PARK
Man sits on a park bench, he leans back and yawns
(Beat)
A pigeon shits in his mouth. The man swallows the runny pigeon poo, he wipes his mouth.
MAN (To pigeon)
Call me
END.
Thank God for brain development.
I believe this has great potential. The premise is excellent, and I loved the 'wipes his mouth' bit. Some of the lines could be discarded, as I don't think they add a lot to the overall comedic effect - unless of course, you want to develop it into a prime time BBC comedy.
Shit comedy (literally, not metaphorically) is something that I think has been overdone lately. I think you should concentrate on the park bench as it has more comic potential.
Having said that; I believe that this is a very funny, original sketch which had me laughing my socks off (metaphorically, not literally ) - although I would have liked to have heard less from the man and more from the pigeon. Other than that, you are definitely heading in the right direction with this one. Good luck.