Google "Guano". I remembered from history class how merchants became very rich importing birdsh*t to use as a very effective natural fertiliser. Made a fortune! Forget the "problem" CAPITALISE on your mis-'fortune'? "This time next year Rodney - We'll be millionaires!" (Only Fools & Horses - Brit sitcom)
I was able to get the birds out of the tent with an air horn and then shutting the front bay door. They ended up moving to the smoking area and have done this: I will be looking for some way to poison them now. Death to all Afghan birds, I call for Jihad!
A think a disco ball with lights aimed at it would do the trick. Have you also got a white suit, I'm sure throwing some moves would frighten them away.
Closing the bay door was working, now they just come in earlier than I am allowed to shut them. No disco balls to be found at the bazaar here. Unfortunately I haven't ran across any poison yet.