Dirtiest animals in the world

Last week, I walked up to Donato's and picked up a pizza for lunch. On my way back to the office, I saw some pigeons up ahead fighting for something on the sidewalk. I get closer and realize it's somebody's yack. Those things were going to town on it. I almost lost it right then and there. Finally, the light turned green and after I crossed the street, I saw some more pigeons up ahead. They were eating what appeared to be another pile of spew chunks. I think it was two different people. One pile was orange and one was brown. I thought, "Oh man, I'm not going to be able to eat now." But as soon as I sat down, I devoured what must have been half of a large pizza. I guess it didn't bother me that much. I think if I would have had another bite, I would have been feeding the pigeons too.