"Not a Zoo but I worked at a local science centre as a part time guide, and one of our most popular exhibit was this incubator with baby chicks. We were told to tell visitors that the older baby chicks would be sent to schools as classroom pets or to the petting zoo.
In reality, we did sent the chicks to the Zoo… As live animal feed for the snakes and other carnviores."
dyslexic_draws
You have never lived on a boat with wild birds overhead in masse, because some birds can definately choose WHEN they go. For survival they can release before flight, to gross out a predator, or mark territory/flight path. Or they can hold it near their nests to avoid attracting attention. No animal as evolved as a bird would leave pooping up to pure chance.