Put a cat up there.
No..... Are tehy pooping right on the LNB lens? I thought those were hooded.
Just went and looked at mine. A bird sitting on the top of dish would not be able to hit the LNB. Although they COULD get the dish itself and the LNB arm. You can PAINT a dish and not hurt it it. So my guess is that a little bit of bird droppings shouldn't be detrimental.... except it probably looks like ... well..... anyways.... rain SHOULD wash it off sufficiently.
If you have pigeons or something up there all the time and there's a real buildup happening, you might have issues. Is it that bad?