My horses are alive and well!
My birds free ranged for years and their favorite place to hang out was in the hay barn. Yep, that meant poop on the hay. I'd flick off what I could, but I know some got into the trough. I'd just trust my big girls not to eat it. And on the pasture, well, they eat around their own poop and dog poop, if you watch they're pretty selective with that lip what they gather up for a bite. I can't imaging they eat wild bird poop, or the poop from wild geese or ducks that frequent my pasture this time of year.
Like bobbi-j said, I think it all comes down to keeping your animals healthy to start with. Your birds aren't crowded, unless they're ill in some way I don't see it as a problem. Plus, they keep the flies down!