Yuck! I just witnessed mum (or dad -- although is he ever allowed in the box?) throw up one of those....pellet things of undigestible bird parts/bones etc....I don't know the name of it, but the equivalent of a cat hairball, I guess.
I wouldn't have watched except that I thought she looked like she was choking, or in some kind of distress and then I realized that she looks exactly like my cats do when they're about to throw up! And sure enough, that's what she did. Not to be too graphic or anything, but she looked at it for a moment, then kept opening, closing her mouth as if to say, "ew, that didn't taste very good!" , but like everything else, she's left it right there, right behind the chicks. They really don't mind what they're sitting in do they?!
Anyway that was another 'first' for me --- so much learning to do!