In contrast, the idea of consciousness is something that isn't observable: self-awareness. I don't know that you're self-aware. I presume you're self-aware because I know that I am self-aware, and we're probably biologically similar enough that it makes more sense to presume your sentience than to presume your lack of sentience. Is self-awareness something that can only exist where intelligence exists? I think the answer is "probably," but I don't know.
Isn't the mirror test a way of determining if a creature has some degree of self-awareness?