Grouseness
Grouse are “adapted” not merely to an environment, but also to being grouse. There is something remarkably grouse-like in their overall design, many constituent parts, and in each of their responses to stimuli. They even seem to know that they are grouse; to be contented with that identity, willing to live and even die in the condition of being grouse.
One may make no sense whatever if one takes them to be something else. They will persist in being grouse-like, and in point of fact grouse, even if we try to persuade that they are, say, cockatoos.
Some other creature may invade their peculiar environmental niche; might even do so successfully. The grouse will respond to that invasion implacably, as grouse. They will under no circumstances attempt to transform or metamorphose themselves in reaction to such an existential crisis. Indeed, they will not consider such a proposition. It is always strictly fight or flight, on unambiguously grouse terms.
They will, if shot by a hunter, even taste like grouse.
Should they flee, it will be to the sort of territory that they find agreeable to themselves, as grouse. They will even go in search of such locations, should that prove necessary. But finding no such territory, they would frankly rather starve than cease being grouse.
It would take a miracle for a grouse to develop or “evolve” some new characteristic. For as I’ve said, it would never occur to the grouse themselves. More likely it would occur to the Grouse Angel — the being assigned by God to look out for grouse interests. Yet even in such a case, the new character would emerge from the underlying grouse-ness of the former character, and appear as an extension of the grouse repertoire. It would be all of a piece with their ontology.