Hegel says that we can tell that nature is not the domain of the rational because there are lots of different kinds of birds, whereas in itself the concept would necessitate only one bird. I think about this all the time

just for example (EN §370 z): nature is unavoidably full of externalities, imperfections, contingency; it has no inner necessity, cannot be properly systematized; nature is the unresolved contradiction, the diremption of the concept. all of which sucks obv