The definition of what constitutes a species is a human construct.
Two bird populations living in the same locale but divided by a mountain range therefore not naturally breeding with each other would classify as a different species, even if they could breed with each other.
So your question is hard to answer.
> Two bird populations living in the same locale but divided by a mountain range therefore not naturally breeding with each other would classify as a different species, even if they could breed with each other.
Really? I thought the requirements for species classification were: (1) must be able to reproduce and (2) offspring must be fertile.
Is it less objective than that?
I’ve often dreamt of breeding with that mythical bird far, far away.