Well, one way is if they aren't capable of reproducing, then they cannot be the same kind.
But the birds in question cannot reproduce so how come they are the same kind?
And theoretically an a chimp/human hybrid is possible so are we the same kind?
Like I said, though, its going to depend on how much micro-evolution is possible. If it isn't possible for the two types to have evolved from a common ancestor, then they must be different kinds.
So we are all the same kind??
And by your definition it is impossible to produce a new kind because it would always have a common ancestor no matter how different it looks, or how large the genetic barrier it has to its cousins or ancestors that make it impossible for it to reproduce with them.
Edited by frako, : No reason given.
Edited by frako, : No reason given.