I get that the changing weather might change their habitual latitudes but there was and is always some "boundary" between the two, no? So there was always a boundary but it moves north or south depending on warming or cooling climates (these birds have been around for millions of years). How did they only mate now?
I get that the changing weather might change their habitual latitudes but there was and is always some "boundary" between the two, no? So there was always a boundary but it moves north or south depending on warming or cooling climates (these birds have been around for millions of years). How did they only mate now?