Question

What happened to the greenish warbler birds as they migrated from the southern portion of their range up around the Tibetan Plateau?

Answer 1

a.
They evolved separately as they moved north and became two separate species.
b.
The original species died off, but the ones that were able to adapt to a northern climate evolved into a new species.
c.
As a whole the species was able to adapt to a colder climate, but no significant changes occurred.
d.
They were unable to adapt and evolve to ensure their survival and became extinct.

Answer 2

i guess its c