Members of the same species of bird became geographically separated. Over many years, the two groups evolved to become two different species. Which of these observations is the best evidence that two separate species developed?

More information required

Explanation:

Is there a picture you forgot to post with the question?

In the problem you mention, which I assume comes from the study of finches in the Galapagos, some birds evolved to have different beaks, depending on the food available. Depending on what kind of seeds there are, different beak sizes were selected for, with those with the right fit eventually winning out over the rest on the individual islands.