The rock pipit and the water pipit are two types of birds found in the United
Kingdom and other areas of Europe. The rock pipit and the water pipit have similar
appearances and their habitat ranges overlap.
Which of the following observations most likely caused scientists to classify the birds as
separate species?
A. The rock pipit is not able to produce fertile offspring with the water pipit.
B. The rock pipit population in the United Kingdom is larger than the water pipit
population.
C. The rock pipit eats insects, fish, and seeds, but the water pipit eats only
insects and larvae.
D. The rock pipit remains in the United Kingdom year-round, but the water pipit
only overwinters there.