It is difficult to distinguish between the eastern meadowlark and the western meadowlark based on their appearance alone, but then their calls are quite distinct. The whistle-like call of the eastern meadowlark can be easily distinguished from the flute-like call of its western cousin. This is an example of-

EVOLUTION OF A POPULATION

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

A	Temporal Isolation
B	Behavioral Isolation
C	Gene flow
D	Mutation

Explanation:

Detailed explanation-1: -Eastern and Western Meadowlarks are best separated by voice. For silent birds, look for darker head stripes and a mostly white (not yellow), mustache stripe on Eastern. They also show slightly more white in the tail in flight than Western.

Detailed explanation-2: -Western and Eastern meadowlarks look very similar and it is difficult to tell them apart, until they sing. Their mating songs are quite different. The Western meadowlark has a melodious song, whereas the song of the Eastern meadowlark sounds more like a whistle.

Detailed explanation-3: -Even though they look alike and have overlapping ranges, the western meadowlark, Sturnella magna (left), and the eastern meadowlark, Sternella neglecta (right), have distinctly different songs. As a result, they do not interbreed and are classified as separate species.

Detailed explanation-4: -Western meadowlarks do not respond to the mating calls of the eastern meadowlark, and vice versa. Because the two populations do not mate, they are no longer considered members of the same species. This type of isolation is an example of a pre-zygotic barrier because it prevents mating before the formation of a zygote.

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