The eastern meadowlark and the western meadowlark are two bird species that look very similar to each other. Why do biologists not consider them the same species

The question is incomplete as it does not have the options which are:

The two species experience the reproductive barrier of habitat isolation. Species are not determined by appearance but by their ability to interbreed naturally. The two species do not live in the same habitat and thus do not interbreed in nature. All of the above are correct.

Answer:

The two species do not live in the same habitat and thus do not interbreed in nature.

Explanation:

According to the most widely accepted concept of biological species, a species is considered a species if it is able to interbreed among the individuals and produces viable offsprings.

In the given question, it is clear that meadowlark lives in the eastern and western part of the country therefore they are separated by the geological barriers and are reproductively isolated. Therefore they do not mate and produce a viable organism and thus are not considered species.

Thus, the selected option is correct.