Two Bird Species Overlap in a Hybrid Zone

Multiple Choice

Two bird species overlap in a hybrid zone. They are isolated by a slight difference in the male songs and by the females' tendency to select males with the "correct" song. Hybrid offspring tend to have reduced fertility compared to either of the parent species. What effect might natural selection have in this situation?

A) Natural selection might favor males with less distinctive calls and/or females that are less "choosy."
B) Natural selection might favor males with more distinctive calls and/or females that are more "choosy." As a result, the reproductive barrier between the two species could be reinforced.
C) Natural selection could lead to the hybrid species taking over and eliminating the weaker parent species.
D) Natural selection could lead to the stronger of the two species taking over and eliminating the other species.