Answer:
Their different mating rituals separate the two populations.
Step-by-step explanation:
likely the correct answer because the fact that the two populations of bowerbirds have "almost identical genes" suggests that they are closely related, but are unable to breed with each other. This is most likely due to the fact that they have developed different mating rituals, which includes building different types of bowers and decorating them with different colors. This difference in mating rituals would make it unlikely for the two populations to breed, as the females of each population would be attracted to the bowers and decorations that are specific to their own population.