Why does the bowerbird engage in such complicated, time-consuming, and exhausting mating rituals? No one is entirely sure. One theory is that, in contrast to species like the peacock, where the male has very distinct and visible coloration to attract mates, the bowerbird keeps its nuptial colours external, thus making it easier for the male to hide from predators. This makes a certain amount of sense for species like the great bowerbird (lowest image), perhaps, but not for others like the regent bowerbird (center image). Some studies suggest that it is a way for the female to judge the male’s health; the male bowerbird’s plumage and colours may indicate that he is free from internal parasites, while the bower itself may show a lack of external parasites.
Perhaps the most interesting theory, however, is that the bower may have begun as a way of preventing forced copulations, and thereby reassuring the female of her choice of mates. During courtship by the male in the bower, the female often stands under a constructed archway or roof, thereby preventing the male from mounting her unless she moves. Evidence for this theory is seen in different species of bowerbird; The Archbold’s bowerbird, for instance, does not construct a true bower, but their courtship has been heavily modified so that the male cannot mount the female without her cooperation. In contrast, the toothbilled bowerbird also does not construct a bower, and males have been seen forcibly copulating with females by attacking them in the air.