In three species of Australian bowerbirds the volumes of several brain structures were determined based on areal measurements of fixed tissue. Allometric comparisons, i.e., those that take into account the gross interspecies and intersexual differences in body mass and overall size, were made among these three species. Sexual dimorphisms were detected in the vocal control nuclei of each species. Most intriguingly, a putatively novel nucleus in the dorsal hyperstriatum of all three species has been identified. These findings are discussed in a functional context, in which the bower-building habits of these three species of bowerbird are considered.