As bird behavior goes, the displays of bowerbirds are among the weirdest. Male bowerbirds have taken up architecture to impress females, building large hutlike structures of twigs, decorated with shiny beetles, shells, and other colorful touches. Now, a new study shows that bowerbirds have substantially larger brains, compared to their body size, than other birds. It seems that building and appreciating designer follies has led to smarter birds.
To study the brain size of bowerbirds, zoologist Joah Madden of the University of Sheffield, United Kingdom, borrowed 70 stuffed specimens of various bowerbird species from one of Britain's largest bird museums, the Walter Rothschild Zoological Museum at Tring. He placed them under the x-ray machine of a friendly dental practice and took detailed measurements of their skulls. Using his data, he could calculate the original brain sizes.
As it turned out, bowerbirds have brains that are up to 80.6% larger than similar-sized birds of other families. Even within the bowerbirds, the species that build the more imaginative bowers have larger brains for their size than species that tend to cut corners. For example, Chlamydera cerviniventris, which constructs an elaborate avenue with two courts propped up on a raised stick platform, has brains 10% larger than Sericulus chrysocephalus, which puts up two bunches of twigs, scatters some shells, and leaves it at that. The results suggest that the wide variety of mental skills necessary for building complex bowers (such as having a mental image of what the bower should look like, or remembering where to find those nice red shells) may have caused the evolution of larger brains, Madden says.
Others argue that bowerbird skills may be comparable to human art to some extent. Evolutionary psychologist Geoffrey Miller of the London School of Economics claims that art and song are components of human courtship and have driven the evolution of our massive brains. "It is one of the few good models for human brain evolution," he says.