Male bowerbirds construct elaborately decorated nests, or bowers. Basing their judgment on

A. There are more common characteristics than there are differences among the bower-building styles of the local bowerbird population that has been studied most extensively.
B. Young male bowerbirds are inept at bower-building and apparently spend years watching their elders before becoming accomplished in the local bower style.
C. The bowers of one species of bowerbird lack the towers and ornamentation characteristic of the bowers of most other species of bowerbird.
D. Bowerbirds are found only in New Guinea and Australia, where local populations of the birds apparently seldom have contact with one another.
E. It is well known that the song dialects of some songbirds are learned rather than transmitted genetically.