A comparative analysis of courtship movements in closely allied bowerbirds of the genus Chlamydera. American Museum novitates ; no. 1936

8 p. : ill. ; 24 cm.Includes bibliographical references (p. 8)."A comparative analysis of the courtship movements of two closely related allied species of bowerbirds is presented. One male of a dimorphic species, the great gray bowerbird (Chlamydera nuchalis), possesses a bright nuchal crest; the other, belonging to a monomorphic species, has no crest. Both were observed to display with the back of the head turned towards the female in an awkward manner, apparently intended to show the crest. The crested species displayed vigorously with the crest and to a minor degree with ornaments held in the bill; the crestless species displayed vestigially with the non-existent crest and then vigorously with ornaments held in the bill. The hypothesis is advanced that the vestigial head-twisting movements indicate that the crest has been secondarily lost as a result of the transfer of sexual signaling from sexual plumage to sexual objects. This hypothesis is presented as a second line of evidence for the transferral theory, a theory, based on an examination of study skins and of bowers, that presumes to account for the inverse ratio existing between the development of sexual plumage and the development of the bowers in certain species of the Ptilonorhynchidae"--P. 7