Elaborate courtship displays in birds are not uncommon and can be as simple as having fancy plumage to performing acrobatic acts to try to attract birds of the opposite gender. In male birds, testosterone binding to androgen receptors is a driving force for these courtship displays. It was unknown, however, whether testosterone is able to directly act on muscle tissues.
Researchers Feng et al., studied the expression pattern of the androgen receptors in the muscles of golden-collared manakins, a bird with very athletic courtship behaviors as seen in this video. They compared the manakins to zebra finches and ochre-bellied flycatchers that do not perform athletic courtship displays. What they found was that, compared to these other birds, the limb muscles of manakins had greater gene expression of androgen receptors. In fact, the levels were higher in the muscles than in the testes or brain. Moreover, manakins had higher concentrations of an enzyme that activates testosterone. These findings support the author's conclusion that testosterone can act directly on skeletal muscle during courtship displays.
Photo Credit: Â© Mike Danzenbaker
Feng NY, Katz A, Day LB, Barske J, Schlinger BA. Limb Muscles Are Androgen Targets in an Acrobatic Tropical Bird. Endocrinology. 151: 1042-1049, 2010.