Widespread accumulation of [H-3]testosterone in the spinal cord of a wild bird with an elaborate courtship display

Elaborate courtship displays are relatively common features of the masculin e reproductive behavior in birds. However, little is known about their neur al and hormonal control. One bird that performs such a display is the golde n-collared manakin (Manacus vitellinus) of Panamanian forests. Adult males, but not females, perform a physically intense display requiring substantia l neuromuscular control of the wings and legs. We tested the hypothesis tha t steroid sensitivity is a property of neurons in the manakin spinal cord. Males and females were captured from active courtship leks, treated with dr ugs to block steroidogenesis, injected with H-3-labeled testosterone, and t he spinal cords were removed and processed for autoradiography. Sex steroid -accumulating cells mere widely distributed in the spinal cords in each of six males and in one of five females, Cells, including presumptive motoneur ons, reached their highest density in the ventral horns of the cervical and lumbosacral enlargements, regions associated with motor control of the win gs and legs. These results suggest that neurons in the adult manakin spinal cord can express sex-steroid receptors, but do so less in females than in males. This evidence for androgen sensitivity and sexual dimorphism in the adult avian spinal cord suggests that sex steroids may control diverse beha viors in male birds in part by acting directly on the spinal neural circuit s.