Neuroendocrine regulation of reproductive behavior in birds

This chapter reviews the neural and endocrine basis of reproductive behaviors in birds with a particular focus on the role played by gonadal sex steroid hormones in the regulation of sexual behaviors. Studies of birds continue to be valuable for the elucidation of the neuroendocrine control of behavior. The avian brain also exhibits a remarkable degree of hormone-regulated neuroplasticity in associated neural circuits. Work on the neuroendocrine control of avian male sexual behavior has identified the key role played by estrogenic as well as androgenic metabolites of testosterone acting in the preoptic region to facilitate behavioral activation. Estrogenic metabolites of testosterone have relatively slow actions (i.e., days to weeks) that are often genomic in nature as well as relatively fast effects (e.g., minutes) that result from actions at the cell membrane. These different modes of action are associated with different temporal modes of the regulation of the enzyme aromatase (that converts testosterone to estradiol) in the brain. Female sexual behavior is activated by ovarian estrogens acting in the ventromedial nucleus of the hypothalamus. Parental care is hormonally primed in females by synergistic actions of sex steroids and prolactin while males tend to respond to cues provided by females.