It takes a seasoned bird to be a good listener: communication between the sexes

• Extreme diversity in avian vocal behavior enables rich comparative work on neural and behavioral mechanisms.
• Both male and female songbirds can learn to produce and perceive vocalizations.
• In birds where only males sing, the sexes differ in the morphology of pre-motor but not auditory nuclei.
• Steroid sex hormones influence both pre-motor and auditory activity.
• Sex differences in auditory responses result from elevated estrogens in seasonally breeding females.

Birds commonly use sound for communication between the sexes. In many songbird species, only males sing and there are pronounced sex differences in the neural song control circuits. By contrast, the auditory circuitry is largely similar in males and females. Both sexes learn to recognize vocalizations heard as juveniles and this shapes auditory response selectivity. Mating vocalizations are restricted to the breeding season, when sex steroid levels are elevated. Auditory cells, from the ear to the cortex, are hormone sensitive. Estrogens are synthesized in the brain and can modulate the activity of auditory neurons. In species that breed seasonally, elevated levels of estradiol in females transiently enhance their auditory responses to conspecific vocalizations, resulting in sex differences in audition.