Effects of estrogens during embryonal development on crowing in the domestic fowl

In the domestic fowl, crowing is typically a male-specific vocal behavior while the females normally do not crow. These sex differences in vocalization may result from organizational actions of estrogens during specific periods of embryonic development. To further investigate the role of estrogens in differentiation of crowing and development of the acoustic characteristics of crow calls, male domestic fowls were treated on Incubation Day 8 with estradiol benzoate (EB) or either oil or saline vehicles. On the same incubation day, the female fowls were treated with an aromatase inhibitor, fadrozole, or saline vehicle. An adulthood vocalization of cocks and hens was recorded during corresponding tests of sexual behavior. The exposure to EB or fadrozole had no effect on sexual differentiation of the gonads and all fadrozole-treated hens laid eggs at a rate similar to the control hens that received saline. While the levels of plasma testosterone at adulthood did not differ in treated and untreated cocks, the incidence of crowing rate was significantly lower in cocks that were exposed to estradiol. Acoustic analysis revealed a considerable reduction in duration and acoustic energy of calls while the main frequency characteristics were not changed. Four out of the seven tested fadrozole-treated hens demonstrated regularly crow-like vocalization with shorter duration and lower energy of calls in comparison to crows of the control males. These findings point out to a role for estradiol in organization of crowing behavior and a specific temporal pattern of the crowing call.