ABSTRACT. Estrogen regulates reproductive behavior and drives the proliferation and differentiation of several cell types. These physiological functions of estrogen are mediated by estrogen receptors (ERs), and each ER isoform plays a distinct role. To clarify the molecular mechanism of estrogen action and to evaluate the effect of ERs on the secretion of ovalbumin (OVA) in pigeon oviduct epithelial cells (POECs), we determined the complete coding sequences encoding ER alpha (ERα) and ER beta (ERβ) in pigeons. The abundance of pigeon ERα and ERβ mRNA was detected using quantitative polymerase chain reaction. These results revealed that pigeon ERα is highly expressed in the oviduct, while pigeon ERb is highly expressed in the ovary and kidney. We hypothesize that ERα mRNA predominates over that of ERβ in the oviduct. The expression of ERα can be down- 1927©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (1): 1926-1937 (2014 Characterization and regulation of pigeon ERs regulated by 17β-estradiol, and the knockdown of ERα promoted OVA mRNA expression in cultured POECs, indicating that ERα may play an important role in OVA secretion.