Estrogen has organizational and activational effects in birds. Females require estrogen for development of reproductive anatomy and courtship and reproductive behaviors of both sexes are associated with estrogen levels. Therefore, exogenous estrogen exposure may significantly change physiology and behavior. 17&alpha-Ethinylestradiol (EE2), a synthetic estrogen in oral contraceptives, is ubiquitous in wastewater effluents. EE2 exposure is known to alter avian embryonic development, but activational effects on adults are not well studied. We tested the potential for EE2 to disrupt reproductive success through effects on male courtship behavior of zebra finches (Taeniopygia guttata). We used three EE2 doses, 0 ng (control); 4 ng, which is a concentration found in streams near wastewater effluent sites; and 100 ng, which serves as a positive control. Males were dosed orally every other day for three weeks prior to courtship trials continuing until nestlings hatched or for up to six weeks after pairing, if no eggs were laid. We recorded male and female courtship behaviors to test whether the time required to initiate pair bond behaviors was affected by EE2 treatment. Measures of nesting success included number of eggs laid, number of young hatched, nestling growth, and nestling survival to fledging. In courtship trials, EE2 treated males were less likely to mount females than controls but took less time to initiate pair bond formation via clumping behavior than controls. Preliminary data suggest that EE2 exposure of males may also influence nesting success of the pair. These results demonstrate significant evidence that environmentally relevant EE2 exposure in adulthood influences avian behavior and reproductive success.