Abstract:  I examined the implications of paternal behavior for territoriality in passerines. Blue-headed vireos, Vireo solitarius, and Red-eyed vireos, V. olivaceous, display different breeding strategies. Blue-headed males demonstrate equal partnership with females in raising offspring, while Red-eyed males show a near absence of parental care.  Because testosterone inhibits parental care, it might be assumed that Blue-headed males possess lower levels of testosterone than Red-eyed males. Testosterone has also been shown to increase levels of song activity in males. Therefore, based on the previous assumption, it was hypothesized that Blue-headed males respond to other males with less song behavior than Red-eyed males. Song rate served as a measure of territorial response to conspecific playback in this study.  Baseline song rates were used to account for species differences. Two different conspecific song playbacks were used in an attempt to control for individual levels of dominance in male-male encounters.  No significant change in song rates occured in either species after both playbacks.  Red-eyed vireos demonstrated a disproportional response to playbacks, singing at a rate lower than the documented baseline.