Abstract: Monogamous songbirds display elevated levels of T prior to nest building, and levels drop as reproduction progresses, with marked differences between the sexes. Elevated T is an attractive trait in the male dark-eyed junco, however development of elevated T throughout the breeding season may be constrained if T is genetically correlated between the sexes, and imposes a fitness cost to females. We addressed the question of costs of elevated T in females by examining both behavioral and physiological measurements in a captive population of dark-eyed juncos (Junco hyemalis) during the breeding season. We found no significant difference in daily activity behaviors, however, T females vocalized chacks, a distress signal, more often than C birds. Females displayed Ptiloerections (feather puff-up) more often, and this behavior was correlated with male LRS, and female wing fluttering. There was no difference of male courtship behaviors. T females displayed a less robust cell-mediated immune response to a challenge of an innocuous protein, but treatments did not differ in either season long mass change or condition change.