Are Androgens Related to Aggression in House Wrens?

Elevated circulating testosterone levels are hypothesized to allow male animals to direct resources into territorial and mating behaviors at the expense of reducing paternal care of offspring. For this hypothesis to apply, testosterone must facilitate territorial/mating behaviors and have antagonistic effects on paternal care, but this pattern has only been supported in some, not all, species. I tested whether androgens correlate with aggressive behaviors in male house wrens ( T roglodytes aedon ), a double‐brooded species where paternal and aggressive behaviors overlap temporally. House wrens may therefore benefit from having a hormonal mechanism that allows males to rapidly change behavioral states. However, I found no evidence that androgens (testosterone and 5α‐dihydrotestosterone) relate to aggression in house wrens: Androgens did not increase in response to playback, and endogenous‐circulating androgens were not correlated with how aggressively males responded to those playbacks. Moreover, androgen levels were low during the pre‐breeding stage of the second brood, when many males establish new territories and attract new mates. This study adds to a growing body of the literature suggesting that the relationship between circulating androgens and aggressive behavior is more complex than originally thought.