Natural variation in circulating testosterone does not predict nestling provisioning rates in the northern cardinal, Cardinalis cardinalis

摘要: Behavioural transitions between territoriality and parental care are necessary for many seasonally breeding vertebrates. Among birds, such can be mediated by the steroid hormone testosterone (T), resulting in a T-mediated behavioural trade-off. This theory is supported implantation studies with birds demonstrating that administration of exogenous T during phases negatively affect offspring care. However, little known about relationships naturally circulating levels behaviour wild bird populations. We examined covariation (before after injection gonadotropin-releasing (GnRH)) nestling provisioning rates male female northern cardinals, Cardinalis cardinalis, highly aggressive, biparental resident songbird. Results indicate both sexes had detectable initial when providing care, but only males produced significantly higher elevations following GnRH injections. Furthermore, (both injections) did not covary either sex, these measures were correlated members pairs. When results this study considered prior work indicating might to support or aggression species, it appears reproductive could more complex cardinal than others similarly examined. Such findings warrant additional examination interrelationships T, other forms assess whether species engages trade-offs. Possible alternative mechanisms influencing future directions research discussed.