Endocrine systems have an important mechanistic role in structuring life-history trade-offs. During breeding, individual variation in
prolactin (PRL) and
corticosterone (
CORT) levels affects behavioral and physiological processes that drive trade-offs between reproduction and self-maintenance. We examined patterns in baseline (BL) and stress induced (SI; level following a standard capture-restraint protocol) levels of PRL and
CORT for breeding mourning doves (Zenaida macroura). We determined whether the relationship of adult condition and parental effort to
hormone levels in wild birds was consistent with life-history predictions. Both BL PRL and BL
CORT level in adults were positively related to nestling weight at early nestling ages, consistent with the prediction of a positive relationship of
hormone levels to current parental effort of adults and associated increased energy demand. Results are consistent with the two
hormones acting together at baseline levels to limit negative effects of
CORT on reproduction while maintaining beneficial effects such as increased foraging for nestling feeding. Our data did not support predictions that SI responses would vary in response to nestling or adult condition. The magnitude of
CORT response in the parents to our capture-restraint protocol was negatively
correlated with subsequent parental effort.
Average nestling weights for adults with the highest SI
CORT response were on
average 10-15% lighter than expected for their age in follow-up
visits after the stress event. Our results demonstrated a relationship between individual
hormone levels and within population variation in parental effort and suggested that
hormonal control plays an important role in structuring reproductive decisions for mourning doves.
