Parental behavior correlates to baseline corticosterone of mates and offspring in nesting eastern bluebirds (Sialia sialis)

• Parental feeding behaviors were scored during nestling care period.
• Baseline corticosterone was measured in males, females and nestlings.
• Nestling corticosterone positively correlates to feeding rates of both parents.
• Maternal, but not paternal, corticosterone correlates to nestling corticosterone.
• Male feeding behavior correlates to female corticosterone, not own corticosterone.

Raising nestlings in a biparental species involves a complex and dynamic interaction of physiology and behavior among a group of organisms. Parents may be predicted to vary their behaviors based not only upon their own state, but also in relation to the states of both offspring and the other parent. In this study we explore the relationships between parental feeding behaviors and family member condition in eastern bluebirds, with a special emphasis on baseline corticosterone, a hormone associated with energy mediation and stress. We found that the overall number of feeding trips made by both male and female parents were positively correlated to the corticosterone levels of nestlings. Maternal, but not paternal, baseline corticosterone levels were positively correlated to nestling baseline corticosterone levels. Additionally, adult males’ feeding behavior was positively correlated to adult females’ baseline corticosterone levels. These findings suggest a complex interplay between parental behavior and physiological state not only within a given organism, but also across organisms operating within a family unit. In addition, these results provide evidence that paternal and maternal efforts are influenced by related but distinct pressures, and that male and female parenting may be governed differentially even in species with relatively equitable biparental care.