Offspring provisioning effort in European starlings (Sturnus vulgaris) during the nestling rearing period

Abstract

Rearing offspring is a critical but energetically costly period for birds. Socially monogamous species typically have biparental care, although females invest more heavily in the offspring. Some studies have found that in the socially monogamous yet facultatively polygynous European starling (Sturnus vulgaris), females provisioned the offspring at similar rates as the males, with provisioning rates higher in the mornings than the afternoons. One study also found that provisioning rates tended to increase mid-way through the nestling cycle before declining. This study was conducted to confirm whether the findings in the literature also pertain to our European starling population. Parental provisioning by eight European starling pairs was studied over the nestling period using GoPro cameras. Two observation sessions (morning, afternoon) per pair were done on five different days through the nestling period. I predicted that male and females would provision offspring at a similar rate. I also predicted that offspring provisioning rates would be higher in the mornings than afternoons. Finally, I predicted that as nestlings aged, provisioning visits would increase. Females provisioned offspring significantly more often than males. Moreover, parents provisioned at higher rates in the mornings than afternoons. Finally, as nestlings aged, provisioning rates continued to increase. This study has implications in further understanding avian investment in offspring provisioning behaviours.