Parental calls and nestling behavior in Tree Swallows

Parents in many passerines are reported to produce a vocalization at the nest that stimulates nestling begging. Although this phenomenon has been well documented, relatively few studies have systematically examined the use of this call. The purpose of our study was to examine the role of Tree Swallow (Tachycineta bicolor) contact calls in the stimulation of nestling begging. Both male and female Tree Swallows called proportionally more at early nestling stages when nestlings generally were less responsive to the arrival of their parent. Parents called more often before feeding than after, and females called on proportionally more visits in which they brought food than on brooding visits in which they did not bring food. Parents also called significantly more often after the first call if no nestlings begged than if one or more nestlings begged. Nestlings begged in response to contact calls given by parents at the nest and during experimental playbacks of contact calls. Our results suggest that one function of the Tree Swallow contact call is to stimulate begging.