PARENTAL CALLS AND NESTLING BEHAVIOR IN TREE SWALLOWS

Parents in many passerines are reported to produce a vocalization at t he nest that stimulates nestling begging. Although this phenomenon has been well documented, relatively few studies have systematically exam ined the use of this call, The purpose of our study was to examine the role of Tree Swallow (Tachycineta bicolor) contact calls in the stimu lation 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 mo re often before feeding than after, and females called on proportional ly more visits in which they brought food than on brooding visits in w hich they did not bring food. Parents also called significantly more o ften after the first call if no nestlings begged than if one or more n estlings begged. Nestlings begged in response to contact calls given b y parents at the nest and during experimental playbacks of contact cal ls. Our results suggest that one function of the Tree Swallow contact call is to stimulate begging.