Helping enhances multiple components of reproductive success in the cooperatively breeding apostlebird

Abstract

1. We examined the influence of helpers on reproductive success in the apostlebird using data gathered over three breeding seasons (116 nests, 34 breeding groups). Initially, annual productivity and individual components of reproductive success were examined in relation to group size (two to 17 birds). The effect of helping per se was then examined in a reduced data set by comparing (a) the predictive power of group size and actual helper numbers, and/or (b) the productivity of groups that changed in size between nests or seasons. 2. Group size was positively and linearly related to annual fledgling production and the number of offspring that survived to the following season. This was attrib..