Do nestling Tree Swallows (Tachycineta bicolor) respond to parental alarm calls?

Abstract

ABSTRACT Nestling birds use a conspicuous begging display, which includes loud begging calls, to solicit food from their parents. Although these calls are important in communicating offspring need, predators can use begging calls to locate nests. Parents may, however, counteract nestling vulnerability by giving alarm calls to silence calling nestlings when predators are nearby. This defense has been observed in grass- and reed-nesting species, whose nestlings beg to vibrational cues of a parent's arrival, even in the absence of the parents. It is considered less likely to occur, however, in cavity-nesting species, because the rigid substrate of the nest does not provide vibrational cues, and nestlings instead wait for a parental food call before begging. Cavity-nesting Tree Swallows (Tachycineta bicolor) use food calls to solicit begging, which suggests that parental alarm calls are not required to silence them. Older nestling Tree Swallows, however, beg in the absence of their parents, which suggests tha...