Responses to acoustic competition among conspecifics has been studied extensively in the context of male-male sexual competition -- in orthopterans, anurans, and birds, for example -- but has been relatively neglected in other situations. We recorded the begging calls of nestling tree swallows, Tachycineta bicolor, that were exposed to silence (control), the calls of nestlings deprived of food for 30-50 minutes (low hunger) or the calls of nest mates deprived of food for 100-110 minutes (high hunger). Nestlings gave longer bouts of calling when exposed to low hunger calls, but surprisingly did not in response to high hunger calls; indeed, they delayed the onset of their calling in the latter treatment. Thus nestlings escalate their calling in response to calling by nest mates, but only at moderate levels of nest mate calling; at higher levels, nestlings appear to, in effect, "give up." Whether they do so to yield to a hungrier nest mate or instead to let that nest mate do the work of stimulating higher parental feeding rates is unclear. Moreover, analysis of the timing of their calls suggests that, at high levels of nest mate calling, nestlings might switch from calling for longer than their nest mate to instead timing their calls to avoid overlapping them with those of the nest mate. Certainly the results show that calling interactions among nestlings do not simply consist of escalations in call output, as often assumed.