European Starling (Sturnus vulgaris) parents call less often as their nestlings age

We analyzed recordings made in nest boxes of 7 early-season and 4 late-season broods across four nestling ages (days 2, 4, 11, 13) to determine whether parents called when arriving at the nest box and whether the other parent was in the box or not. We predicted that parents would call more often when nestlings were young (days 2, 4) than when they were older (days 11, 13). If calls were directed to nestlings, then we predicted that calling would be unrelated to whether the other parent was in the nest box.

If calls were directed to their mate, we predicted that calling would be positively related to the other parent being in the nest box. As predicted, parents called significantly more often when nestlings were young than when older, although parents reduced their calling earlier (day 4) in late-season broods. We found that parents were more likely to call when the other parent was in the nest than when they were not.

Our results suggest that the intended recipient of calls is likely the other parent rather than the nestlings. Flexible communication at the nest would be adaptive as parents call when nestlings are young to likely increase parental coordination and thus provisioning efficiency and stop calling when nestlings are older as it is no longer required and could be costly in terms of predation risk.