Avian nests are frequently concealed or camouflaged, but a number of species builds noticeable nests or use conspicuous materials for nest decoration. In territorial species decorations may serve as extended phenotypic signaling of nest-site occupancy and social status to potential intruders. The latter may benefit both signaler and receiver by minimizing the risk of aggressive interactions. Here, it was tested whether nest decorations increased nest-site visibility to conspecifics in black...

Many theoretical models on the evolution of nestling begging assume this behavior is costly, so that only nestlings in real need of food would profit from giving intensive signals to parents. However, evidence accumulated for the last 2 decades is either contradictory (growth costs) or scant (immunological cost). Here, the existence of both costs is experimentally tested in pied flycatcher nestlings.