An Enclosed Nest Can Increase the Risk of Predation on Adults

Even though enclosed nests provide a physical barrier for cavity-nesting birds, nest predation is the primary cause of breeding failure and a major driver of avian population dynamics. Previous studies have largely focused on the loss of eggs and nestlings, whereas the predation risk faced by adult birds during the nestling-rearing stage has received far less attention. We recently documented a predation event in which an Amur rat snake (Elaphe schrenckii) remained concealed in a nest box after consuming nestlings of the Daurian Redstart (Phoenicurus auroreus) and captured a returning male. This observation provides empirical evidence for understanding predation risks in enclosed nesting environments and suggests that adult mortality may warrant consideration in predation risk assessment. Additional observations are needed to determine whether similar predation events occur in other cavity-nesting systems.