Calling in the Face of Danger: Predation Risk and Acoustic Communication by Parent Birds and Their Of fspring

Birds raise their young under constant risk of predation, which shapes how parents and young communicate acoustically. Nestling begging calls extract care from parents but expose them to eavesdropping by predators, which selects for cryptic signal design. However, for largely unknown reasons, nestlings often call even when parents are absent and thus unavailable for defense. Nestlings can give distress and defensive calls, but their efficacy is unknown. Parental alarm calls warn young of danger in some species, and young can show adaptive changes in response according to their age-related vulnerability to specific predators. Parents often signal their arrival at the nest with provisioning calls, which might reduce mistaken begging and increase the efficiency of feeding, and thereby minimize detection by predators. Acoustic interactions between offspring and parents can lead to young either remaining silent until prompted by a parent's provisioning call, or begging indiscriminately to subtle cues of arrival while remaining alert to parental alarm calls. Young can also assess danger independently of parents, which could in turn affect parental decisions about giving alarm calls. All these behaviors offer fertile ground for studying how animals trade off acoustic communication with the risk of eavesdropping.