Functional Interrelationships Among the Mobbing and Alarm Caws of Common Crows (Corvus brachyrhynchos)

Abstract

Abstract and SummaryThis study is an analysis of the functions of calls used by common crows (Corvus brachyrhynchos) in contexts involving danger. Four types of calls (screams, mixed caws, inflected alarm caws, alert caws) were tape recorded and played back to 7 captive crows. Three types of vocal response (mixed caws, alert caws, long caws) were scored for the 3 most responsive receivers. From the magnitude and temporal course of the responses, and from comparison of the various responses across the different playback types, functional interrelationships among caw types were found. Mixed caw responses showed a single pattern of elicitation only in response to certain playback types, and were inferred to be unifunctional (indicating immediate danger). Alert and long caw responses showed different patterns of suppression and elicitation with respect to playback type, and were inferred to be multifunctional (indicating mild danger; cessation of danger; business as usual; intraspecific aggression). These results are discussed in terms of the information encoded in mobbing and alarm calls, and their functional and adaptive significance.