Vocal identity and information content in the flight initiation calls of greylag geese (Anser anser)

Vocal signals are used to convey information in environments and over distances where signals of other modalities would fall short. Some of the information that they contain concerns the individual identity and class membership, allowing receivers to assess their familiarity, relationship and past experiences with each signaller. Calls are known to function in social cohesion contexts among others, notably in gregarious birds, where staying with the group has an adaptive value. Greylag geese produce two seemingly distinct call types during their flight initiation signalling; the ‘Locomotion call’ and the ‘Pre-flight call’. We analysed the acoustic structure of both call types to first investigate whether these two call types differ acoustically. Second, we explored the presence of vocal cues to individual and class-level information (sex, age, breeding status and relatedness). Our results showed that the two calls were spectrally distinct. In addition, each call type contained information about individuality and sex-class membership, but not about age or breeding status. These results suggest that the Locomotion and Pre-flight calls of greylag geese carry information reflecting multiple facets of caller identity, potentially allowing familiar conspecifics to characterise their interactants even at a distance and in acoustically rich contexts.