Wood warblers learn to recognize mobbing calls of an unfamiliar species from heterospecific tutors

Abstract

Mobbing, a collective harassment of a predator by multiple prey species, is ubiquitous in animals. In birds, it is often prompted by specific vocalizations (mobbing calls) produced by an individual that detects a predator; this attracts nearby conspecifics and heterospecifics in a joint assault on the predator. Mutual recognition of mobbing calls among heterospecifics, even those distantly related, is widespread in birds and learning appears important for its acquisition and maintenance. Yet, the evidence for learned recognition is mostly indirect and the specific learning mechanisms remain largely unknown. Here, I provide experimental evidence that free-living birds (wood warblers, Phylloscopus sibilatrix) can learn to recognize novel heterospecific mobbing calls through interspecific social learning, by associating mobbing calls of a previously unknown species with those of the already recognized heterospecifics during joint mobbing events. Moreover, individuals retained the learned recognition of novel mobbing calls over at least 2 weeks. These results illustrate interspecific social learning as one of the mechanisms underlying the widespread mutual recognition of mobbing calls among bird species. This mechanism of learning is likely to be common in the wild, enabling naïve individuals to utilize a wide set of possible information sources, and result in a rapid cultural transmission of novel antipredator signal recognition within avian communities.