Partner choice on the basis of an individual’s reliability is expected to stabilize social interactions. In this experiment, we tested whether carrion crows (Corvus corone corone) learn to differentiate between calls of reliable or unreliable individuals. Crows were kept in an aviary that comprised four visually but not acoustically isolated compartments, separated by a central room. In an association phase, a dead crow placed in the central compartment was visible only to one of the four crow groups, whilst alert calls of a conspecific were played back. Therefore, these calls were reliable for that group, but unreliable for the three other groups. The procedure was repeated, using a different reliable caller for each group. In two test sessions, 1 month apart, reliable and unreliable model individuals were played back, but no dead crow was presented. We quantified birds’ attention behaviour and the number of vocalisations emitted. In the association phase, crows were more attentive towards the reliable compared with the unreliable stimuli and called more in response to reliable compared to unreliable individuals. In the test and repeat phase, attention behaviour did not differ between reliability conditions, but the pattern of vocal behaviour reversed, with crows calling less frequent when listening to reliable compared with unreliable calls. Vocal responses of crows suggest that they can discriminate between reliable and unreliable callers.
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We thank Debbie Kelly and three anonymous reviewers for helpful comments on the manuscript. This work was supported by the Spanish Ministry of Economy and Competitiveness, project CGL2011-27260, to V. B.
Conflict of interest
The authors declare that they have no conflict of interest.
The authors declare that the study complies with the animal experimental regulations of Spain. Keeping of captive birds was authorised by the Regional Council of Castile and León (section zoology 005074), and study subjects remained housed in captivity before and after completion of the present study for further non-invasive observations and experiments.
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