AGONISTIC COMMUNICATION IN SOCIAL SPECIES - WHAT IS COMMUNICATED

Relationships between displays used in agonistic encounters, the next behaviour of the reactor, and the actor’s subsequent response, are analysed in captive siskins (Carduelis spinus). A three-way independence test showed that the different displays are associated with different replys. Factorial Analysis of Correspondences showed that 76% of the variability in the displays could be explained by variation in the tolerance of the actor to the presence of conspecifics: certain displays led to submissive or non-aggressive responses by the reactor which led to non-aggressive behaviours by the actor, whereas others frequently provoqued an attack, which usually led to a retaliatory attack by the actor. The degree of caution in the response appears to be the other factor that modulates the reactor’s subsequent response. This degree of caution appears to be directly related to the relative dominance status of the contestants. These results support the view that in highly social species the aim of agonistic displays is not necessarily to drive opponents away, since this may be costly for both contestants. Agonistic communication in these situations should not be seen as an “auction” to determine who will obtain the resource, but as a warning, in which the actor gives information on how tolerant it is to the close presence of the conspecific and what behaviours it will allow. Depending on its status and behaviour, the second bird may be tolerated, but if it behaves in a “dangerous” way, the actor would attack. © 1990, E.J. Brill, Leiden. All rights reserved.