Bonding beyond the pair in a monogamous bird: impact on social structure in adult rooks (Corvus frugilegus)
Résumé
The formation of social bonds outside the mated pair is not frequently reported in monogamous
birds, although it may be expected in some species like rooks, living in groups all year round. Here
we explore the social structure of captive adult rooks over three breeding seasons. We recorded
proximities and affiliations (i.e., allofeeding, allopreening, contact-sit) to classify relationships
according to their strength. Three categories of relationships emerged: primary (i.e., pairs), secondary
and weak relationships. Affiliations and sexual behaviours were not restricted to pairs, and
secondary relationships were clearly recognizable. Mixed-sex secondary relationships were qualitatively
equivalent to pairs (i.e., same behaviours in the same proportions), although they were
quantitatively less intense. Same sex pairs occurred, and were qualitatively equivalent to mixedsex
pairs. Overall we found that rooks social structure is more than just an aggregation of pairs,
which highlights the importance of considering extra-pair relationships in socially monogamous
birds.