The Social Context of Contact Calls by Rooks (Corvus Frugilegus)

Abstract


 
 
 Communication is the link between individuals of one species and represents the essence of social life. Vocal communication is one of the most studied forms of information exchange, although it also comes with interspecific barriers that are still tricky to overcome. While we are able to understand the meaning of another human’s words, we fail to understand an animal’s utterances. Among these, bird song has become a field of particular interest. However, little is known yet about many species’ vocalizations, and even less about their significance or how different factors influence them. The presented study establishes the vocal repertoire of a group of rooks and further investigates the importance of contact calls between partners in an experiment. We found that test subjects and other group members produced more contact calls after than before partners had been separated from each other, indicating stress induced by physical isolation and/or the lack of visual contact as an important factor influencing the call frequency. Separating certain individuals seemed to affect the group differently, which indicates that the ‘importance’ of the animal to the group influences the group call rate. In this study, we have shown how social and environmental factors play a role in vocal communication in birds.
 
 

Vocal complexity in a socially complex corvid: gradation, diversity and lack of common call repertoire in male rooks

“…In the majority of vocal species, a vocal repertoire is composed in majority by clusters reflecting different call types, with some degree of gradation potentially present, but we found large degrees of gradation that precluded segregation into call types, especially for female call units. Finally, the vast majority of call units in this study could not be conclusively associated with specific behaviour contexts, which is consistent with other literature on corvid vocal communication [45][46][47]. However, one particular call type could be conclusively associated with a behavioural context: the nest call, produced only by brooding females.…”

“…We may therefore expect their repertoire to exhibit very high levels of diversity or flexibility that allow this identity signalling. At the group level, rooks possess a medium to large repertoire of calls [ 45 , 46 ], with evidence of an individual vocal signature in the most common ‘caw’ call unit produced by males [ 23 ]. Like several other corvids, they can also mimic other sounds, including anecdotal evidence of human voice mimicry [ 41 , 43 , 47 ] (N.S.C.…”