Socialized sub-groups in a temporary stable Raven flock?
- 423 Downloads
A complex social life serves as one of the main driving forces behind the evolution of higher cognitive abilities in vertebrates. In birds, however, data are primarily derived from captive animals, which strongly contrast with free-flying birds in terms of the number of interaction partners as well as available space. In captivity, Common Raven Corvus corax, nonbreeder groups show strong social bonds and complex tactical manoeuvring, whereas wild non-breeders are thought to resemble anonymous aggregations. Over 2 years, we observed a free-flying population of Ravens that visits a game park in the northern Alps. We here focus on the daily fission–fusion dynamics, individual spacing, and the influence of spacing on the birds’ agonistic and affiliative behaviour. The composition of marked Ravens in the local population changed slowly but constantly, although often remaining stable for several weeks. Birds only flocked for feeding, mobbing and roosting, and spent the rest of the day in loose aggregations, characterised by temporary small subgroups of 2–5 individuals. Aggression was high during crowd foraging but low outside of a feeding context. Affiliative behaviours, such as sitting within reaching distance, allo-preening and social play, were observed particularly in the small subgroups. These findings suggest that Raven aggregations are not as unstructured as previously thought. Birds may spend time and/or interact affilliatively with multiple individuals during the day. This, along with temporary stability in group composition, provides the opportunity for social relationships to develop, and enables the existence of socialised subgroups within free-flying Raven aggregations.
KeywordsCommon Raven Fission–fusion dynamics Group life Complex societies Corvids
This work was financially supported from the FWF—Fonds zur Förderung der wissenschaftlichen Forschung (START: Y366-B17) and the DAAD—Deutscher Akademischer Austausch Dienst (D/07/44470), and we gratefully acknowledge the support provided by the Cumberland Gamepark and the Verein der Förderer der Konrad Lorenz Forschungsstelle. We thank Bernd Heinrich for interesting comments on an earlier draft of the manuscript. All experiments and bird manipulations comply with the current laws of Austria, and were authorized by the Central Administration of Upper Austria.
- Aureli F, Schaffner CM, Boesch C, Bearder SK, Call J, Chapman CA, Connor R, Di Fiore A, Dunbar RIM, Henzi SP, Holekamp K, Korstjens AH, Layton R, Lee P, Lehmann J, Manson JH, Ramos-Fernandez G, Strier KB, van Schaik CP (2008) Fission-fusion dynamics, new research frameworks. Curr Anthropol 49:627–654CrossRefGoogle Scholar
- Barrett L, Henzi P, Dunbar R (2003) Primate cognition: from ‘what now?’ to ‘what if?’ Trends Cogn Sci 7:494–497Google Scholar
- Byrne RW, Bates LA (2007a) Brain evolution: when is a group not a group? Curr Biol 17:R884Google Scholar
- Byrne RW, Whiten A (1988) Machiavellian intelligence. Social expertise and the evolution of intellect in monkeys, apes and humans. Oxford University Press, New YorkGoogle Scholar
- Caffrey C (2000) Marking crows. N Am Bird Bander 26:146–148Google Scholar
- de Waal FBM, Tyack PL (2003) Preface. In: de Waal FBM, Tyack PL (eds) Animal social complexity: intelligence, culture, and individualized societies. Harvard University Press, Cambridge, pp ix–xivGoogle Scholar
- Drack G, Kotrschal K (1995) Aktivitätsmuster und Spiel von freilebenden Kolkraben Corvus corax im inneren Almtal/Oberösterreich. Monticula 7:159–174Google Scholar
- Eklow A (1988) The behaviour of ravens Corvus corax, in fresh snow. Var Fagelvarld 47:89–90Google Scholar
- Haffer J (1993) Corvidae—Rabenvögel. In: Glutz von Blotzheim UN (ed) Handbuch der Vögel Mitteleuropas. Aula, Wiesbaden, pp 1947–2022Google Scholar
- Heinrich B (1989) Ravens in winter. Simon & Schuster, New YorkGoogle Scholar
- Huber B (1991) Bildung, Alterszusammensetzung und Sozialstruktur von Gruppen nichtbrütender Kolkraben (Corvus corax L.). Metelen Schr Natursch 2:45–59Google Scholar
- Rösner S, Selva N, Müller T, Pugacewicz E, Laudet F (2005) Raven Corvus corax ecology in a primeval temperate forest. In: Jerzak L, Kavanagh BP, Tryjanowski P (eds) Corvids of Poland. Bogucki Wyd, Nuak, Poznan, pp 385–405Google Scholar
- Smuts BB, Cheney DL, Seyfarth RM, Wrangham RW, Struhsaker TT (1987) Primate societies. University of Chicago Press, ChicagoGoogle Scholar
- Stiehl RB (1978) Aspects of the ecology of the common raven in Harney Basin, Oregon. PhD thesis, Portland State UniversityGoogle Scholar