Summary
The formation of groups at food bonanzas results from a variety of mechanism, which include recruitment by signalling and information parasitism. Recruitment is distinguished from information parasitism on functional grounds: attraction of a crowd is termed recruitment if the signaler's fitness is enhanced by the attraction of others but termed parasitism if the signaler's fitness is reduced by the attraction of others. We here show, however, that in Common Ravens, Corvus corax, the proximate reasons for giving recruitment signals are probably other than for attracting a crowd. In the forests of the northeastern United States, non-breeding, vagrant ravens commonly aggregate in large numbers at carcasses where they neutralize the defense of territorial adults. We attempted to mimic this situation with a captive flock of juveniles and a pair of resident adults in order to determine the proximate factors triggering “yells”, vocalizations which attract nearby ravens to large animal carcasses. Our experiments indicate that yells are given primarily by hungry birds. However, yelling is strongly modified by status. Within the vagrant crowd, status is labile. When successive dominants were removed, replacements immediately took their place. Furthermore, when the dominants were re-introduced to the flock they always suffered significant losses of status and ceased yelling. The territorial male has, and constantly maintains, the highest status within (but not necessarily outside) his territory, and here he rarely yells. In sharp contrast, within the vagrant crowd of unmated birds it is the highest-status birds that are the most likely to yell when approaching food. Furthermore, the dominant vagrants (as well as adults) suppress yelling in subordinates. We conclude that ravens yell proximately to advertise their status at food, and that recruitment is only one of several ultimate advantages of the behavior.
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References
Altman J (1974) Observational study of behavior: sampling methods. Behaviour 49: 227–267
Appleby MC (1983) The probability of linearity in hierarchies. Anim Behav 31: 600–608
Balda RP, Bateman GC (1974) Flocking and annual cycle of the pinon jay, Gymnorhinus cyanocephalus. Condor 73: 287–302
Brown C (1986) Cliff swallow colonies as information centers. Science NY 234: 83–85
Bruggers JD (1988) The behavior and ecology of the common raven in Northeastern Minnesota. PhD thesis, University of Minnesota, Minneapolis
Chapman CA, Lefebvre L (1990) Manipulating foraging group size: spider monkey food calls at fruiting trees. Anim Behav 39: 891–896
Elgar MA (1986) House sparrows establish foraging flocks by giving chirrup calls if the resource is divisible. Anim Behav 34: 169–174
Greene E (1987) Individuals in an osprey colony discriminate between high and low quality information. Nature (Loud) 329: 239–241
Gwinner E (1964) Untersuchungen über das Ausdrucks- und Sozialverhalten des Kolkraben (Corvus corax corax L.). Z Tierpsycho1 21: 657–748
Heinrich B (1988) Winter foraging at carcasses by three sympatric corvids, with emphasis on recruitment by the raven, Corvus corax. Behav Ecol Sociobiol 23: 141–156
Heinrich B (1989) Ravens in winter. Summit Books of Simon & Schuster, New York
Heinrich B, Bartholomew GA (1978) Roles of endothermy and size in inter- and intraspecific composition for elephant dung in an African dung beetle, Scarabaeus laevistriatus. Physiol Zool 52: 484–494
König C (1983) Interspecific and intraspecific competition for food among old world vultures. In: Wilbur SR, Jackson JA (eds) Vulture biology and management. University of California Press Berkeley, pp 153–171
Komers PE, Dhindsa MS (1989) Influence of dominance and age on mate choice in black-billed magpies: an experimental study. Anim Behav 37: 645–655
Krebs JR (1974) Colonial nesting and social feeding as strategies for exploiting food resources in the great blue heron (Ardea herodios). Behaviour 51: 99–134
Rabenold PP (1987a) Recruitment to food in black vultures: evidence for following from communal roosts. Anim Behav 35: 1775–1785
Rabenold PP (1987b) Roost attendance and aggression in black vultures. The Auk 104: 647–653
Stiehl RB (1978) Aspects of the ecology of the common raven in Harney Basin, Oregon. Ph D thesis. Portland State University, Portland
Waltz EC (1983) On tolerating followers in information-centers, with comments on testing the adaptive significance of coloniality. Colonial Waterbirds 6: 31–36
Ward P, Zahavi A (1973) The importance of certain assemblages of birds as “information centers” for food finding. Ibis 115: 517–534
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Heinrich, B., Marzluff, J.M. Do common ravens yell because they want to attract others?. Behav Ecol Sociobiol 28, 13–21 (1991). https://doi.org/10.1007/BF00172134
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DOI: https://doi.org/10.1007/BF00172134