Evol Ecol Res 6: 833-842 (2004)     Full PDF if your library subscribes.

Is there a relationship between forebrain size and group size in birds?

Guy Beauchamp1* and Esteban Fernández-Juricic2

1Faculty of Veterinary Medicine, University of Montréal, PO Box 5000, St-Hyacinthe, Québec J2S 7C6, Canada and  2Department of Biological Sciences, California State University Long Beach, Peterson Hall 1-109, 1250 Bellflower Boulevard, Long Beach, CA 90840, USA

Author to whom all correspondence should be addressed.
e-mail: guy.beauchamp@umontreal.ca


The social complexity hypothesis of brain size evolution posits that demands from group living can favour an enlargement in brain size to allow individuals to process the greater amount of social information generated by group members more efficiently. We tested the hypothesis in birds using estimates of forebrain size from three different data sets. Phylogenetically corrected analyses indicated a lack of relationship between forebrain size and two indices of social complexity, namely mean or maximum flock size in the non-breeding season. Forebrain size was also unrelated to the propensity to flock. In contrast to primates, where the social complexity hypothesis was first proposed, it is conceivable that in birds social demands in the non-breeding season may be insufficient to drive brain size evolution. Future research could focus on the possibility that more specific areas of the avian brain are associated with group size and could be extended to cooperative breeding species that forage in more complex groups over much of the year.

Keywords: birds, flock size, forebrain size, phylogenetic analysis, social complexity hypothesis.

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