title: Living in stable social groups is associated with reduced brain size in woodpeckers (Picidae).
abstract: Group size predicts brain size in primates and some other mammal groups, but no such relationship has been found in birds. Instead, stable pair-bonding and bi-parental care have been identified as correlates of larger brains in birds. We investigated the relationship between brain size and social system within the familyPicidae, using phylogenetically controlled regression analysis. We found no specific effect of duration or strength of pair-bonds, but brain sizes were systematically smaller in species living in long-lasting social groups of larger sizes. Group-living may only present a cognitive challenge in groups in which members have individually competitive relationships; we therefore propose that groups functioning for cooperative benefit may allow disinvestment in expensive brain tissue.
authors.affiliation: School of Psychology, University of St Andrews, St Andrews, Fife KY16 9JP, UK.
authors.forename: Natalia
authors.initials: N
authors.lastname: Fedorova
authors.affiliation: School of Biology, University of St Andrews, St Andrews, Fife KY16 9ST, UK caraevans1@googlemail.com.
authors.forename: Cara L
authors.identifier: 0000-0002-7116-3646
authors.initials: CL
authors.lastname: Evans
authors.affiliation: School of Psychology, University of St Andrews, St Andrews, Fife KY16 9JP, UK rwb@st-andrews.ac.uk.
authors.forename: Richard W
authors.identifier: 0000-0001-9862-9373
authors.initials: RW
authors.lastname: Byrne
mesh_terms: D000818:Animals; D001717:Birds / Q000033:anatomy & histology* / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology*; D009929:Organ Size; D010152:Pair Bond; D010802:Phylogeny; D012919:Social Behavior
keywords: brain evolution; group size; social complexity; social intelligence theory