title: Commonness and ecology, but not bigger brains, predict urban living in birds.
abstract: BACKGROUND
  Several life history and ecological variables have been reported to affect the likelihood of species becoming urbanized. Recently, studies have also focused on the role of brain size in explaining ability to adapt to urban environments. In contrast, however, little is known about the effect of colonization pressure from surrounding areas, which may confound conclusions about what makes a species urban. We recorded presence/absence data for birds in 93 urban sites in Oslo (Norway) and compared these with species lists generated from 137 forest and 51 farmland sites surrounding Oslo which may represent source populations for colonization.
  
  
  RESULTS
  We found that the frequency (proportion of sites where present) of a species within the city was strongly and positively associated with its frequency in sites surrounding the city, as were both species breeding habitat and nest site location. In contrast, there were generally no significant effects of relative brain mass or migration on urban occupancy. Furthermore, analyses of previously published data showed that urban density of birds in six other European cities was also positively and significantly associated with density in areas outside cities, whereas relative brain mass showed no such relationship.
  
  
  CONCLUSIONS
  These results suggest that urban bird communities are primarily determined by how frequently species occurred in the surrounding landscapes and by features of ecology (i.e. breeding habitat and nest site location), whereas species' relative brain mass had no significant effects.
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Oslo, Norway. svein.dale@nmbu.no.
authors.forename: Svein
authors.initials: S
authors.lastname: Dale
authors.affiliation: Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, NO-0318, Oslo, Norway. j.t.lifjeld@nhm.uio.no.
authors.forename: Jan T
authors.initials: JT
authors.lastname: Lifjeld
authors.affiliation: Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, NO-0318, Oslo, Norway. melissah.rowe@nhm.uio.no.
authors.forename: Melissah
authors.initials: M
authors.lastname: Rowe
mesh_terms: D000222:Adaptation, Physiological; D000383:Agriculture; D000818:Animals; D001717:Birds / Q000033:anatomy & histology*; D001921:Brain / Q000033:anatomy & histology*; D002947:Cities; D017753:Ecosystem; D065928:Forests; D008954:Models, Biological; D009664:Norway; D009929:Organ Size; D010802:Phylogeny; D011156:Population Density; D011157:Population Dynamics; D012044:Regression Analysis; D014507:Urbanization