Data from: Commonness and ecology, but not bigger brains, predict urban living in birds

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.