Researcher
Categories
2013Abstract
Our original paper [1] included two Bayesian analyses [2] of the association between
brain size and the probability of a passerine species of bird breeding in the city
centre—at the level of families and at the level of individual species—with both analyses
suggesting the same pattern. It has since been brought to our attention that in
one of the analyses at the level of individual species, the residual variance was not
fixed to 1 resulting in overestimation of the variance. We re-ran the analysis using
fixed residual variance and the results support the original conclusion that relative
brain size is associated with breedingin the city centre (ln brain size: posterior mean,
324.53, 95% credibility interval, 52.61–601.35; ln body size: posterior mean,
2276.22, 95% credibility interval, 2490.60 to 270.32). Furthermore, we applied a
complimentary approach using logistic regression to test whether brain size predicts
breeding in the city centre (yes/no) without accounting for phylogeny. This
analysis also resulted in a significant positive association between brain size and
breeding in city centres (likelihood ratio tests: ln brain size: d.f. ¼ 1, x2 ¼ 11.08,
p ¼ 0.0009; ln body size: d.f. ¼ 1, x2 ¼ 11.26, p ¼ 0.0008). Thus, our results are
confirmed by both phylogenetic and non-phylogenetic analyses.