2 =0.34, P=0.006) and winter (R 2 =0.40, P=0.037) birds. Data were also subjected to a comparative analyses with phylogenetically independent contrasts to remove potential confounding effects of phylogeny, and results were similar to the non-phylogenetic analyses, with significant negative correlations in both summer (R 2 =0.47, P<0.001) and winter (R 2 =0.40, P=0.049). Thus, birds with high M sum tended to show reduced T CL (i.e. high cold tolerance), suggesting that cold tolerance and summit metabolism are phenotypically linked in small birds.

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