Elevation and body size drive convergent variation in thermo‐insulative feather structure of Himalayan birds

Globally, high elevation habitats have been independently colonized by taxa separated millions of years evolution. Mountains thus represent excellent systems to study how distantly related species adapt the same environmental challenges. Cold temperatures influence elevational distribution birds along montane gradients. Yet eco-physiological adaptations that may explain this pattern, such as variation in insulative feather structure across and low has not quantified. We used a comparative approach understand if elevation, evolutionary history body size drive thermo-insulative traits 1715 specimens 249 Himalayan passerines. Controlling for phylogenetic relationships between species, we found proportion feather's plumulaceous (downy) section increased with elevation. Body also had predictable effect on variables small having relatively longer feathers more plumage than large birds. show an increase downy at colder is evolutionarily widespread response temperate tropical taxa, overall, smaller-bodied tend feathers. Our results reveal convergent patterns cold