Bird Jacket: Mountain chiffchaff

A variety of songbirds, or passerines, in the wild, representing several of the species studied by the research team.

Sahas Barve, a Peter Buck Fellow at the Smithsonian’s National Museum of Natural History, led a new study to examine feathers across 249 species of Himalayan songbirds, finding that birds living at higher elevations have more of the fluffy down—the type of feathers humans stuff their jackets with—than birds from lower elevations. Published on Feb. 15 in the journal Ecography, the study also finds that smaller-bodied birds, which lose heat faster than larger birds, tend to have longer feathers in proportion to their body size and thus a thicker layer of insulation.