The feathers of 250 species of Himalayan songbirds have revealed that birds living at higher elevations have more of the fluffy down than birds from lower elevations. This provides them with efficient protection from extreme cold.
The study also found 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.
The Smithsonian’s National Museum of Natural History has a collection of 625,000 bird specimens. The scientists used a microscope to take photos of the chest feathers of 1,715 specimens from the Smithsonian’s collections representing 249 species from the cold, high-altitude Himalayan Mountains.
Past research suggested that birds from colder habitats sported added downy insulation. But this is the first study to analyse this pattern for such a large number of species in cold environments and across 15,000 feet of elevation.
The study aims to develop a model that will allow scientists to look at the structure of a feather and predict how much insulation it gives the bird–a capability that could help researchers identify species vulnerable to climate change.