Birds hold a layer of soft, fluffy feathers that regulate body temperature

Feathers are an elegant, intricate evolutionary innovation that allows birds to fly, but in addition to the stiff, aerodynamic feathers used for flight, birds also retain a layer of soft, fluffy feathers between their bodies and end feathers to regulate body temperature.

Using Smithsonian’s collection of 625,000 bird specimens, Sahas Barve, a collaborator of Peter Buck of the Smithsonian’s National Museum of Natural History, conducted new research to examine feathers on 249 species of Himalayan songbirds, finding that birds living on higher elevations have more than fluffy down – the kind of feathers that people use to fill their jackets – than birds from lower elevations.

Published February 15 in the journal Ecography, the study also found that birds with smaller bodies, which lose heat faster than larger birds, usually have longer feathers in proportion to body size and thus a thicker layer of insulation.

Finding such a clear pattern in so many species underscores how important feathers are for a bird’s ability to adapt to its environment and suggests that addition may be a strategy common to all songbirds or pigeons, as known to researchers. Furthermore, the discovery that birds from colder environments tend to have more fluff may one day help researchers predict which birds are most susceptible to climate change just by studying their feathers.

The Himalayas record some of the fastest warming rates on Earth. At the same time, climate change is leading to an increase in the frequency and intensity of extremely cold events such as snowstorms. The ability to accurately predict the temperatures a bird can withstand could provide us with a new prediction tool so that certain species can respond to climate change. “

Sahas Barve, Peter Buck Fellow, National Museum of Natural History, Smithsonian

The research was inspired by a tiny bird called the Golden Reef during a cold morning of field work in the Sho-kharkh forest in the Himalayas. Colors wondered how this bird, which weighs about the same as a teaspoon of sugar, could fly around the treetops in the icy air that had already numb his fingers. Pushing his hands back into the pockets of his thick down jacket, Barve was asked, “Do Himalayan birds wear down jackets?”

To answer that question, Barve and his co-authors used a microscope to record the pectoral fins of 1,715 specimens from the Smithsonian collection representing 249 species from the cold high mountains of the Himalayas.

Then Barve and his co-authors used these super-detailed photographs to determine exactly how fluffy a part of each feather was in relation to the total length. The team managed this by looking at the fluffy fluffy part of each feather near its base compared to the measured ends of the feathers of most birds.

After recording in detail the relative lengths of all those fluffy parts, Colors analyzed the results and found that the smallest birds and birds from the highest elevations, where temperatures are coldest, have the highest proportion of feathers on the body feathers.

The analysis showed that birds of high elevations had up to 25% more feathers, and the smallest bird had feathers three times longer than the largest birds, in proportion to their body size.

Past research has suggested that birds from colder habitats had additional fluffy isolation, but Barve said this is the first study to analyze this pattern for such a large number of species in a cold environment and over 15,000 feet above sea level.

“Seeing this correlation in so many species, our findings are more general and allow us to say that these results suggest that all birds of the breed can show this pattern,” Barve said. “And we could never look at so many different species and come up with this more general evolutionary pattern without the Smithsonian collections.”

Carla Dove, who runs the museum’s pen identification laboratory and contributed to the study, said she is excited to use the Smithsonian’s collections in a new way along with Barve. “

Sahas looked at more than 1,700 copies. Having them all in one place in downtown Washington, DC, as opposed to having to go to the Himalayas and study these birds in the wild, is obviously a big difference. It allowed him to quickly collect data before COVID locks hit the world and then remotely processed the analysis. “

Barve said that he is following this study with experiments that investigate how much isolation birds get from their feathers, and then they will connect that with the structure and the share of feathers. One day, Colors aims to develop a model that will allow scientists to look at the structure of feathers and predict how much isolation it gives birds – an ability that could help researchers identify species vulnerable to climate change.

Dove said the potential of using these results to eventually understand how some birds can cope with climate change underscores the importance of museum collections.

“We have more than 620,000 specimens of birds collected over the past 200 years, waiting for studies like this. We don’t know what our samples will be used for; so we need to maintain and constantly improve them. These specimens from the past can be used to predict the future.” support for this research was provided by the Smithsonian.