Birds need to care for their feathers. They are important for such functions as flight, attracting mates, camouflage, regulating body temperature, and keeping dry.
On warm, sunny days out at the arboretum I will occasionally catch a Steller’s Jay or an American Robin performing an interesting behavior called sunning. This maintenance behavior isn’t completely understood but seems to be largely associated with removing parasites, such as lice, living on their skin and feathers. Studies have shown that exposing the feathers to direct sunlight can allow them to heat up enough to kill some of the lice. In addition, lice might move to escape the heat possibly making it easier to clear them away during preening, which often follows a session of basking in the sun.
While scientists continue to unravel this mystery of sunning, one thing for sure is that we will all continue to marvel at the beautiful diversity of the colors and patterns of bird feathers.
Nature is an inexhaustible source of wonder. I look forward to seeing you out there.
Resources
Hot, Bothered, and Parasite-Free: Why Birds Sun Themselves | Audubon. 27 Feb. 2020, https://www.audubon.org/news/hot-bothered-and-parasite-free-why-birds-sun-themselves.
Sibley, David. What It’s Like to Be a Bird: From Flying to Nesting, Eating to Singing -- What Birds Are Doing, and Why. Alfred A. Knopf, 2020.