You see a large bird, such as a crow, spread out flat on the grass with its wings fully extended and its body pressed to the ground. It stops you in your tracks. Is the bird hurt? Is it sleeping?

After a few moments the bird hops up again and goes about its business. What's happening here? Do bird sunbathe?

In fact, sunbathing is exactly what this is. Over one hundred and seventy different species of bird have been observed sunbathing. Ornithologists think birds do these things to: drive parasites out of the birds' feathers and spread preen oil throughout their plumage.

Parasites and Preen Oil

Remember, feathers aren't just necessary tools for flying, they're also insulation. Preen oil, which is still being studied on a species by species basis, conditions and maintains the quality of the feathers. Some scientists think that in birds like the cormorant, preen oil also helps to waterproof their feathers.

Another reason why scientists think that birds sunbathe is to help rid their plumage of parasites. The sun's heat drives out the parasites that live in their plumage. Without cleaning and maintenance, some kinds of parasites will even start eating the birds' feathers.

One other reason why birds might sunbathe? Environment. Desert birds such as the roadrunner will sunbathe in the early morning hours, especially after cold desert nights.

The roadrunner will tip its feathers up to expose its black skin and thus absorb as much radiant energy from the sunlight as possible. This helps them to conserve heat for the cold nights ahead.

Read More

• Blem, C. R. & Blem, L. B. 1992. Some observations of sunbathing in swallows. Journal of Field Ornithology 63, 53-56.

• "Greater Roadrunner." The Cornell Lab of Ornithology. November 9, 2016.

• Naish, Darren. "Sunbathing Birds." Scientific American. August 1, 2011. Accessed November 9, 2016.

• "Sunbathing Birds." British Trust for Ornithology. Accessed November 9, 2016.