A Moment of Science

Basking Birds

Over one hundred and seventy different species of bird have been observed sun-bathing.

Sunbathing crow in grass

Photo: laurencea (flickr)

A crow sunbathing in Hyde Park in London

You probably stopped in your tracks if you ever saw it happen: 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. After a few moments the bird hops up again and goes about its business. What’s happening here? Sun-bathing birds?

In fact, sun-bathing may be exactly what this is. To date over one hundred and seventy different species of bird have been observed sun-bathing. Why they do this, however, is a thorny question.

Some species of bird, such as the cormorant, are underwater divers. In order for them to be able to swim and grab fish they produce less feather-oil than other birds. Lower oil levels mean less buoyancy — thus easier diving — but it also means their feathers get soaked and stay that way. Diving birds may sunbathe as the fastest way to dry off.

Then what about something as dissimilar as a roadrunner? These desert birds have been observed sunbathing during the early morning hours, when ambient temperatures are down at the freezing point. The roadrunner will tip its feathers up to expose its black skin and thus absorb as much radiant energy from the sunlight as possible. It may sunbathe on and off to help it maintain a steady temperature in an environment of extremes.

So there may be many reasons for sun-bathing. Indeed, the theory that birds evolved from earlier reptilian life forms gains credence from this seemingly widespread habit; the basking of lizards may have developed over millennia into the numerous and multi-purposed baskings of birds.

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