Birds in various climates and all around the world indulge in sunning. This can be anything from simply standing with their backs to the sun with their feathers rustled up to expose the skin below, to a full sunbathing posture with wings and tail feathers spread out to maximize the area open to the sun, like this Bald Eagle. Some birds such as pigeons will be on one side and raise a wing to the sun. Whatever the exact action, like 'smoke bathing' the causes, or benefits to the bird are a matter of supposition. Obviously, in many cases the birds get warmth from the sun which reduces the amount of metabolic energy they have to expend in order to maintain a constant body temperature of around 40 degrees C. However, some birds sunbathe in temperatures which are quite hot, in such circumstances sunbathing appears to leave them over-heated as they can be seen panting. Therefore, some scientists have theorized that the sun's warmth is important in helping dislodge feather parasites, or that the ultra-violet in sunlight helps turn some precursor molecule in the preening oil into vitamin D and that the bird's need this vitamin. It is known that these precursor molecules exist in preening oil and that ultra-violet light will stimulate the conversion into vitamin D. What is not known is how well this happens on the bird's body and how important the amount of vitamin D created would be to the bird. I have also seen other birds appearing to sunbathe but on closer inspection found it was an anthill they were sitting on I presume this behaviour was to make use of the insects own chemicals to kill off parasites..