How do they know?

I always used to wonder why our chickens would spread their wings, flop over and expose what little skin they could to the rays of the sun, summer as well as winter, often for surprisingly lengthy periods of time. They were especially keen on doing this after several cloudy days in a row. It couldn’t be that they wanted to get warm, since they live inside perfectly modulated duvets. It struck me only recently that they must be doing this to maximise vitamin D production. Since their instincts are clearly superior to mine, maybe I should draw up a chair, strip off and join them.

Here they are, hard at it, today:

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