Photo: Swan tucks in for a nap

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Our photo of the day is a lesson in energy conservation, bird-style.

I don't know about you, but when I can't sleep, a pillow over my head lulls me back into slumber. If I were a bird, I would be so happy to have a nice fluff of feathers to bury my head in.

But in fact, blocking out the world is not why birds sleep with their faces nuzzled into their feathers, like the mute swan is doing in this photo by davygenney. It's all about conserving energy! Just like how water birds stand on one leg to minimize heat loss, so do they tuck their bills into their feathers while sleeping, which works to keep things warm and cozy.

Would you like to see your nature photo featured as the TreeHugger photo of the day? Join TreeHugger’s Reader Photo Pool on Flickr and add your pictures to the group.

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