It's getting to that time of the year when fingers and toes get cold, and it's enough to make a grown person cry to see birds nonchalantly walking about in their bare feet. It's even worse to see ducks paddling happily between patches of ice or even resting on an icy pond bank. Ah, we know that envy is a sin, but really!
So how do they do it? Simple. They use countercurrent heat exchangers.
Oh, you're not familiar with those? Actually, it's pretty neat. The arteries
carrying hot blood from the body toward the legs are wrapped around by veins carrying
cold blood from the legs and feet. The warmth from the arterial blood is passed over to
the venous blood, with the result that blood going to the legs is pre-cooled and the
blood returning to the body pre-warmed. With muscles bunched up next to the body and
few nerve ending for coldness down below, a bird on ice is as happy as if it had good
sense. Nice system; we could almost say, really cool! 
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.