A Place for All
Countercurrent heat exchange: Intricate networks of blood vessels act as countercurrent heat exchangers to heat blood as it returns from the foot to the body. This steep temperature gradient (yellow arrows) reduces heat loss and saves a tremendous amount of energy.
Just the other day while working at Placid Lake State Park, I observed a group of ducks gathered around a large space of open, ice-free water. Some were swimming and foraging in the shallow bottom gravel and mud, while others were situated near the edge of the ice mere inches from the cold open water. Of those birds on the ice, some were standing squarely on both feet while others were laying down; but there were three ducks who stood defiantly in the cold on one leg. One of those three even had its head twisted back and tucked into its plumage making it look like a one-legged, headless duck!...
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