This is Bird Note. In the depths of winter, when sub-zero temperatures last for months,

and most lakes and ponds are frozen over, how do birds stay hydrated? Water derived from food

alone is not enough, especially since juicy insects are in short supply this time of the year. Instead of

flying long distances and losing precious energy in search of liquid water, birds imbibe the

frozen water that's all around them, while cedar wax wings sally to catch snowflakes from midair.

Plenty of other birds, including the red-breasted nut hatch, white-tailed tarmigan,

pilliated woodpecker, and Bohemian Waxwing, scoop up fresh powdery snow from the ground, trees, or rooftops.

Black-capped chickadees drink the water dripping from icicles.

The northern flicker hammers at the icy top layer of snow and eats the tiny shards of ice

that chip off. Eating all that ice comes at a cost.

It takes energy to convert ice and snow to water

and warm it up to the body temperature of a bird.

But it may be worth the calories for, say, a red-breasted nut hatch

when the alternative is to break off from the flock

in search of liquid water, leaving it exposed to predators, such as hawks.

For Bird Note, I'm Michael Stein.