My feet get uncomfortably cold very
easily. If I spend even a short time outside in freezing conditions, even while
wearing insulated boots, my toes go numb and my feet start to ache. I think
it’s a genetic thing. My parents used to complain about their cold feet while
standing around various ice rinks while I was playing hockey as a kid. And now
I have the same problem.
Yet ducks, geese and a number of
other birds are apparently unbothered by the cold as they stand on ice-covered
ponds in their bare feet. What do they have that people don’t have? It’s one of
the most common questions I get about birds at this time of year. Why don’t
they rock back and forth, stomp their feet, or use any number of other
strategies that humans employ to keep their feet warm?
The answer, according to University
of Rhode Island ecologist Scott McWilliams – my go-to guy for all bird
physiology questions – has a lot to do with blood circulation. The birds have
Cartoon by David Chatowsky |
“It’s a common solution to the
problem of keeping your body core warm and not having to expend a ton more
energy trying to keep your entire body warm, including your extremities,”
McWilliams said.
Ducks also have downy, waterproof
feathers and a thick layer of body fat to keep them warm in freezing
conditions. If the weather gets extremely cold and the birds feel the chill,
they have several additional options. They can stand around on one foot while
tucking the other foot in their feathers to keep it warm, or they can fluff up
their feathers to trap more of their body heat, which provides an insulating
blanket around their bodies.
Like almost all other birds that
live in a cold climate for at least part of the year, ducks can also slow their
metabolism to conserve energy. For tiny birds like kinglets, this strategy can
save as much as 20 percent of their daily energy budget.
Birds also have something called
brown fat, which is designed to produce heat through a biochemical process,
much like humans do by shivering. And then there’s McWilliams’ favorite
strategy – huddling. Many small birds will gather together in tight groups
during chilly nights to share their body heat.
While I understand how these
physiological adaptations enable birds to survive most winters unscathed, it
still amazes me that the adaptations do the trick when temperatures remain well
below freezing for weeks at a time, like that two week stretch around New Years. It’s especially impressive that
tiny birds like chickadees make it through such cold snaps.
Still, if birds can spend the whole
winter outside, why can’t I last for more than an hour or two? Maybe I need to
grow some downy feathers. Or brown fat.
This article first appeared in the Independent on January 18, 2018.
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