If you stood outside in any eastern Canadian city in January or February without a stitch of clothing on, you'd likely turn into a Popsicle in fairly short order. Instead, you find yourself donning a warm winter coat, thermal mitts and wool-lined boots. But what about the birds? Not all of them head to warmer climes in winter, so how do they cope in a frozen landscape during our long winter months?
Actually, birds have an amazing number of behavioral and physiological adaptations for surviving the coldest of conditions. It has a lot to do with their most unique feature - feathers. If you're looking for natural lightweight insulation, you couldn't find better than bird feather coats. Just like we throw on extra clothing to combat winter cold, some birds enhance their insulation from feathers by molting into fresh, thick plumage. Some sparrows that spend their winters in chilly areas actually increase their plumage weight by as much as seventy percent from summer to winter!
Ever watch a bird on a really cold day fluff out all its feathers to look like a little butterball? The bird is simply adjusting its feathers to create warm air pockets to increase the insulation value of its plumage. It's the same principle as when you buy a winter coat -- you want it loose so that your body heats the trapped air to provide an extra layer of insulation.
And what about those ducks and geese that spend hours bobbing around in water barely above freezing temperature!? They do have waterproof plumage, but what keeps their legs and feet from becoming frost-bitten and eventually gangrenous? First, they reduce the circulation in their feet to a mere trickle in a network of blood capillaries. Just enough to keep the tissue cells alive. Second, through a special countercurrent heat exchange system, the arterial blood flowing to the feet heats up the cool venous blood returning to the body. All of this serves to keeps the heat from being lost to the outside.
And here's another trick we humans can't do. At night-time, especially in extremely cold weather, birds can lower their body temperature a few degrees to conserve energy. You see, when a bird becomes cold, it tenses its breast muscles and begins to shiver to generate body heat. Unlike us, they do this in an almost imperceptible manner.
There are behavioral adjustments too. In really cold wintry weather, birds favour sheltered or wind-protected areas in both feeding and roosting locations and waterfowl often tuck their heads into their “armpits”. Some species like grouse, ptarmigan and even snow buntings plunge into soft snow and use their body heat to warm up their "cave. On nights when temperatures are exceptionally frigid, some small birds will pack themselves into tree cavities. On one occasion, up to 50 titmice were found huddled in a ball-like mass in a cavity.
So don't worry about the birds in winter.
Nature has provided them with an array of adaptations. After all, if they couldn't handle it, they wouldn't stay, right?!