For the Birds Radio Program: Canada Geese in Winter
Geese in Winter
Imagine sitting on a frozen lake with bare feet, naked as a jaybird, during the worst of a north country winter. For many Canada Geese, that’s business as usual.
Unless every area lake freezes or deep snow covers farm fields and open grass, at least a few geese winter here, eating waste grain, exposed weeds and grass, and aquatic plants. Some do migrate during frigid weather, but usually return when temperatures climb into the 20s or 30s again. With an overall warming trend, more and more geese are staying north the entire winter, and even when the mercury drops into the sub-zero range, they stick around close to open water. The baby geese from the previous summer stay with their parents, learning where to go and how to deal with bad conditions. If their parents had only been exposed to balmier winters, they will be figuring out how to deal with deep freezes at the same time their young are. But geese are clannish, sticking to their flocks which include many previous generations, so the oldest ones, who are more likely to have experienced a huge range of winter conditions, serve as leaders.
Advantages to remaining in the north are less competition for food than farther south, and fewer predators, especially for urban geese who don’t have to worry about wolves and bobcats. They also get a jump on the most favorable territories come spring. And as long as there is open water, they can be submerged in temperatures above 32 degrees—the water can be as much as 50 or 60 degrees warmer than the air during our coldest weather.
Why don’t they freeze? Geese wear thick down jackets—dense, insulating feathers that trap body heat beneath watertight outer plumage. During fierce storms, they face into the wind, so their streamlined feathers minimize the impact and don’t ruffle up, letting cold air into their warm insulation. Their big bare feet operate with tendons, not muscles, so their leg and foot tissues have little fluid to freeze, protecting them from frostbite. Birds also control blood flow to their feet, dramatically reducing heat loss. Their arteries and veins intertwine at the base of the legs so that cold blood flowing back into the body is heated by blood flowing down to the feet. To reduce heat loss even more, geese stand on one foot with the other tucked under belly feathers. Birds have a more efficient and water-conserving respiratory system—even on the coldest days you won’t see much frost around a goose’s nostrils.
As days grow longer and warmer, geese grow restless. Soon the 37-degree isotherm will reach us on more and more days. When the average day/night temperature reaches 37 or 38 degrees, the bulk of Canada Geese will be passing through. This tends to happen during the worst part of spring—when freezing rain and rain mixed with snow are standard conditions. Fortunately, those outer feathers that protect their downy underfeathers are waterproof.
To human eyes they may look uncomfortable, but for a goose, winter and early spring are just ducky.