West River Eagle

How birds beat the cold



It was a dark and stormy night. 

Actually, it has been a warm fall down here in Vermillion. This time two years ago, we had several inches of snow on the ground, but this year, we’ve only had a dusting and the temperatures over Thanksgiving weekend averaged in the 50s.

Still, winter is coming, and it’s not an easy season for birds.

The most obvious way birds beat the cold is by not having to deal with it at all; about 1/3 of the bird species in North America are seasonal migrants. Those hummingbirds who fought over my feeders all summer are safely in Mexico by now. 

Birds who stick around in cold climates have developed a number of survival strategies. Some species, like swallows, roost together so that their combined body heat keeps them warm, while others, like nuthatches or woodpeckers, nest in tree cavities to keep out of the wind. 

Feathers help provide insulation, and they can thicken as winter arrives. According to Birds and Blooms Magazine, Dark-eyed Juncos have a 30% heavier coat in winter than in summer. Puffing up the feathers traps air and helps keep the bird warm, and oil from a gland near the tail that birds spread when preening helps keep their outer feathers waterproof. 

Some birds, like Black-Capped Chickadees can increase heat production by shivering and thus maintain their body temperature at about 100 degrees Fahrenheit. According to the U.S. Fish and Wildlife Service, the hippocampus, the part of the brain that controls memory, gets bigger in chickadees in the winter so they can find their caches of food. This is a good thing, as they have to eat about 1/3 of their body weight a day.

We often see ducks and geese standing on ice or swimming in near-freezing waters. While we would get frostbite, birds generally don’t. Their feet make use of something called a countercurrent heat exchange system.

Cornell Lab of Ornithology explains what this means, “The blood vessels going to and from the feet are very close together, so blood flowing back to the body is warmed by blood flowing to the feet.” This means that heat isn’t lost through the feet and the bird doesn’t have to work as hard to keep its body temperature up. It helps, too, that their feet don’t have a lot of muscle or nerve endings. Most waterfowl can comfortably stand on one foot at a time, tucking the other up inside their feathers and further reducing heat loss. 

All of these strategies cost energy, and they happen in the winter when days, and therefore foraging hours, are shorter and food is scarcer. We can help birds survive the cold by providing high-energy food appropriate to the birds in our areas (Project Feederwatch at feederwatch.org has lots of good advice). Roosting boxes can give birds a place to shelter on cold (and stormy) nights. A heated birdbath can provide them with fresh water when other sources are frozen. And since birds tend to flock to feeders in the winter, keeping feeders and birdbaths clean can help prevent the spread of disease. 

Winter in South Dakota is a great time to see birds, from waterfowl that collect on lakes to the owls that will soon begin “hooting season” to the small birds that flock to our feeders. I hope you enjoy the season. 

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