How do birds stay warm in winter?

You’re at the park with a thick winter coat, hat, gloves, scarf, and warm boots, and you’re still numb and shivering from the cold. Then you notice a blackbird hopping from branch to branch. Nearby, ducks swim peacefully in the pond and waddle on the ice.

How do birds survive such freezing conditions?

A natural thermal base layer

Birds have a big advantage over us: feathers.

In winter, birds have more feathers. “Their feather density increases between 35 and 70 percent during the colder months,” says Ava Michelangelo, teaching naturalist at the Connecticut Audubon Society.

“Just as our attire changes from T-shirts and shorts in summer to jackets and long pants in winter, these birds undergo a similar change.”

Birds have different types of feathers, and one type is especially important in cold weather: down. These feathers are very fluffy and grow close to the skin, essentially acting as a thermal base layer. “Of the many types of feathers that birds have, down is excellent for retaining body heat,” says Anna Pidgeon, professor of forest and wildlife ecology at the University of Wisconsin-Madison.

(Unfortunately, this has also led to down feathers being used to stuff jackets, duvets and other items, although ethical brands now use synthetic insulation that mimics down.)

Why do birds swell in winter

You may also notice that birds appear very round and bloated in cold weather. “What they do is trap air between their feathers, which is then warmed by their body,” explains Michelangelo.

Birds also reduce heat loss by covering parts of their bodies without feathers, Pidgeon says. For example, they may tuck their beaks into the feathers on their backs or under their wings and crouch to cover their bare legs and feet.

They can also stand on one leg, with the other leg tucked between their chest feathers. This reduces the surface area of ​​bare skin exposed to the cold by half.

Sheltered from the cold

When it’s extremely cold and windy, birds seek shelter, just like us humans.

Pidgeon explains that some birds, like larks and snow buntings, hide behind small bumps in the ground to block the wind. Others, like the rock ptarmigan and black grouse, burrow into the snow, using it as insulation.

“Some birds are lucky enough to have a suitable cavity in their wintering area, for example in a dead tree or with a decaying branch,” says Pidgeon. Woodpeckers often sleep alone in these shelters, but smaller birds, such as chickadees, bluebirds and chickadees, sometimes huddle together in cavities, “taking advantage of each other’s body heat.”

Designed for the cold

While many birds avoid winter altogether by migrating, those that stay behind are often specially equipped for the cold.

“The birds we see year-round in Connecticut, like the beloved black-capped chickadee, are species that do very well here in winter,” says Michelangelo.

“They constantly shake to generate heat when they search for high-fat foods, like seeds.” Shivering works the same way in birds as it does in humans: moving muscles burns energy, and that energy turns into heat.

Ducks, seagulls and other waterfowl also have an amazing trick. “On days when the salt marsh is frozen, you will still find these birds resting on the frozen ice,” explains Michelangelo.

Waterfowl also have very few pain receptors in their feet, so they don’t feel the cold like a human would if standing barefoot on the ice. Additionally, they reduce heat loss through a process called counter-current heat exchange. Heat from warm blood flowing down to the feet is transferred to colder blood returning to the body before reaching the core. This way, the bird’s core temperature does not drop, but its legs still receive enough oxygen to function.

Research has also shown that gulls can limit the amount of blood going to their feet, Pidgeon says. This reduces the amount of body heat lost to the icy surface or water.

Fuel for heat

Just like people stock up before a snowstorm, many birds store their food in advance. During warmer months, they hide seeds and insects in bark crevices and under the edges of lichens so they can eat later when food is harder to find, Pidgeon says.

If food is particularly scarce, some birds have another strategy: daily torpor. This is a short period where they lower their body temperature, heart rate, and breathing to conserve energy. This is not the same as hibernation and usually lasts less than 24 hours. In hummingbirds, torpor can reduce energy consumption by up to 95%!

Chickadees also have a dietary superpower that helps them survive the cold months. “Their hippocampus, the part of their brain that stores memories, is larger in winter,” explains Michelangelo. “It helps them remember where they hid their food.” »

A single chickadee can store up to a thousand seeds per day, or 80,000 per season. (In contrast, a single squirrel only buries up to 3,000 nuts per season.)

So yes, winter may be harsh, but the birds are ready for it.

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