Warm Bodies

Colorful barelegged creatures with the gifts of flight and song are surely a great marvel of the winter landscape.

Red-winged Blackbird

Their concerts are not cancelled by irregular weather. To be sure of its melodies Nature must keep songbirds warm.

Tree Swallows during spring snowstorm

Photo courtesy of Keith Williams/Creative Commons

Huddling birds can share their warmth, reduce exposure to cold air, and shield each other from wind.

Brant

The hard work of flight generates more than enough heat for a comfortable body temperature while a bird is active.

Robin

At rest they are likely to fluff their feathers and wrap themselves in their wings as advantageously as possible.

Snowy Owl

Snowy Owls even have feathered feet.

Common Eider

Eiders, one of our winter coastal ducks, have some of the most effective insulation of any bird. Their perfectly interlocked outer feathers form a 'barrel'  to trap pockets of air around their bodies even when diving. The birds waterproof this guard layer by using their bills to coat it with oil from a preening gland near the base of their tails. Eiders are also the source of down feathers utilized in superior winter clothing and bed comforters.

Varieties of feathers

Illustration from The Birdwatcher's Companion by Chris Leahy

Intricate combinations of feather structures beneath the outer layer keep the bird warm as well as streamlined for flight.

Mourning Dove

A few species of birds like egrets, herons and mourning doves grow special feathers that disintegrate into a powder they use to waterproof their feathers.

Black-capped Chickadee

Chickadees weighing less than half an ounce can maintain a daytime body temperature of 100 degrees Fahrenheit by having great insulation, being very active and remembering where they store their food. They eat more than a third of their weight every day. Compared to many other birds, chickadees have a large hippocampus - the part of the brain that’s responsible for spatial memory. In the fall, this part of their brain gets even bigger!

These small creatures can't put on too much bulk for aerodynamic reasons. Instead, they are experts at shivering. Birds activate opposing muscle groups to create contractions without all the familiar trembling that mammals use to generate heat. At night, tucked into a tree cavity, they might reduce their body temperature as much as 22 degrees from their daytime level in a process called regulated hypothermia.

Chickadee foot temperature is regulated near the freezing point and may stay cold most of the time all winter, even as core body temperature stays high. Of course, a bird’s comfort level for foot temperature is likely very different from ours. They would not feel uncomfortable until the point when damage occurs from freezing, if ice crystals were to form.

Online information on Chickadees
1. U. S. Fish & Wildlife Service Newsroom, "How do birds keep warm in the winter?"
2. Audubon.org, "How Do Birds Cope with Cold in Winter?"
3. Cornell Lab All About Birds, "How Do Birds Survive the Winter?"