From our partners at the Audubon Society:
Winter birds have a better chance of maintaining their territory year-round, and they avoid the hazards of migration. But in exchange they have to endure the cold.Like us, birds are warm blooded, which means their bodies maintain a constant temperature, often around 106 degrees Fahrenheit. To make enough heat, and maintain it, they’ve evolved many different strategies–some similar to our own.
Sparrows, for example, seek out shelter in dense foliage or cavities to avoid the elements. They also huddle, bunching together to share warmth, and try to minimize their total surface area by tucking in their head and feet and sticking up their feathers. Cardinals… puff up into the shape of a little round beach ball to minimize heat loss.
Big birds, like geese and grouse [grow] an extra set of insulating downy feathers.
You can see Bald Eagles and various winter warriors on the live cam from the Audubon bird sanctuary in Seal Island here!