On this very cold morning everyone’s working hard to stay warm but some have an easier time than others. Who loses heat faster, the chickadee or the raven?
Just like us, birds burn calories no matter what they’re doing. However, birds have higher metabolic rates than mammals and require more calories for everything they do. Any activity, from sleeping on an empty stomach to a burst of rapid flight, burns more energy than in vertebrates of a similar size.
Small birds have higher metabolic rates than large ones because of the relationship of surface to volume. Heat dissipates from the surface of an object so the more surface there is, the greater the heat loss. So, yes, the chickadee loses heat faster than the raven. That’s why northern animals are often larger-bodied than those who live in warmer climates. Even among chickadees the black-caps in Maine are noticeably larger than the chickadees in Pittsburgh.
To stay warm the chickadees will look fatter today because they’ll fluff their feathers to raise the loft of their down coats. They’ll also cover their legs to reduce heat loss and they will eat — a lot! — to replace the calories they’re rapidly burning.
“Eat like a bird?” Today all birds, and especially the little ones, are chowing down to stay alive.