How Do Birds Survive Winter

Photo Group
American Goldfinch
Photo by: 
Mary Nemecek

It is easy to understand why people rush out and buy bird seed when it snows. How can something so small and fragile possibly survive such brutally cold conditions? As with most wild animals, many of their survival techniques are the same as ours.

First and foremost we have to remember that birds, like humans and other mammals, are homoeothermic (warm blooded). This means that as long as birds can find a suitable food source, their bodies can convert that food into energy (i.e. body heat).

You’ve probably heard me talk about birds that winter here from up north. Cold temperatures are survivable by most birds, it is the covering of the food source that is the main problem. Ground feeders and waterfowl know that their food sources are going to be covered up quickly but arboreal (tree dwelling) species like evening grosbeaks and crossbills can ride out the same “cold” conditions that juncos and snow geese abandon.

How do these tiny, fragile creatures endure temperatures like -20 degrees? Like us, they often try to find places that are well protected from wind and “cold air”. Evergreen trees provide very important cover as do artificial or natural cavities. Within these day or night roosting areas you can often find several birds. Bluebirds, wrens and others will huddle, bunch or even stack on top of each other to keep warm.

While certain species of birds do add more feathers in winter, all birds can fluff up. By fluffing up and creating air space between feathers as well as feathers and skin, it is like putting on an jacket. This is why you will hear me talk about the importance of a heated bird bath. Water is essential to keeping feathers healthy and healthy feathers are essential to keeping warm.

When conditions get even worse, shivering can help. Shivering is our (and a bird’s) body’s way of generating a little extra heat.

Perhaps the most amazing adaptation bird have for dealing with the cold is their ability to lower their body temperatures a few degrees. Used as a way to conserve oxygen in the blood stream, it is known as hypothermia and is used primarily while sleeping.

Hummingbirds and a few other species can drop their body temperatures drastically. This condition is known as torpor. For species, like hummingbirds, with extremely high metabolic rates, this is the only way they do not “starve to death” while sleeping. Hypothermia and Torpor do not come without hazards. A bird in torpor can’t take off and fly if danger approaches, in fact, it can take a bird an hour or so to regain full muscle control.

What does this winter have in store for us? As all Missourian know, there really is no way to know for sure. Don’t forget that the food and water you are providing is important to birds, especially during the brutal stretches.

By Mark McKellar

WINTER 2003