We were bird watching the other day in Wonderopolis when we spotted a cardinal and a vulture having a conversation at the local watering hole. We were too far away to hear them, but we could read their beaks through our binoculars:
Cardinal: Nope! Not yet. How about you, Larry?
Vulture: Not quite, but I have a plan. You headed south again this year?
Cardinal: You bet. Florida is sounding really good about now. What about you?
Vulture: No way. I don't do beaches. I'm going to buy some feathers from a duck and make myself a nice down jacket.
Cardinal: Nice! I'm down with that!
Vulture: That's horrible, Red. A joke that bad should make you feel embarrassed.
Cardinal: I know! I'm turning red…
Vulture: Stop it, Red! You're killing me!
That got us to thinking: how exactly do birds survive the coldest winters? You don't see any of them wearing jackets. You don't see heaters or blankets in the trees. Some birds fly south for the winter, but there are always birds around all year. How do they do it?
Birds have many different ways they adapt to life in the coldest months. Birds have a hard time in cold weather, because their body temperatures are higher than those of humans. Although exact body temperature varies by species, birds tend to have body temperatures around 105º F. So it's hard for birds to maintain that high body temperature in colder weather.
The feathers that cover birds are more than just for beauty. They provide warmth and insulation against colder temperatures. Many birds grow extra feathers in the months leading up to colder weather, so that they'll stay warmer when temperatures drop.
Some birds also have an oily coating on their feathers that also provides insulation, as well as waterproofing. Birds can also fluff up their feathers to create air pockets between the feathers. These air pockets provide even more insulation.
In the months leading up to colder weather, birds often increase their fat intake, too. Increased fat reserves can help even the smallest birds have extra energy, so they can generate more body heat.
Birds can lose a lot of heat through their legs and feet. Some birds have special scales on their legs and feet that reduce heat loss. Birds also sometimes stand on one leg or tuck legs and feet into their feathers to minimize heat loss.
On sunny days, you'll likely see birds bathing in the sun with their backs toward the bright rays. Even when it's cold outside, the sun can heat a bird's skin and feathers when they're sunning.
Other birds may instead go into a hibernation-like state called torpor. Birds in torpor lower their body temperatures to conserve body heat. This helps them survive the cold, but it also makes them more vulnerable to predators, since their reaction times tend to be lower in torpor.