I’ve often wondered how the birds that stick around endure the winter. A friend recently piqued my interest on this subject so I decided to do a little research. Some of the information I found was fairly obvious but confirms my thoughts.

After a bit of looking around, though, I realized there was a lot that I didn’t know.

Birds’ body temperatures average a little bit higher than ours at 105 degrees Fahrenheit. They have to maintain that heat to survive.

One way they do that is with their insulating feathers. The down feathers closer to their skin have great insulating properties. That is why it’s a good stuffing for jackets and sleeping bags. The feathers hold warm air around the birds skin as insulation. Sometimes birds will fluff up their feathers so that the volume of warm air increases. This fluffing up is called “ptiloerection.”

Before winter, some birds will gorge on food to build up a good fat reserve and use that as fuel to keep warm as it metabolizes. In the winter, birds can spend the majority of the day seeking out high energy foods like the seeds and suet many people offer them at their feeders.

During blustery days, birds will take cover in sheltered areas to get out of the weather. Grouse often bury themselves in the snow for insulation and cover.

That was about the extent of what I knew or thought I knew up until now.

There is a whole lot more that wasn’t so obvious.

I’ve seen groups of birds huddled together to stay warm but I had no idea that they would also do that in birdhouses and nesting boxes.

To stay warm, some birds will also shiver but not like we do.

Their shiver is more like tiny muscle contractions so they don’t visibly shake. At night many birds will cool way down, by as much as 20 degrees or more. This regulated hypothermia or “torpor” slows the bird’s metabolism down so they burn less calories.

What about their legs and feet? Chickadee legs are so thin and frail looking. I’ve see seagulls stand on the ice for hours waiting for ice fishermen to leave their bait on the ice. It turns out that the scales on birds’ legs and feet are fairly good at preventing heat loss. Constricting blood flow in the legs can allow the temperature of legs and feet to descend to nearly freezing with some birds. You would think that would cause the bird to still get cold but some birds, like the seagull, have arteries and veins that prevent that. As the nearly freezing blood from the feet is returning to the heart it passes closely to the warm blood coming from the heart. This prevents the bird’s core temperature from significantly dropping. Who knew that?

Hopefully you learned something new from this. I know I did.

If you have a feeder you’re definitely helping these little guys get through this. Enjoy the birds!