In these sub-zero temperatures I've said several times in the past few days that I wouldn’t want to be a bird under these conditions. They are a lot tougher than they look!! How DO they survive those cold temps? Well, they do several things. First they eat a LOT of high calorie foods. That’s why it is important to keep your seed & suet feeders filled. Black oil sunflowers have the highest caloric value of the seeds. Peanuts & peanut butter & suets with those ingredients in them are very good cold weather foods. Besides eating a lot, you will notice that they are a lot puffier than normal. They are able to trap pockets of air between their bodies & the feathers to keep insulated from the cold. Birds such as chickadees & goldfinches shiver. Shivering raises their metabolic rate & in turn generates more body heat. Some birds roost together to share common body heat and they will tuck their legs or their beaks into their feathers for warmth. If it’s a sunny day they will sun themselves lifting their feathers slightly to feel the warmth on their skin. At night some birds enter a torpor state. This is when they reduce their metabolism which lowers the body temperature thus requiring less calories to maintain proper heat. It also makes them hungrier in the morning to replace those calories they lost so that’s why the birds flock to the feeders in the morning for food.
Soooo glad I’m not a bird! But I’m happy to help them out with lots of food & water in these cold temperatures!