Post #14224

Why is it not cold for birds to run barefoot in the snow and swim in icy lakes? “What a fool,” you think, leaving the entrance in winter. There is snow and ice all around, your toes curl up in your winter boots from the memory of the weather forecast for today. And then you notice how the neighbor’s granny feeds the pigeons, sparrows and other feathered brethren. And all these birds are completely barefoot! How can that be? Why do all kinds of feathered cabbage rolls walk in the snow, sleep on metal cornices, and ducks also swim in icy water without the slightest harm to their health? Let's start with the fact that barefoot birds can still freeze their paws at very low temperatures - nature does not provide absolute protection to anyone. However, it can provide a lot of interesting benefits that, when used correctly, help animals survive in not very favorable conditions. And the first bonus that evolution provided to our frost-resistant friends is thick skin on their paws. The birds' legs are covered with shields made of dense leathery plates, which act as a heat insulator. There are almost no muscles in the paws of birds (they are mainly in the body, they control the paws through tendons), little fat and nerve endings. Less fabric = less heat loss and less sensitivity to cold. Well, let's say, at -2 or even at -5 this will help. But what about at -30? Let's remember: how is the body heated? Hot blood from the body goes through the arteries to the limbs, where it cools down and returns through the veins to the body to warm up. Remember how your fingers get numb in the cold, preventing you from tying your shoelaces? It's all about vascular spasm - your body, conserving heat, automatically reduces blood flow in the extremities. Such vascular spasm reduces the performance of the arms and legs, but protects the internal organs from hypothermia. The body, as it were, locks the heat in the body, not releasing the hot blood to cool “to the periphery”, so that you do not become completely stiff. So, if the legs and arms of people literally freeze from cold due to a lack of hot blood in the extremities, then birds have overcome this limitation! They regulate the blood flow in their paws themselves, so their limbs don’t get cold at all! The fact is that the arteries carrying hot blood are tightly intertwined in the bird’s legs with veins that return cold blood to the body. The average temperature of arterial blood is 40 degrees, and cold venous blood can drop as much as 3! If such cold blood entered directly into the bird’s body, it would quickly become numb. But venous blood uses the arteries running near it like a battery, warming up on its way into the body. A pigeon or a duck decides for itself whether to contract or dilate blood vessels, but you cannot decide which socks to wear today. Shame on you, man! Photo 5 - Foot of a polar owl. So they really have to insulate themselves in extreme winters. - - - - - We have a huge gr