why don’t penguins freeze to ice

Response from Natali[+++++]
In the cold, penguins, just like humans, reduce heat loss by reducing blood flow. However, reducing blood flow alone is not enough. It is important that blood from the feet does not flow cold back to the torso. German scientists have found that in the penguin's feet, arteries and veins are so tightly spaced that heat is exchanged between them. Cold venous blood flows from the feet to the torso and is heated in the process," says Dieter Adelung, professor at the Institute of Oceanography at the University of Kiel. Conversely, warm blood flows down the arteries and cools down. It comes to the feet already cooled. The penguin's feet are almost icy, their temperature is only slightly above zero. They're so cold that the ice underneath them won't melt. And since the ice doesn't melt, the penguin doesn't freeze. That's how these funny birds stay agile.