Finally, it can sit down and cover all the bases. Many birds are able to control the amount of blood flow through their legs, which increases their ability to regulate temperature. The only danger comes in standing around on a cold day: with one foot tucked up and blood flow greatly reduced to the other, there is a possibility that the exposed leg will freeze. This can be countered by staying in a nest or, in aquatic birds, by going into the water. As long as the water is in a liquid state, the bird legs floating in it can’t freeze.