How many chambers do the bird heart and the mammalian heart have? Concerning temperature maintenance what is the advantage of the double and complete circulation of these animals?

The bird and the mammalian hearts are separated into four chambers: right ventricle, right atrium, left ventricle and left atrium.

Birds and mammals are homeothermic, i.e., they control their body temperature. The four-chambered heart and the double circulation give the supply of more oxygenated blood to the tissues making possible a higher metabolic rate (mostly cellular respiration rate). Part of the energy formed by the cellular respiration is used to continue the body temperature.