For the problem, we should not only know why, but also know why.
First of all, we should know that the human heart has two atria and two ventricles.
Birds need to fly, and they need more oxygen to provide aerobic breathing and generate energy during the flight. The key point is that the bird's heart is 2 atria 1 ventricle, which makes arterial blood (the blood pumped by the heart and flowing through the whole body is called arterial blood, which is characterized by high oxygen content; Blood flowing back to the heart can contain higher oxygen content than human blood.
More aerobic respiration produces more heat, so birds have higher body temperature than humans.