Answer:
The adaptation to different temperatures
Step-by-step explanation:
Mammals and birds share one common feature - they are vertebrates meaning that they have the vertebrata column or simply put, a backbone. In addition, unlike other animals, say the amphibians, these have the ability to regulate the body temperature through homeostasis. This is the ability to thermally regulate the body's temperature. This is done by the flow of the blood to the different parts of the body. Thus, the mammals and birds have evolve to share the common features.