List the traits that characterize the class Mammals. What are the similarities and differences

List the traits that characterize the class Mammals. What are the similarities and differences between them and representatives of the Bird class?

The signs of mammals are, first of all, a body covered with wool or its evolutionary derivatives, developed glands, especially sweat and mammary glands, a four-chambered heart, non-nuclear erythrocytes. Also, the anatomical features of mammals are the external auricle and 3 auditory ossicles in the middle ear. Modern mammals are viviparous. Both birds and mammals are warm-blooded, almost all birds are capable of flying, unlike mammals. Also, birds are covered with feathers, and by the way of reproduction they are egg-laying.