First, birds and mammals are recently evolved and are closely related. They share many genes and have the same basic anatomy. Second, birds are very similar in size, habitat, and feeding whereas mammals are extremely diverse. The main reason is that flying involves many special adaptations that limit how birds look.

The endotherms primarily include the birds and mammals; however, some fish are also endothermic. If heat loss exceeds heat generation, metabolism increases to make up the loss or the animal shivers to raise its body temperature.

Virtually all mammals are endothermic. Endothermy is the ability of an organism to generate and conserve heat in order to maintain a stable, warm body temperature. This ability is commonly referred to as warm-bloodedness.

Birds might be conscious and self-aware like humans, groundbreaking study finds. If you, like me, believed pigeons and other avian beings are stupid, you’re wrong. In a groundbreaking discovery presented in two papers, researchers found that birds are not only smart, but could be conscious and possess self-awareness.

Snakes, lizards, turtles, crocodilians, and birds are reptiles. Like all vertebrates, reptiles have bony skeletons that support their bodies. Scales help prevent reptiles from losing water through their skin. The leathery or hard shells on their eggs protect the young from drying out while they grow inside the egg.

No mammals have feathers, and most of them have skin covered with hair. Birds, on the other hand, use these feathers to fly, but not only that, but they also help them keep their bodies warm. Another physical trait that makes birds wildly different from mammals is the fact that they have beaks and do not have teeth.

Bird, (class Aves), any of the more than 10,400 living species unique in having feathers, the major characteristic that distinguishes them from all other animals.