It is quite mind blowing that this is polyphyletic on mammals and birds, what can't parallel evolution achieve??
Phylogenetic tree of the vertebrates
. Source. Highlights how birds should obviously be classified as reptiles. Articles by others on the same topic
Warm-blooded, or endothermic, refers to a characteristic of certain animals that can maintain a relatively constant body temperature regardless of the external environment. This ability allows warm-blooded animals to remain active and functional in a variety of climates and conditions, as they can generate and regulate their body heat through metabolic processes.