Are birds cold blooded like snakes and fish?

living birds endotherms, meaning burn energy internally maintain high body temperature. in fact, birds maintain higher body temperature mammals. therefore birds feels warm our hands. if anything, our own blood colder blood of birds. if our blood warm birds, having fever.

said, there indeed birds closer snakes in not being endothermic. birds had growth rings in bones, other ectothermic animals. birds known enantiornithine or opposite birds, , different modern birds in having leg bones fuse opposite direction modern birds. successful, , dominated earth during age of dinosaurs, when climate warmer today. because warm, there no need waste energy maintain warm body temperature. warm blooded without burning energy stay warm. further, if there burn energy stay warm, may overheat after exercising. in fact, 1 of reasons why lions can chase zebra short period of time because build heat cannot keep chase. therefore being endothermic in hot climate disadvantage. theropod dinosaurs, because ecotherms, can chase prey longer periods of time without overheating.

enantiornithine birds, despite success, unfortunately wiped out @ end of cretaceous, when giant meteor struck earth , created world wide forest fires , high atmospheric temperatures, killing dinosaurs , opposite birds. modern birds survived mass extinction because unable compete , forced occupy shoreline habitats, near edges of seas, today's sandpiper. because shoreline habitats cooler, evolved endothermy in order maintain high enough body temperature survive. because shoreline habitats cooler, spared heat , survived. living birds evolved small group of survivors, , reason why living birds endotherms. other groups of animals survived because lived in or near water include crocodilians , turtles.

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