Birds can keep themselves warn without any external heat source which is not the case with reptiles and amphibians
Explanation:
Birds are able to generate heat means they are endothermic. They generate heat through various metabolic processes. They have air pockets beneath their feathers to insulate their bodies during cold temperatures. Feathers which are modified reptilian scales help birds to streamline their exterior body and structure feathers in a way that it insulates the body.
