No, birds are not mammals. Birds and mammals are two distinct classes of animals within the animal kingdom, each with unique characteristics and defining features.
Birds belong to the class Aves. They are warm-blooded vertebrates characterized by feathers, beaks, lightweight bones, and the ability to lay eggs. Birds have lungs and a respiratory system that allows for efficient oxygen exchange, essential for their high-energy activities, including flying.
Mammals, on the other hand, belong to the class Mammalia. Mammals are warm-blooded vertebrates with mammary glands, allowing females to nurse their young with milk. Mammals also typically have hair or fur on their bodies, and most give birth to live young (although there are exceptions like monotremes, such as the platypus, which lay eggs). Mammals have a variety of adaptations that help them thrive in different environments, including diverse methods of locomotion and specialized teeth for various diets.
In summary, birds and mammals are separate classes of animals with distinct characteristics and evolutionary histories.