Birds are members of the animal kingdom; they have their own class, known as Aves. (A possible origin of the word “bird” is thought to be the Old English brid, which originally referred to the young of animals.) Birds are vertebrate animals, warm-blooded, reproduce by laying eggs, and have feathers and beaks. They have four limbs, with the front two limbs modified into wings.
While you definitely wouldn’t have heard “Polly want a cracker!” during the Cretaceous period, evidence has been found suggesting an ancient ancestor of the parrot may have existed during that time (iStock).