Birds belong to the animal group known as Aves. This class of animals is characterized by feathers, beaks, and the laying of hard-shelled eggs. Birds are warm-blooded vertebrates that have wings, although not all birds are capable of sustained flight.
The Aves class is further divided into various orders and families, which encompass thousands of species ranging from sparrows to eagles. One of the key adaptations of birds is their lightweight skeleton and the presence of feathers, which aid in flight and insulation.
In summary, when we refer to birds, we are specifically talking about members of the Aves class within the broader animal kingdom, distinguished by their unique anatomical and physiological features that enable them to thrive in diverse environments.