This document provides information about the class Aves (birds). It discusses the key characteristics of birds like feathers, warm-bloodedness, and modified forelimbs as wings. It outlines the two subclasses of birds - Archaeornithes and Neornithes. It also describes several orders of birds like Anseriformes (waterfowl), Apodiformes (swifts and hummingbirds), Charadriiformes (shorebirds), Columbiformes (doves and pigeons), Falconiformes (birds of prey), Galliformes (chicken-like birds), Passeriformes (perching birds), Piciformes (woodpeckers and toucans), Procellariifor