This document describes the key characteristics of birds. It lists the main external features of birds, such as beaks, feathers, wings, legs and tails. It then provides some general information about birds - they are vertebrates that lay eggs, most have feathers and can fly, though some like penguins cannot, and they have warm blood, breathe through lungs and live mainly on land but some live in water. The document also lists examples of different types of birds.