Birds are warm-blooded, feathered animals that belong to the class Aves. They are characterized by their beaks, wings, and ability to fly (although not all birds can fly). There are over 10,000 known species of birds, ranging in size from tiny hummingbirds to large ostriches.

Birds are found all over the world, in a wide range of habitats, from forests to deserts, and from mountains to oceans. They play important roles in various ecosystems, such as pollinating plants, spreading seeds, and controlling insect populations. Birds are also known for their beautiful songs and bright, colorful plumage, which they use for communication and courtship.

Birds are adapted for flight, with lightweight bones, strong muscles, and a unique respiratory system that allows them to extract oxygen from the air more efficiently than mammals. Their wings are highly specialized and can be used for a variety of functions, including hovering, soaring, and diving.

Birds lay eggs, and their young are born in a highly undeveloped state, relying on their parents for food and protection until they are able to fend for themselves. Many bird species also migrate long distances, traveling thousands of miles to breed, feed, or escape harsh weather conditions.

Birdwatching, also known as birding, is a popular pastime, with enthusiasts observing and studying birds in their natural habitats. Birds are also kept as pets, such as parrots and canaries, and are bred for food in some cultures.