Birds are a diverse group of warm-blooded vertebrates found across the globe, with over 10,000 species identified. They belong to the class Aves and are characterized by feathers, beaks without teeth, and laying hard-shelled eggs. Birds range from the tiny bee hummingbird to the large ostrich. They occupy various habitats, from forests and deserts to wetlands and oceans. Major groups include passerines (songbirds), raptors (birds of prey), waterfowl, and seabirds. Birds play vital roles in ecosystems, including pollination, seed dispersal, and pest control. Many species are migratory, traveling vast distances between breeding and wintering grounds.