secretary bird, common name for a long-legged African bird, Sagittarius serpentarius, related to the hawk and about 4 ft (122 cm) tall. Its crest of black feathers suggested the quill pens behind the ear of a 19th-century male secretary. The bird hunts on foot, zigzagging toward its prey and flapping its wings, and is valued as a destroyer of snakes and other reptiles. Secretary birds are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Falconiformes, family Sagittariidae.