A nightingale is a small brown bird. The male, which can be heard at night, sings beautifully. a small bird that sings very beautifully, especially at night. Any of several small Old World thrushes (family Turdidae) renowned for their song. The name refers in particular to the Eurasian nightingale (Erithacus megarhynchos), a brown bird, 6.5 in. (16 cm) long, with a rufous tail. It sings day and night from perches in shubbery. Its strong and varied song, with prominent crescendo effects, has been regarded for centuries throughout Europe and Asia as the most beautiful of all birdsongs. The thrush nightingale, or sprosser (E. luscinia), is a closely related, more northerly species with slightly darker plumage. The term is also applied to other birds with rich songs (e.g., the wood thrush)