Answer: nightingales

AnswerCrossword Clue
NIGHTINGALESSweet singers.
NIGHTINGALESNocturnal singers
nightingalesNIGHTINGALE, a small bird of the thrush family, celebrated for its song
nightingalesA small European thrush with drab brownish plumage, noted for the rich melodious song of the male, heard esp. at night in breeding season