The song is loud, with an impressive range of whistles, trills and gurgles. Its song is particularly noticeable at night because few other birds are singing. This is why its name (in several languages) includes "night". Only unpaired males sing regularly at night, and nocturnal song is likely to serve attracting a mate. Singing at dawn, during the hour before sunrise, is assumed to be important in defending the bird's territory. Nightingales sing even more loudly in urban or near-urban environments, in order to overcome the background noise. The most characteristic feature of the song is a loud whistling crescendo, absent from the song of thrush nightingale. It has a frog-like alarm call.