Just now ,as I am typing this I hear not one but two sounds -the bigger and more strident one from the nearby  back garden and the second one probably from a distance in the front lawn which appears slightly in baritone. As the dawn breaks where does it disappear ? Apparently it does not .It continues to make the racket through the morning .Only you do not get to hear it as the sound level in the city goes up with people getting up from bed and going about their daily activities.