Both the male and female Robin start singing in early autumn, after their moults are complete, to mark out their individual territories. They will hold these separate territories until around Christmas time when when the female will enter a male territory, and after some displaying for a few days they will remain together for about six months. I think I prefer the very quiet song, often sung from a hidden spot in a bush, to the loud song sung from the tree tops to ward off intruders. This quiet song will often go on uninterrupted for up to ten minutes at a time. I am sure this is sung just for pure pleasure as it can only be heard over a very short distance.