I have always thought that Robins are extremely territorial birds, so you get 1 per garden; maybe 2 in the mating season.
I currently have 3 regulars, who all arrive on the bird feeders at the same time, and 4th that turns up most days. There is no fighting so far. Is this a mated pair and last season's chick? Is there one lady with a large number of suitors? Any ornithologists able to shed some light on my (happy) multitude of robins?