Question about robin behavior?

We have robins who have built a nest on the crutch of a roof drain under the overhang. There are currently three baby robins we can watch being fed. The nest is our rear door and if we open the door and come out, the adult robin (mom or dad) will fly from the nest and give an alarm sound (peek calls). I've noticed that the male will do this from nearby, keeping watch on us. But if the female is near as well, she seems to chase after the male, flying to wherever he is perched and nudging him, as birds do on power lines. She will keep moving him along whenever he perches. Anyone know why?