This was very strange behavior. The robin chased the mouse up and down a 25 ft. pine tree twice over the period of several minutes like a hawk trying to snatch a bird. It really looked like the robin was trying to catch the mouse, not just chase him away. Robins are fiercely territorial. There must have been young ones around. In this photo, the mouse is making a run for it on the left of the photo as the robin is hot on his heels.