American Robin Okay, robin watchers. The American Robin is a territorial bird.
Males sing to declare their territorial boundaries.
Both males and females aggressively defend their territories, keeping other robins at a distance. Sometimes robins even bash themselves against windows and car mirrors trying to chase off their own reflections. The American Robin is a flocking bird that doesn't usually defend a territory. Hundreds of robins can join together in a single mountain ash or crabapple tree, feeding together and finding security in numbers. Actually, BOTH are true, depending on the calendar.