Your American robin is wonderful. They do like trees, but I’ve seen even more on the ground in search of worms and other bugs for their next meal.
How do robins hunt for worms? Worms must be hard to find, right? I read that robins mostly use their very good vision. They can spot the tiny end of a worm as it pokes out of the dirt. They can also see small changes in grass as worms move about just below the surface, which tells them that a worm is there. It would be like wiggling your toes under a blanket. To be sure, they tilt their head to better see with one eye. Then they strike.
They also have very good hearing. As worms wiggle about, they move soil so that small bits of dirt rub together. This makes noise that is way too faint for us to hear, but it’s easy-peasy for robins. I’ll be excited to see them come back this Spring. Look out, worms!