Robins eat invertebrates such as beetles, earwigs and ants, found on the ground and on the woodland floor. They don’t dig for these or turn over leaf-litter, instead they must wait until the creepy-crawlies show themselves on the surface – in other words, until the prey makes a mistake. When robins perch on spades they are watching the ground below for food to break cover, and then they pounce upon it.
They also feed by hopping along the ground, hoping to cross paths with moving prey. For this sort of patient feeding to work, robins need privacy and a lack of disturbance. And for this they need a territory. If they don’t defend their territory vigorously, their foraging will keep being disrupted and they will starve.
So, robins cannot tolerate intrusive competitors and must sometimes fight them to the death. Dunnocks often feed in similar shady corners to robins and are summarily evicted.
Even wood mice have been attacked by robins trying to forage. People, though, present opportunity for robins. By tilling the soil while gardening, human beings unearth an army of invertebrates into the open. That’s robin heaven; no wonder they are tame!