Stop, look and listen
Blackbirds feed mainly on the ground. They run and pause, run and pause, run and pause. Each time they stop, they scan the ground for prey. If they see a worm, they search more thoroughly before moving on. This is because worms tend to live in small groups, so if a blackbird has found one another won't be far away.
As well as feeding on lawns, blackbirds love fallen leaves. They toss leaves away to find small edible creatures underneath. They will even do the same with snow! But how do they know to dig under that particular bit of snow or to look under a certain leaf? They listen, with very sensitive ears.