Some America Robins migrate but if you look at the range map you’ll see that there are winter populations of robins in most states year round. Robins are surprisingly hardy birds, capable of surviving temperatures well below zero. But that doesn’t mean sightings are common.
After nesting season has ended, they usually form large nomadic groups that roost at night in the woods. Their diet changes from mostly worms and insects to fruit, nuts and berries. I’ve seen them devouring our crab apples, Mountain Ash tree berries, and sometimes under my feeders looking for nuts. They also appreciate open water in the winter. If you have a pond or heated birdbath they may show up for afternoon drinks.
The Eastern Bluebirds also gathers in large family flocks at the end of nesting season and live more in the woods. They forage on fruit, nuts, and berries. If you have fruiting trees or bluebird feeders and a reliable source of water, you may host the bluebirds year-round.
We often think of migration as birds traveling thousands of miles south to winter in a tropical climate. There are also partial migrants, meaning only part of the population migrates annually. American Robins can become nomadic. During heavy snowstorms they may move further south to find food only to move back when the weather clears.