As energetic as their electric zapping call notes would suggest, Common Redpolls are active foragers that travel in busy flocks. Look for them feeding on catkins in birch trees or visiting feeders in winter. These small finches of the arctic tundra and boreal forest migrate erratically, and they occasionally show up in large numbers as far south as the central U.S. During such irruption years, redpolls often congregate at bird feeders (particularly thistle or nyjer seed), allowing delightfully close looks.