The pasture around my house was covered with robins. Today It appears that the Robin migration should soon be underway. If robins over-winter in your area, please report the first wave of migratory robins passing through your region. Although you can never be certain, the robins' behavior reveals helpful clues. During migration, robins travel in flocks and usually don't stay in one place for long periods.
Migrants generally seem more wary than do resident birds.
For example, sudden movements such as slamming a door will cause them all to take flight. Right now we mostly see single birds at a time. We know they are not the same ones of course. The winter birds are huskier and larger in size than the summer birds. The summer Robins left around Halloween.