Every year, someone will call the local newspaper to declare that Spring has arrived - they have seen the first American Robin!
But, is the American Robin (Turdus migratorius) really a good indicator of the arrival of Spring?
The answer is maybe. It depends on where you live.
Most American Robins will migrate to the southern United States, Mexico, and Central America for the Winter, but some American Robins will stay in the northern United States year round if they can find food. It is likely that that majority of overwintering birds in the northern US are males that choose to stay to get a jump on the competition for breeding territories.
While many people think of Robins as suburban birds that hunt for worms in our lawns, they can actually be found across North America from the Gulf of Mexico to the Arctic Ocean and from the West Coast to the East Coast in all types of habitats. American Robins eat not only worms, but also insects and snails. There are records of them eating small snakes and even shrews. I have personally seen them eating large numbers of very small recently metamorphosed toads.
They also eat large quantities of berries and other fruit. In the Winter, they will sometimes gather in large flocks to hunt for berry-laden trees and shrubs in the woods. This switch of habitat from lawns to woodlands, makes them less noticeable in the Winter and causes people to assume that all Robins migrate out of the area. A look at eBird data will show many sightings will show sighting every month of the year for Mid-Michigan.
However, the number of American Robins increases dramatically in late March to early April as migratory birds either return or pass through the area.
So is seeing a single American Robin a good indicator of Spring if you live in the northern United States? Probably not, but if you suddenly see twenty of them in your lawn, it is probably an indicator that Spring has arrived.