I didn't know robins migrated. Cool!

There are worse things which could invade :) (spiders, snakes, scorpions, alligators... come to mind)

Wow! I had never seen a robin in real life until I spent some time in the midwest. I never realized how huge they were. I had always imagined them being the size of a sparrow.

They don't always migrate. In warmer climates, they are year round residents. Migratory patterns tend to follow food sources. Their primary diet is earthworms, caterpillars and other insects so where soils freeze and temps get too cold for these to be much of a presence, they move south to find them or otherwise feast on fruits and berries.

Our "Robin" is actually a sort of thrush. The down side is the impressive din they make when they wake up the Crackadawn. The English Robin for which ours was names is a tiny thing totally unrelated. Robin babies have a walking phase when they leave the nest. Since Robins will raise several broods it is natures way of feeding cats, foxes and coyote while selecting the smarter robins. We would be up to our arm pits in robins elsewise. as Chisue is now. Some of our local birds stay but most of them leave. I am not sure where they go.

They must come here because I have them year-round. And I'm not that far south (Nashville, TN).

As a child in western PA most of our robins seemed to disappear over the winter so we assumed they migrated. However 65 years later I'm in Philadelphia and the robins stay.

Thank you, @patriciae_gw. I think you've just made sense of my confused idea of a robin's size.

Chisue, that’s so funny because I don’t see any in my yard. You must have better berries lol!

I think Robin feeding is part of the family cycle. They hunt and eat insects, worms, grubs and spiders when they have babies. I learned recently that a diet rich in spiders is necessary for some baby birds because it supplies Taurine. Yipes! They eat more fruit for themselves when the fruit matures. Ours are stoking up on blackberries and wild cherries. Watching young birds being transitioned to new food is always fun. You can see when the parents stuff them with seed and suet from the feeder out my back door they are incredulous that they are expected to eat this dreck. I wonder do the parents do the same for robin babies? Feed them fruit?

SW PA I think our Robins turned into snow birds. I haven't seen them for about a week. Before then for a couple weeks they were on a feeding frenzy in our backyard fattening up for their flight south. I do love seeing my first Robin in the spring. I know nice weather isn't far behind.

Most robins flee northern Ohio and reside here in central Ohio most of the winter. We have a milder winter, even if temps do fall to -14. I guess that's mild to some of you.

I wouldn't be concerned with the sudden appearance of those robins particularly if many were this year's young. They are on their way south. Robins leave Wisconsin before winter. They were flocking together and going south a couple of weeks ago. I did not see nay today. Robins that stick around late find themselves short of food and shelter and may not survive if a severe cold wave blows in.

When I was a boy, I lived in southern Illinois (100 mi east of St. Louis). Very few robins stayed over winter. Most were gone by Nov. 1. Even those late to migrate would leave in front of a cold wave. Robins were some of the earliest birds to return in spring.

https://bryanpfeiffer.com/2015/05/01/why-the-american-robin-is-a-badass-bird/

Lots of robins here too. Michigan's state bird is the Robin, so not uncommon.

They are still coming through in waves. This morning is busy with birds, zip-zip-zipping through the air in all directions, with a few spats between this bird and that one.

The spats may be our 'regular' robins, defending territory. We have them year-round, probably because our house is beside a deep ditch that was dug (1800's?) to drain the area for farming. It's at least 20 feet deep and ranges from ankle-deep in the summer to a torrent (with kayakers!) overflowing the banks during spring rains. Maps deem it 'a river'; I call it 'the ditch'. It stays warmer down there in winter, and, of course, there's water.

Last month we saw a young weasel -- a first for us in nearly 20 years here.