I'm not an expert on birds. But saw something the other day that I thoght was interesting. I live near downtown Minneapolis along the Mississippi River, and have noticed a big group of 100-200 robins hanging out on a steep south facing slope. I thought these guys all migrated south and only came back to tell us it was spring. In addition. Just 100 yards away on a flat colder open area by the river I saw about 100 Snow Buntings flitting about. I thought these guys only came here to let us know it was deep winter. I found it surprising to see large groups of classic summer and winter birds hanging out so close to each over. Thought I would share with more serious birders in case interested.

Robins are only partially migratory and move on when their food sources dry up. Like when everything is covered up in deep snow. I've seen them all winter long in the Twin Cities area during many mild winters. Check out this Cornell website.

In addition to what inspector said, robins behave differently in winter than in summer, namely, in winter they hang out in very large flocks like the one you saw. For that reason, most of the time in winter you don't see any at all, even if hundreds are nearby. You have to be in the right spot at the right time to see them in winter. Whereas in summer they are dispersed on breeding territories and singing. So sometimes when they "arrive" in spring, they are just coming from a few miles a way and dispersing and singing all over the place. That said, they do tend to move somewhat south in winter. I think there are none (or almost none) in the area around Ely where I live now.

Snow buntings also hang out in large groups in winter. So I'm not real surprised you saw big groups of both near each other, though I have never seen that, and it is pretty cool.

quote Ho Ho: "So sometimes when they "arrive" in spring, they are just coming from a few miles a way and dispersing and singing all over the place.
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So while the snow buntings probably migrated here from the arctic circle, the robins may have simply migrated downtown from the suburbs for the winter? That's interesting - I appreciate both your responses. Like I said, I don't really know birds well, but I am regularly amazed by the range of birds I see right along the river in downtown minneapolis.

Yep, it's true.

Some of the Robins could also be from further north . . . they are gone here now . . .