We live in Iowa and last year on Feb. 15, hundreds of robins came to our house. They stayed a few weeks. They would leave our area sometime in the am but always return around 6:10 pm each evening. I had never seen that before. We always see a few in the yards each spring but not flocks of them.
I saw a flock of robins like that once in Colorado. It was the strangest thing. The ground of our local park was literally covered with them. There probably wasn't a square foot of the grass without a robin on it. Haven't seen anything like it since. I did have quite a few in the yard at once a couple of weeks back, but nothing like that.