Invasion!

I saw a rather interesting sight in the neighbourhood today. Dozens of robins. I've never seen more than three or four robins in one place at once, but today we had a whole flock of them. There must have been a couple dozen or more at times just in my backyard. I had no idea robins ever travelled in groups. Crows and waxwings can be seen in large groups at different times of the year here, so a large flock of birds in the neighbour isn't new to me, just robins in such a group.