UPDATE: This is a female redwing blackbird. Duh. Since she was always with the males, I should've known.
But I don't know what it is! These are photos, both good and bad, to help identify it. The worst photos have just enough color that I hope it can help. The redwing blackbirds give perspective on size.
There is another photo of these birds here.
I really like the photo above because of the movement in it. Look at the "split" in the female's tail. That is new to me.