Looking out of the kitchen window this morning I saw four goldfinches feeding on the seed heads of Verbena bonariensis. This is the very reason I never cut these plants down in autumn. Goldfinches are rare visitors; I saw them occasionally in my old garden, where I had some teasels. If the big freeze goes on much longer, I may see redwings, which only come south in the bitterest of weather. Edit I've just checked and redwings were last seen here in December 2010.
Coincidentally, I’m currently reading a wonderful book: A Sweet, Wild Note by Richard Smyth. It’s all about birdsong and our relationship with it. I’ll write some more about it later, I hope.