Female blackbird with a russet breast

We've recently spotted a new female blackbird feeding at our bird table. She is easy to identify as a blackbird, but she has a russet breast, and looks like a cross between blackbird and Robin, though the russet breast doesn't extend to the face, stopping at the throat. The whole of the rest of her plumage is standard female blackbird livery. 

The russet breast is subtle; you have to look carefully to see it. But since our bird table is at eye level, and close to the kitchen window, we can watch her at our leisure.

I'll try to get a photograph, but is this colouring usual?