Can anyone tell me what kind of bird this is?
It appears to be a towhee. I am not sure which variety, that would depend on your geographic area. They are great fun to watch as they back kick through the dirt and scattered leaves searching for food. They are also often ground nesters that enjoy the seclusion and safety of a garden twig pile. However it is also common to find their nests in less secluded spaces, such as a shrub or the fork of a low tree branch.
The American robin and the Towhee look very similar to me, especially from a distance.
Hard to tell from the picture, but it could be a Spotted Towhee
Looking in my "Audubon Handbook Eastern Birds", it looks like it could be a Rufous-sided Towhee. I have had one that I have seen often at the bird feeder this winter.