Fox Sparrows are somewhat non-descript, but in flight their rufous tails show and that may be the origin of the connection to a fox, or at least a fox's color.  The breast is heavily streaked on this brush and woody undergrowth avian. 

Males defend the territory toward other species, too.  The female does the work of brooding the fledglings on cool days. Females are also primary nest builders, picking grass, moss, lichens, fur, feathers and adding some finely-shredded bark. In early spring they may be seen hanging out around feeders.