Pacific North West morph Song Sparrow. This morph is often confused by East coast birders with the Fox Sparrow because they are use to the paler East coast population of Song Sparrows. The PNW Song Sparrows tend be very sooty to brick red unlike their central and East coast cousins. So basically the closer you get to the PNW, the Sootier the Song Sparrows.
If you were to see the chest of this bird you would notice streaking. On a Fox Sparrow, this streaking would be made up of tiny chevrons (sometimes lined up in streaks, sometimes not).
Unless you have The Sibley's Guide to Birds, more than likely the guide won't have the PNW morph of the Song Sparrow. The Sibley's Guide to Birds is the best, most comprehensive bird guide on the market. If you don't have one, get one
If a bird has several morphs, the normal guides (Peterson's guides etc.) will typically show only the most common morph. Sibley's shows them all (plus hybrids). Sibley also looked at many different birds of the same species before making his paintings and averaging them together. The guides that rely on photos tend to show only what that one bird looked like, not what the average population (or sub-populations) should look like.