Description:  I immediately recognized it as a sapsucker.  Its overall brownish appearances with buffy-white barring and well-defined face marking quickly eliminated the most likely Red-breasted Sapsucker.

Overall impression: Very brown looking and washed out.
Head: Crown distinctly red with heavy brown streaking at forehead and around the perimeter.  Whitish supercillium going all the way to the nape.  No hint of red in the nape.
The red in the crown is atypical based on expected molt-timing,
but has been previously reported in a percentage of the 
population (Mlodinow, et al 2006).  Pyle (1997) indicates that
some juvenile males may have red in the crown from even 
before the pre-basic molt and become fully adult Dec-May.
Brownish eye-stripe and malar stripe.  Buffy-white throat. 
Malar stripe bleeding into brownish breast bib.
Breast: Upper breast smudgy brown.  Marks on mid-breast and
and flanks diffuse brown "V" marks.  Belly and under-tail
coverts washed lemony yellow.
Back: Medium brown with extensive buffy-white barring
that contributed to the general washed-out look of the bird
Wings: dark brown with white patch
Tail: dark brown with whitish barring

Red-naped Sapsucker is easily confused with Yellow-bellied and
separation can be problematic.  Most references agree that juvenile
Red-naped Sapsucker should have red in the nape by November.
Advanced molting of the red crown in Yellow-bellied Sapsucker is
far more common than delayed molt of the red nape in Red-naped.
One would also expect the crown and nape feathers to molt, more
or less at the same time.
Juvenile Red-naped Sapsucker should appear darker with less white
barring on the back.  This barring is most typically confined to two
parallel rows.  The general paleness (brown with buffy white) of 
the Royal Avenue bird combined with the absence of a red nape 
would seem to strongly favor Yellow-bellied over Red-naped Sapsucker.

I do not see any compelling reason to suspect this to be a hybrid.

Previous experience:  I have extensive experience with regularly
occurring Oregon sapsuckers.  This is the first Yellow-bellied I've
seen of this age-class and plumage.

References:

Mlodinow, S.G, J.H.Barry and C.D.Cox. 2006. Variation in Red-
naped and Yellow-bellied Sapsuckers. Birding, 38(6):42-51.

Pyle, P. 1997. Identification Guide to North American Birds (part 1).
Slate Creek Press, Bolinas, CA.

Shunk, S.A. 2005. Sphyrapicus Anxiety: identifying hybrid sapsuckers.
Birding, 37(3):289-298.

Sibley, D.A. 2000. Sibley Guide to Birds. Alfred A. Knopf, NY.

Winkler, H., D.A.Christie and D.Nurney. 1995. Woodpeckers: an
identification guide to the woodpeckers of the world. Houghton
Mifflin, Boston.