First of all, I want to once again thank Marlene Condon for posting the sapsucker photo. I have learned a lot about sapsuckers during the past few days. I was curious if the red coloring on its nape might be a result of pigment from its diet, such as the orange tail coloring on Cedar Waxwings after eating red honeysuckle berries, and noting that the berries on the autumn olive are bright red. So I sent an email to Steve Rottenborn asking his opinion. For those of you who don't know Steve, he is an expert birder, has a Ph.D. degree, is formally from central Virginia, and is currently a Principal, Senior Wildlife Ecologist living in California. He is also a co-author of "Virginia's Birdlife", (the Goldbook annotated checklist). Steve also follows the VA birding list server when he can. With his permission, his response follows:
"Yes, I've been following that thread on the interesting Crozet sapsucker. I saw the initial report last fall, and knowing that Yellow-bellied Sapsuckers can have red on the nape, I hoped there would be some good photos for VARCOM to evaluate. The photo accompanying the article is very good, and in my opinion, it suggests that the bird is not a Red-naped.
I'm well aware of the danger of relying on a single photo to make a tough identification, and if there are other photos available, I'd be interested in seeing them. In this case, however, there are enough characters visible in the photo that I doubt my opinion would change with more images.
First, regarding the red nape - a YBSA with that much red on the nape is very unusual. The following is from a draft (I can't put my hands on the actual article at the moment) of a Birding article on sapsucker ID (Mlodinow, Barry, and Cox. 2006. Variation in Red-naped and Yellow-bellied Sapsuckers. Birding 38:6 42-51.):
"Yellow-bellied Sapsuckers tend to lack red on the nape, though a surprising number - mostly males - have at least a couple red feathers there (Kaufman 1990). Of 365 adult Yellow-bellied Sapsuckers at FMNH, CMVZ, UWBM and PSM, 16 (4.4%) had some red nape feathers, with five (1.4%) displaying sufficient red that it likely would have been apparent in the field. S. Rottenborn (unpublished data) found five of 62 (8.0%) adult Yellow-bellieds to have some red on the nape, two (3.1%) of which were judged to have sufficient red as to be visible in the field. Of 120 adult male Yellow-bellied specimens studied by Robbins et al. (2005), 23 (19%) showed red on the nape, but only two (1.7%) of these were within the range of an adult male Red-naped. Among 243 first-cycle birds at the FMNH, UWBM, PSM, and ANS seven (2.9%) showed at least one red nape feather, including two females, and including two birds collected as early as October. Only one (0.4%) had enough red on the nape that it would likely have been evident in the field: a male collected on 18 October in Philadelphia (ANS #177237). None of the 55 first-cycle Yellow-bellied Sapsuckers reviewed by S. Rottenborn (unpublished data) had red nape feathers."
So, whether the Crozet bird is a Yellow-bellied or something else, Marlene certainly found an interesting and unusual bird.
As for your question about whether the red on the nape may be related to the bird's diet of autumn olive - a study of "Yellow-shafted" Flickers found that consumption of bush honeysuckle fruits caused the appearance of red pigment instead of yellow on flight feathers (Hudon et al. 2017. Diet explains red flight feathers in Yellow-shafted Flickers in eastern North America. Auk 134:22-33), so I suppose something similar could occur with other woodpeckers and other fruits. However, the color of the nape on the Crozet bird should not be related to what it was eating in Marlene's yard. Any effect of diet on pigment in the feathers would be expressed as the developing feathers are grown, not in already-acquired feathering. Unlike immature YBSA, which undergo much of the pre-basic molt on their wintering grounds, adult YBSA (and the Virginia bird is an adult) molt before fall migration, so the red feathers that grew in on this bird's nape were likely acquired before the bird started eating autumn olive berries in Crozet.
Aside from the nape, several features point to YBSA rather than RNSA. On the back, the pale feathering is more extensive (laterally), covering more of the back, than is typically the case in RNSA. Also, the pale areas on the back consist of longitudinally short pale bars rather than longer pale blocks that occupy more area of each feather as would occur on a RNSA. YBSA therefore have backs that are more extensively covered by short pale bars, whereas RNSA have larger/longer pale areas that are confined more toward the center of the back and that often, especially on males, form two pale stripes. Within each species, females have more extensive pale areas on the back than males, and I think immatures may have more extensive pale areas than adults. This bird's back looks typical of an adult male YBSA.
YBSA tend to have broader pale supercilia and malar stripes, and consequently a narrower black auricular stripe, whereas RNSA tend to have broader black auriculars and narrower pale supercilia and malar stripes. There is certainly variation within each species, but the Crozet bird looks typical of a YBSA.
The black frame on the throat of the Crozet bird appears complete, based on this single photo, as it does not appear to have red feathering encroaching into the black frame. That points to YBSA. However, based on this one photo, the black frame appears pretty narrow, not as broad as on some YBSA. I've seen some otherwise typical RNSA that have a black frame that is about as broad as on the Virginia bird, though on those RNSA, there were scattered red feathers among the black ones, breaking up the frame to some extent.
I have spent a lot of time over the years pondering sapsucker ID, but on several occasions I've provided an opinion only to be later convinced by others that I was probably wrong. So, take all this with a grain of salt - it's just my opinion. I think the Crozet bird could possibly be a pure YBSA with an unusually red nape, but it could also be a hybrid RNSAxYBSA. I would not consider this an acceptable RNSA because too many of its characters point to YBSA. If nothing else, it's an interesting bird, and another data point in our experience with the range of variation in Red-naped/Yellow-bellied-type sapsuckers.