The Red-necked Woodpecker is a large woodpecker with a striking assemblage of distinctive black, red and rufous colored plumage. The crest and neck are long. The bill is large, chisel-tipped and pale grayish-white to ivory-colored. The eye is yellowish-white. In both sexes, the upperparts are entirely black. The head and neck are mostly red. Females vary from males mainly in having a black-bordered, broad whitish stripe from the base of the bill to below and beyond the eye. Underparts are plain red to rufous-cinnamon or rufous-chestnut colored.
The distribution of Red-necked Woodpecker overlaps with large portions of the ranges of two other large woodpeckers, Crimson-crested Woodpecker (Campephilus melanoleucos) and Lineated Woodpecker (Dryocopus lineatus) but habitat preferences differ between these three species at most sites. Red-necked Woodpecker is easily distinguished from both of those species by its uniform black back and rufous underparts (Hilty and Brown 1986).
Red-necked Woodpecker habitat is adjacent to habitat of Crimson-bellied Woodpecker (Campephilus haematogaster) in Ecuador and in eastern Peru, places where they may share limited elevational overlap (Schulenberg 2007: 288) (See also, e.g., range maps for each species at NatureServe website). It is most similar in plumage pattern to Crimson-bellied Woodpecker, but Red-necked Woodpecker lacks the black throat and striped facial pattern of that species.
The Red-necked Woodpecker is sexually dimorphic. Differences between sexes are visible in head plumage. These differences are very similar to those present in two other members of the same Campephilus genus, the Cream-backed Woodpecker and Robust Woodpecker. The following description is from Winkler et al. (1995) and Short (1982).
Both sexes: Crest and entire neck to lower breast or abdomen bright red. Upperparts entirely black to brownish-black. Wings are black with extensive rufous on inner vanes of flight feathers. Flight feathers rarely bear rufous to whitish tips to primaries. Underwing is rufous with darker coverts and blackish tips and trailing edge. Tail is black above with four strong feather shafts; brownish-black below. Underparts are unbarred, red and rufous to rufous-cinnamon below.
Adult male: The entire head and neck is red with an inconspicuous black-and-white spot on the lower, rear feathers that cover the bird's ear opening.
Adult female: Lacks black-and-white oval on ear coverts. Females have a black-bordered, broad whitish stripe from the base of the bill to below and beyond the eye. Chin is black.
Immature: Juveniles resemble adults but are duller, with blacks appearing more brownish and reds more orange in color. Immature males have a whitish moustache, usually showing some red feathers too. Immature females have more black in facial markings than adult females.
Annual molt times that vary depending upon locations and subspecies are detailed in Short (1982) as follows. (See the next section below for subspecies descriptions).
C. r. rubricollis, July to October in the Guianas, June to December or even February in Venezuela, September in Colombia and July to December in northern Brazil.
C. r. trachelopyrus, July to February in Peru.
C. r. olalle, September to February in Bolivia, June and July on the Tapajoz River, August and September on the Xingu River, November and December on the Tocantins River, and September to February along the lower Amazon River.
Bill is long, chisel-tipped and pale grayish-white to ivory-colored. Eye is yellowish-white. Legs and feet are blackish-gray or olive. Forth toe is longest (Bock and Miller 1959:21-22).
Wing: 169-206 millimeters (Short 1982).
Tail: 115-121 millimeters, in trachelopyrus (Winkler et al. 1995).
Bill: 42-47 millmeters, in trachelopyrus (Winkler et al. 1995).
Weight: 178-236 grams (Short 1982).