Sabrewings (Campylopterus) are large hummingbirds with a strong black bill. In males of most species, the shafts of the two outermost primaries are thickened, especially near the midpoint, and are recurved (forming the "sabre" for which these birds are named). Rufous Sabrewing is two toned, metallic green above and tawny buff below. There also is a distinct white spot just behind the eye. The tail is broad; the inner rectrices are green, but the outer rectrices are pale tawny basally, with a black subterminal band. Sexes of Rufous Sabrewing are similar.
The two toned, green and tawny pattern of Rufus Sabrewing is distinctive within its range, and this species is unlikely to be confused with any other hummingbird. Cinnamon Hummingbird (Amazilia rutila) is smaller, deeper rufous below with a rufous tail, and has a more slender bill that is mostly red. Rufous-breasted Sabrewing (Campylopterus hyperythrus) of Venezuela is completely allopatric, and has a more rufous tail.
The following description is based on Ridgway (1911). A large hummingbird, with a straight, stout, and broad bill. The shafts of the three outermost primaries (especially the outermost primary) are thickened basally, and, in the male, the middle portion of the shaft of the outermost primary is especially swollen.
Adult male: Upperparts bright metallic bronze green or greenish bronze, more bronzy on uppertail coverts; crown slightly darker and duller. Postocular spot white. Central pair of rectrices metallic bronze or greenish bronze; adjacent pair similar but with a broad but ill defined subterminal blackish band, and feathers tipped with cinnamon; outer pairs of rectrices basally cinnamon or cinnamon rufous on outer web, with blackish subterminal band more sharply defined, and with cinnamon tips; outermost pair of rectrices entirely cinnamous rufous on the outer web. Remiges dusky. The shafts of the three outermost primaries (especially the outermost primary) are thickened basally, and, in the male, the middle portion of the shaft of the outermost primary is especially swollen. Underparts cinnamon, slightly paler medially.
Adult female: Similar to male, but outer primaries not conspicuously thickened.
Very little information. In El Salvador, molt was detected in May (molt on body and on rectrices), and in October; birds in fresh plumage are reported from November (Thurber et al. 1987).
Iris: dark brown
Total length: 12.1-13.8 cm (Ridgway 1911), 12.5-14 cm (Howell and Webb 1995)
Linear measurements (from Ridgway 1911):
male (n = 5)
wing length: mean 73.5 mm (range 71-76 mm)
tail length: mean 49.2 mm (range 47.5-51.5 mm)
bill length: mean 26.3 mm (range 25-27.5 mm)
female (n = 4)
wing length: mean 71.5 mm (range 68.5-74.5 mm)
tail length: mean 49.7 mm (range 49.5-50 mm)
bill length: mean 26.2 mm (range 26-26.5 mm)
Mass: mean 7.5 g SD 1.1 g (range 5.8-9 g, n = 25, sexes combined?; Dunning 2008)