Phaethornis hermits are small to medium-sized hummingbirds with dull colored plumage. All species of Phaethornis have very long, slender bills, which in many species are slightly curved, and also have long, graduated tails in which the central pair rectrices usually are particularly elongated. Green Hermit, also known as Guy’s Hermit, is a large Phaethornis with a slightly decurved bill and elongated, white-tipped central rectrices. The plumage is predominantly dark blue green, with gray underparts tawny markings on the face and throat.
Most other large species of Phaethornis, such as Long-billed Hermit (Phaethornis longirostris) and Great-billed Hermit (Phaethornis malaris), occur at lower elevations, and are mostly brown, in contrast to the largely blue-green coloration of Green Hermit. In western Colombia, Green Hermit overlaps with White-whiskered Hermit (Phaethornis yaruqui), which also is predominately green; White-whiskered Hermit differs by its dark green underparts, gray (not buffy) throat, more coppery crown, and also primarily occurs at lower elevations.
The following description is based on Wetmore (1968), except where otherwise noted, and refers to subspecies coruscus; see also Geographic Variation.
Adults are sexually dimorphic: females are more strongly patterned than males, and have more elongated central rectrices (see Measurements). Both sexes have a long, decurved bill, a tawny streak in the center of the throat, and elongated central rectrices with white tips.
Adult male: Upperparts bright metallic bluish green; crown duller. Rump and uppertail coverts blue; longer uppertail coverts turning black distally, with white tips. Bases of rectrices blue. Rectrices distally black; tips of central pair of rectrices narrowed, light gray with white tips. Wings, including the primary coverts, black with a purplish sheen. Side of head black; narrow submoustachial stripe and narrow central throat stripe both tawny. Center of breast and belly gray, sides of breast and flanks metallic green; center of lower belly washed with tawny. Undertail coverts mixed greenish blue and dusky gray, longer feathers tipped white.
Adult female: Similar to male, but upperparts somewhat greener. Tips to central pair of rectrices much longer, with narrowed white tip; lateral pairs of rectrices tipped white. Streak behind the eye, submoustachial stripe, center of throat, and lower belly ochraceous buff; rest of underparts dark gray, sides of breast and flanks more or less bluish green. Undertail coverts more extensively white.
Immature: Feathers of crown, nape, and lower back tipped with cinnamon; sometimes feathers across the entire back similarly marked. Sides of neck and breast with indistinct buffy tips. As they mature, young males begin to lose both facial stripes, becoming more easily distinguishable from adult females (Snow 1977).
No information available.
Iris: very dark reddish brown, black (Wetmore 1968, Robbins et al. 1985)
Bill: maxilla black; mandible bright red with a dusky tip, mouth lining bright red (Wetmore 1968, Stiles and Skutch 1989, Snow 1974).
Tarsi and toes: dusky gray, dusky flesh, pink (Wetmore 1968, Stiles and Skutch 1989, Robbins et al. 1985).
Total length: 11.5 cm (Ridgely and Greenfield 2001b), 13 cm (Hilty and Brown 1986), 13.5 cm (Hilty 2003), 14.5–15.5 cm (Schulenberg et al. 2010), 15 cm (Stiles and Skutch 1989)
Male (coruscus, Panama, n = 10; Wetmore 1968): wing length, mean 61.7 mm (range 58.8-63.7 mm); tail length, mean 50.5 mm (range 47.3-52.7 mm); culmen from base, mean 43.7 mm (range 41.8-44.9 mm)
Female (coruscus, Panama, n = 10; Wetmore 1968): wing length, mean 59.9 mm (range 57.6-62.3 mm); tail length, mean 63.9 mm (range 59.6-66.9 mm); culmen from base, mean 41.3 mm (range 39.6-43.0 mm)
Male (nominate guy, Trinidad; Snow 1974): wing length, mean 64 mm
Female (nominate guy, Trinidad; Snow 1974): wing length, mean 58 mm
Mass: 6 g (Stiles and Skutch 1989); male, range 4.5-5.5 g (n = 12; Robbins et al. 1985; female, range 4.0-5.5 g (n = 11; Robbins et al. 1985)