Malabar Gray Hornbill Ocyceros griseus
Version: 2.0 — Published July 9, 2020
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Male: 42.5–47.5 cm length; 238–340 g (1). Female: 34.0–37.5 cm length (2). Small hornbill with gray and black-and-white plumage, a broad pale eyebrow stripe, and light gray underparts with fulvous undertail coverts. The casque on the bill is not protuberant; present only as a low ridge along the culmen extending to the bill tip. In males, the bill is dusky orange-yellow, becoming paler towards the tip. The skin around the eyes and on the throat is black; the eyes are amber. In females, the bill is more evenly horn colored, with black on the base of the lower mandible, and the iris is deep brown. Juveniles are similar to females with less extensive black on the bill. Juvenile Plumage is paler than Adult Plumage, with a fulvous tint to undertail coverts. The upper wing coverts have buffy edges and the flight feathers are edged white. The iris is gray (3) turning dirty yellow then brown (4) with relatively pale orbital skin.
The similar Indian Gray Hornbill (O. birostris) occurs in drier parts of the Indian subcontinent but may overlap in some intermediate zones along the Western Ghats mountains, such as in Dandeli and Kodagu, Karnataka (5) and in Kozhikode (6) and Nelliampathy foothills, in Kerala. The Malabar Gray Hornbill is distinguished from the Indian Gray Hornbill by the former's slightly smaller body size, whitish supercilium, lack of dark ear coverts, lack of protuberant casque on the bill, orange or ivory-colored bill (versus blackish), grayer plumage (paler sandy gray in Indian Gray Hornbill), incomplete white terminal band on darker tail (versus black-and-white tipped gray tail), and lack of white trailing edge to secondaries (visible in flight in Indian Gray Hornbill). Juvenile Indian Gray Hornbills do not have a prominent casque and may be mistaken for Malabar Gray Hornbills, and may be separated from adult Malabar Gray Hornbill by paler underparts lacking shaft-streaks, dark cheek-patch, paler brownish upperparts, and tail pattern.
Distinguished from Sri Lanka Gray Hornbill (O. gingalensis; found only in Sri Lanka) by grayish underparts (versus white), more prominent eyebrow, rusty vent, more orange bill, black circumorbital skin, oval nostrils (versus round), and lack of white outer tail feathers (as in older birds of Sri Lanka Gray Hornbill)(7).
The sympatric Malabar Pied-Hornbill (Anthracoceros coronatus) is much larger, with a large prominent casque, and black-and-white plumage.
In first-year birds, primaries are more narrowly pointed and the rectrices are narrower than in adult birds. Overall plumage color is a paler gray, with a fulvous tinge about the vent, and with conspicuous fulvous-edged wing coverts. Tail feathers are edged with pale gray, except the outer feathers that are tipped white (8).
Formative (First Basic) Plumage
Sub-adults may have only traces of pale edging on wing coverts and rectrices.
Definitive Basic Plumage
Grayish-white streaks on head, crown, throat, and upper breast; oval nostrils; long dark gray tail with terminal white band that is incomplete (lacking white in the central two pairs of tail feathers). White tail tip is usually visible as a terminal white band on the underside. In flight, has white wing tips (primaries) and narrow white carpal patch, gray wing lining and blackish underside of primaries (2). Females are smaller than males, but plumage is otherwise similar between the sexes.
Female confined in the nest reported to molt flight feathers and tail feathers, but not body feathers (9). Tail feathers noted as molting from inner rectrices outwards (3). Pattern of molt is known to be variable within and across hornbill species, and absence of full body molt suggests that the bird in the nest may not be as vulnerable as once thought (10). No information is available on patterns of molt in males.
Pale yellow bill, with commissure, gape, a patch on sides of lower mandible, and a triangle patch on culmen near the forehead all brownish slate in color (8). A chick taken on 5 May from the nest was observed on 11 July as having its bill horn with upper mandible darker, and lower mandible with greenish tinge (3). On 6 August, the young bird was noted as having two black lines running along either side of the culmen and the beak had developed a slight gap between the mandibles towards the tip, although the cutting edge still had no serrations (3).
Male. In adult males, the bill is dusky orangish brown becoming more evenly yellow at the tip.
Female. Bill is pale yellow to ivory colored, blackish patches or a line extends along the top of the culmen to the tip of the upper mandible, and black at base of lower mandible; small brown patch on the base of the upper mandible in front of the eyes; eyes dark brown with dark orbital skin.
Iris and Facial Skin
Iris is gray to brown. Facial skin is grayish; paler than adult.
Male has amber iris, while female has dark brown iris. Facial skin is black.
Tarsi and Toes
In chicks taken from the nest, feet are reported to have flaky-blue skin; the claws being horn and whitish below (3) .
Legs and feet dark greenish gray with black claws.
Table 1. Morphometric measurements of Malabar Gray Hornbill from various sources (mean and number of individuals given within parentheses, where available).
|Wing length, mm||185-201
(mean = 195, n = 7)
(mean = 212, n = 14)
|185-195 (n = 9)||205-218 (n = 3)||8|
|Bill length, mm||72-87
(mean = 81, n = 6)
(mean = 104, n = 11)
|Bill depth, mm||40||8|
|Gape width, mm||35.7 (3)||11|
|Tarsus length, mm||36-40
(mean = 38, n = 6)
(mean = 40, n = 7)
|Tail length, mm||188-205
(mean = 196, n = 6)
(mean = 222, n = 9)