Black-backed forktail

The black-backed forktail (Enicurus immaculatus), occasionally referred to as the black-throated forktail, is a forktail species in the family Muscicapidae. The species was described in 1836, from a specimen collected in Nepal. It is a medium-sized forktail, weighing between 25 and 29 grams, with a length of 20.5 to 23 centimetres (8+1⁄8 to 9 in). The species has a broad white stripe across its forehead. The crown, face, and mantle are black, while the bird's underparts are white, sharply divided from the black above. The wings are largely black with a broad white stripe across the greater coverts. The tail of the species, similar to that of other forktails, is long, graduated, and deeply forked. The tail is black with a white tip and three white bands created by shorter tail feathers. The beak of the bird is black, while the feet and legs are light pink, and the iris is brown. The species is monomorphic.

The black backed forktail is solitary, but is occasionally found in pairs or in family groups. It is described as a shy species. The bird breeds between March and June, building a nest of plant matter in holes or crevices in rocks and dead trees. Three eggs are generally laid, which are pink and spotted with red-brown. Both sexes build the nest and incubate the eggs. The species frequents fast-flowing rivers and streams in temperate forests and subtropical or tropical moist lowland forests. It is found in the Indian subcontinent and in some adjoining regions of Southeast Asia. It ranges across Bangladesh, Bhutan, India, Myanmar, Nepal and Thailand. It is generally found below 1,450 metres (4,760 ft) above sea level, but has been recorded as high as 2,600 metres (8,530 ft). Its precise range and population are unknown. It is classified as a species of Least Concern by the International Union for Conservation of Nature.

A medium-sized forktail, the black-backed forktail is between 20.5 and 23 centimetres (8+1⁄8 and 9 in). It weighs between 25 and 29 grams. The length of the wing has been recorded as between 8.6 and 9.8 centimetres (3+3⁄8 and 3+7⁄8 in) in the male and 8.6 to 9.0 centimetres (3+3⁄8 to 3+1⁄2 in) in the female. The bill extends 2 centimetres (3⁄4 in) from the skull, while the tail is between 12.4 and 12.7 centimetres (4+7⁄8 and 5 in) long.

The species has a broad white stripe beginning just behind the eyes and running across its forehead. The crown and mantle are completely covered in black feathering, which extends down to the upper forehead, face, scapulars, throat, and sides of the neck. The underparts of the bird are white, sharply delineated from the black of the throat. The lesser coverts and median coverts are completely black, as are the bases of the greater coverts. A broad white band runs across the wing, running across the greater coverts as well as the bases of the inner secondary and tertiary feathers. The highest tertial feather is white, and the inner primaries have white tips and the base of the secondaries are covered in a small white patch. The flight feathers are otherwise black. As with most other forktails, the tail of the species is long, graduated, and deeply forked. The feathers are black, with white tips, except for the outermost feathers, which are white. The tail has a white tip and three white bands created by the ends of shorter tail feathers. The beak of the species is black, while the feet and legs are whitish-pink or a light flesh colour. The iris is brown or dark brown.

The black-backed forktail does not exhibit sexual dimorphism, and has no known geographic variation in its appearance. Nothing is known of its moulting. Juveniles of the species lack the prominent white stripe across the forehead, and the areas that are black on the adult are sooty brown or dull black. Juveniles have a white spot behind the eye, and may have dark scales or speckles on its flanks, breast, and belly. The tail of the juvenile is usually shorter, while the mandible is yellowish, and the maxilla have whitish cutting edges.

The bird is similar to the slaty-backed forktail, but lacks the slaty back of the latter, and is also smaller in size. It also has a slimmer bill. The white band on its face is narrower than that of the otherwise similar white-crowned forktail: it is also distinguished by its white, rather than black, breast. Field identification guides describe it as being the same size as bulbul species. Its call is described as a short and whistled "tseep - dew" or "hurt-zeee". The two syllables of this call are sometimes produced separately, as a hollow "huu" and a shrill "zeee", which are somewhat higher pitched than the call of the slaty-backed forktail. It produces a two syllable call when disturbed. It also makes a call similar to that of the slaty-backed forktail, described as being reminiscent of a squeaky hinge. It has been described as occasionally producing a short song as well.