Slaty-backed Forktail

The slaty-backed forktail is a slim, medium-sized forktail between 22 and 25 centimetres (8+5⁄8 and 9+7⁄8 in) long, and weighs between 26 and 38 grams (0.92 and 1.34 oz). It is coloured slate-grey, black, and white. The bill is black, while the feet of the bird are a pale pinkish or greyish colour. The iris has been described as dark brown, though it has been recorded as black in certain specimens. It has a black throat and a narrow white stripe across its face till just behind the eyes, sometimes describe as a white mask. The white stripe sometimes includes a white eye ring, which may be either complete or partial. Its ear coverts, chin, and face are also black. The forehead, crown, sides of the neck, and the scapulars are slate grey. It has black wing-coverts, a white patch at the base of the primaries, wide white bars on otherwise black wings, and also a large white patch on its rump and lower back. The bases of the flight feathers are white, which is occasionally visible as a little additional bar on the wing. The tail of the bird is long and evenly graduated, with a deep fork. The tail is largely black except for a white tip. It also has three white bands along its length, formed by the white tips of shorter tail feathers. The juvenile of the species lacks a white forehead, is brown above, and has dark scales on its breast. …

The slaty-backed forktail is found near fast-flowing water bodies in tropical and sub-tropical montane broadleaf forests, as well as near cultivated areas. These include rocky streams and rivers, including broad rivers and valleys in plains areas. A 2000 paper studying birds in northwest India and Nepal found that the incidence of slaty-backed forktails decreased with altitude. The study also found that the slaty-backed forktail had a preference for streams that were bordered by dense and complex vegetation, and had firm and stable banks of earth. They also preferred streams with finer grained sand on the bottom, and with "pool–riffle sequences." More rarely the bird is seen in secluded areas of the forest, and on the sides of roads or trails near the water. In winter months it has been observed to move from the mountains into foothills and plains areas. The species is found in the central and eastern Himalayas, from the Indian state of Uttarakhand in the west to Myanmar in the East, including Nepal, and Bhutan. It is a vagrant in Bangladesh. It is also found in southern China, in southeast Tibet, and in the provinces of Sichuan, Yunnan, Guizhou, Fujian and Zhejiang, and possibly in Hainan. Its range in South-East Asia includes Thailand, Vietnam, Laos, Cambodia, peninsular Malaysia, and Hong Kong. In Hong Kong, it is only an occasional winter visitor or highly uncommon resident. …

The slaty-backed forktail breeds between February and July; the breeding period does not appear to vary across its range. It builds a nest with materials including bryophytes, leaves, and grass. The shape of the nest can be a cup or part of a dome, depending on where it is built. It frequently has an outer layer of mud. The nest may be constructed in holes in the ground or in the trunks of trees, between the roots of trees, in hollows of dead trees, and sometimes within crevices in rocks. The bird lays three to four eggs that vary from pure white to pinkish white to bluish white, with lavender or reddish brown spots. The spots are more common on the larger end of the egg. Both sexes incubate the eggs. The species is thought to have two or three broods in a year. The species feeds on small invertebrates found in or around the water, including larvae and crustaceans. It forages at the edge of the water, and is described as "moving restlessly". It forages on and among rocks at the edges of the water as well as in mid-stream; it will occasionally enter the water as well. Though it generally forages by hopping in an agile manner among rocks, it also makes brief forays above the water to snatch food items from the surface. Its flight is described as similar to that of a large wagtail; quick and direct, and slightly undulating. …