A medium-sized cuckoo resident in South Asia is the common hawk-cuckoo (Hierococcyx varius), Cuculus varius also popularly called the brainfever bird. Also in its manner of flying and landing on a perch, it bears a close resemblance to the Shikra. The similarity to hawks gives the common name of hawk-cuckoo to this group and like many other cuckoos, these are brood parasites, laying their eggs in babbler nests. In Punjab, Pakistan east, the Common Hawk-cuckoo occurs across most of the Indian peninsula from around 800 m south of the Himalayas; Bangladesh; Sri Lanka. It is usually native but is a local migratory where it occurs at high altitudes and in arid areas. In summer males make noisy, repeated three-note calls during their breeding season which are well-rendered as brain-fever, the second note being longer and higher pitched. These notes rise to a crescendo before ending abruptly and repeating after a couple of minutes; the call may continue through the day, long after dusk and before dawn. It’s habitat is dry deciduous forests, mostly occurring singly. Most birds don’t migrate, but altitudinal movements are known. Records in Oman and Thailand suggest some movement, possibly associated with the weather.
This species is common in forest lands, plantations, and gardens. Typically only under 1000 m, often up to 1500 m. The Common Hawk-cuckoo, around the size of a pigeon (approx. 34 cm), is a medium to the large cuckoo. The plumage above is ashy grey; whitish below, with brown, barred. Broadly barred tail; sexes alike. They mimic sparrowhawks (Shikra) when flying into trees and move their tails from side to side upon landing on the perch. Many little birds and squirrels raise the alarm in the presence of a hawk, just as they would. The genders are the same but the males appear to be taller. They can be confused with the big hawk-cuckoo, which, however, has dark streaks on the throat and breast. Young birds have a pale chin but young large hawk-cuckoos have a black chin. Like many other cuckoos, this species could be a brood parasite, preferring babblers. Its breeding season is from March to June, coinciding with that of babblers Turdoides and laughing thrushes Garrulax. In each nest is laid a single egg, blue, like the hosts. The hatchling evicts its host’s eggs and is reared by foster parents to maturity. The species is arboreal and never comes down to the ground. Its ecosystem is comprised of garden land, tree groves, deciduous and semi-evergreen forests. Feeds on insects, mainly caterpillars but also cutworms, grasshoppers, locusts, and others. It grows banyan and wild banana fruits. The brainfever bird’s call is also heard at some point of the day, starting early before dawn and regularly during moonlit nights. A unique by the Indian author Allan Sealy is called after this bird.