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Common hawk-cuckoo or brainfever bird (Cuculus or Hierococcyx varius)The Common hawk-cuckoo is a medium to large-sized cuckoo, about the size of a pigeon (ca. 34 cm). The plumage is ashy grey above; whitish below, cross-barred with brown. There is a yellow eye-ring and the tail is broadly barred. The sexes are alike, but males tend to be larger (5). This species has evolved as a visual mimic(3) of the shikra sparrow hawk, even in its style of flying and landing on a perch. Subadults have the breast streaked, similar to the immature Shikra, and there are large brown chevron marks on the belly (4). The cuckoos fly using a flap and glide style like that of sparrowhawks. They fly upwards and land on a perch, where they shake their tails from side to side. Many small birds and squirrels raise the alarm as they would near a hawk. The sexes are alike but males tend to be larger (5). The common hawk-cuckoo can be confused with the large hawk-cuckoo, which has dark streaks on the throat and breast. Young birds have an orange bill, indistinct eye-ring and pale chin but young large hawk-cuckoos have a black chin (6).
The hawk-cuckoo lives in most of the Indian Subcontinent, from Pakistan, across the Himalayas foothills, east to Nepal, Bhutan and Bangladesh and south into Sri Lanka. Some birds of the Indian population winter in Sri Lanka. In the hills of central Sri Lanka, ciceliae is a resident. It is generally resident, but is locally migratory where it occurs at high altitudes and in arid areas. It is found in the lower elevations (mostly below 1000m) of the Himalayas but in higher areas, the large hawk-cuckoo tends to be more common (5). The common hawk-cuckoo's habitat includes garden land, groves of tree, deciduous and semi-evergreen forests (5).
The species is arboreal and rarely descends to the ground. It feeds mainly on insects and is a specialist that can handle hairy caterpillars. Caterpillar guts often contain toxins, so the cuckoo removes the guts by pressing the caterpillar and rubbing it on a branch before swallowing it. The hairs are swallowed with the caterpillar and are separated in the stomach and regurgitated as a pellet (6). Parasitic eye-worms (Oxyspirura) have been found in the orbital cavity of the species (15).
The breeding season is March to June, coinciding with that of some of Turdoides babblers and before the monsoons. Males produce loud, screaming three note calls, the second note being longer and higher pitched. The notes rise to a crescendo before ending abruptly and repeated 5-6 times after a few minutes; the calling may go on through the day, well after dusk, on moonlit nights and before dawn (7), hence 'brain-fever bird'. The calls of females are a series of grating notes (5). The female is a brood parasite, laying its eggs in nests of babblers, mainly in the genus Turdoides (possibly the only host (4)) and also reportedly on laughing-thrushes (Garrulax) (10). The female lays one egg in each nest; the eggs is blue, like that of the host. The hatchling usually evicts the eggs of its host and is reared to maturity by foster parents, following them for nearly a month (6). T C Jerdon said it may not always evict the host and that young birds may be seen with young babblers (11). When the chick moves with a flock of babblers, it makes a grating kee-kee call to beg for food and the foster parents within the group may feed it (5) The predominant host species in India are Turdoides striatus and T. affinis (12). Hawk-cuckoos also parasitise the large grey babbler (T. malcolmi) (7,13) In Sri Lanka, their host is T. striatus (14).
The cuckoo is rated as Least Concern, due to its extremely large range and its seeming stable population. The population size is not believed to approach the thresholds for Vulnerable. The species is reported to be common in most parts of its range but is rarer in Sri Lanka (18)
The type locality of the species is Tranquebar in Tamil Nadu; Martin Hendriksen Vahl described the species in 1797 (8). This species is placed under the genus Hierococcyx, which includes other hawk-cuckoos, but is sometimes included in the genus Cuculus (4). The two subspecies are varius from India and ciceliae of the hill regions of Sri Lanka (9). The Indian population has paler plumage than ciceliae (4).
The call of this bird has been transcribed as brain-fever in English (in some old books, this name is also incorrectly used for the Asian Koel). Frank Finn noted the "damnable iteration" of a piercing voice running up the scale (16). Other interpretations of the bird call include peea kahan in Hindi ("where's my love") or chokh gelo (in Bengali, "my eyes are gone") and paos ala (Marathi, "the rains are coming"). The call "Pee kahan" or "Papeeha" is more accurately represented by the shrill screaming "pi-peeah" of the large Hawk-Cuckoo (Hierococcyx sparverioides), which replaces the Brainfever Bird along the Himalayas and its foothills (6). A novel by the Indian author Allan Sealy is named after this bird (17).