Indian Hawk Cuckoo

The common hawk-cuckoo (Hierococcyx varius), popularly known as the brainfever bird, is a medium-sized cuckoo resident in the Indian subcontinent. It bears a close resemblance to the Shikra, even in its style of flying and landing on a perch. The resemblance to hawks gives this group the generic name of hawk-cuckoo and like many other cuckoos these are brood parasites, laying their eggs in nests of babblers. During their breeding season in summer males produce loud, repetitive three note calls that are well-rendered as brain-fever, the second note being longer and higher pitched. These notes rise to a crescendo before ending abruptly and repeat after a few minutes; the calling may go on through the day, well after dusk and before dawn.

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. The tail is broadly barred. The sexes are alike. They have a distinctive yellow eye ring. Subadults have the breast streaked, similar to the immature shikra, and there are large brown chevron marks on the belly. At first glance they can be mistaken for a hawk. When flying they use a flap and glide style that resembles that of sparrowhawks (especially the shikra) and flying upwards and landing on a perch they shake their tails from side to side. Many small birds and squirrels raise the alarm just as they would in the presence of a hawk. The sexes are alike but males tend to be larger.

They can be confused with the large 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.

Immature with orange bill and indistinct eye-ring (Kolkata) During summer months, before the monsoons, the males are easily detected by their repeated calls but can be difficult to spot. The call is a loud screaming three-note call, repeated 5 or 6 times, rising in crescendo and ending abruptly. It is heard throughout the day and frequently during moonlit nights. The calls of females are a series of grating notes. Common hawk-cuckoos feed mainly on insects and are specialised feeders that can handle hairy caterpillars. Caterpillar guts often contain toxins and like many cuckoos they remove 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.