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Species Guide
A photo of a Common Hawk-Cuckoo (Hierococcyx varius)
Common Hawk-Cuckoo

Common Hawk-Cuckoo

Hierococcyx varius

The common hawk-cuckoo, known colloquially as the brainfever bird, is a medium-sized cuckoo roughly the size of a pigeon, measuring approximately 34 cm in length. Its plumage is a muted ashy grey on top, with a paler underside marked by brown cross-bars. The tail is conspicuously barred. Both sexes exhibit a distinctive yellow eye ring, and while they appear similar, males are generally larger.

Identification Tips

Upon first glance, one might easily mistake the common hawk-cuckoo for a hawk due to its striking resemblance to the Shikra, particularly in flight behavior and landing. Subadults display streaked breasts akin to immature Shikras and bear large brown chevron marks on their bellies. The large hawk-cuckoo could be confused with this species, but it can be distinguished by dark streaks on its throat and breast, and young large hawk-cuckoos have a black chin, as opposed to the pale chin of the common hawk-cuckoo's young.


The common hawk-cuckoo favors arboreal habitats, seldom descending to the ground. It thrives in gardens, tree groves, and both deciduous and semi-evergreen forests.


This species is widespread across the Indian subcontinent, from Pakistan to the Himalayan foothills, and extends eastward to Nepal, Bhutan, Bangladesh, and Northeast India, reaching south into Sri Lanka. Some Indian populations migrate to Sri Lanka in the winter, while the subspecies in central Sri Lanka's hills is resident.


The common hawk-cuckoo is a brood parasite, laying its eggs in the nests of babblers, particularly those in the genus Turdoides. The breeding season aligns with that of its host species, from March to June. The hatchling often evicts the host's eggs and is raised by the foster parents, following them for nearly a month.

Song & Calls

The male's call is a loud, repetitive three-note sound, reminiscent of the phrase "brain-fever," with the second note being longer and higher pitched. These calls, which can continue throughout the day and into moonlit nights, rise to a crescendo before ending abruptly. The female's call consists of a series of grating notes.


During the breeding season, the common hawk-cuckoo lays a single blue egg, mimicking the appearance of the host's eggs. The chick may evict the host's eggs and is reared to maturity by the foster parents.

Diet and Feeding

The common hawk-cuckoo primarily feeds on insects, specializing in hairy caterpillars. It has developed a method to remove the caterpillar's guts, which often contain toxins, by pressing and rubbing the caterpillar on a branch before consumption. The ingested hairs are later regurgitated as a pellet.

Conservation status

The IUCN Red List has classified the common hawk-cuckoo as Least Concern, indicating that it currently faces no significant threat of extinction.

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