Common hawk-cuckoo

The common hawk-cuckoo, often referred to as the brainfever bird, is a medium-sized cuckoo endemic to the Indian subcontinent. It closely resembles the Shikra in both appearance and flight. These birds are particularly notable for their unique breeding behavior as brood parasites, meaning they lay their eggs in the nests of other birds, specifically babblers.

During the breeding season, males are renowned for their distinctive calls that sound like "brain-fever" which is the source of one of their common names. They sport ashy grey plumage with brown crossbars, a prominent yellow ring around their eyes, and a broadly barred tail. In terms of diet, common hawk-cuckoos primarily consume insects, including hairy caterpillars. They have a specialized method of handling these caterpillars, removing the toxins before consumption.

Taxonomically, these birds belong to the genus Hierococcyx and are classified into two recognized subspecies. They are found across the Indian subcontinent, from Pakistan to Sri Lanka. Their preferred habitats include trees in gardens, groves, and forests.

As brood parasites, common hawk-cuckoos lay a single blue egg in the nests of babblers, particularly those of the Turdoides species. The unsuspecting babbler parents subsequently raise the cuckoo chick, often at the expense of their own eggs, which the young cuckoo may eject from the nest. Interestingly, eye-worms from the genus Oxyspirura have been discovered in the orbital cavities of these birds.