About Cacomantis variolosus (Vigors & Horsfield, 1827)
Cacomantis variolosus, commonly known as the Sahul brush cuckoo, measures approximately 22–26 cm (8.7–10.2 in) in total length. Adult males and females have nearly identical plumage. Adults have a pale grey head, buff breast, and grey-brown back. The underside of the tail is brown, marked with white tips and white bars. A narrow pale ring encircles the eye, and the feet are olive-pink. Juvenile plumage is heavily barred dark brown. In flight, the wings are sharply pointed and swept backward. The underwings are grey-brown, with pale buff underwing coverts and a white or pale buff bar. The Sahul brush cuckoo closely resembles the pallid cuckoo, and looks especially similar to the fan-tailed cuckoo and chestnut-breasted cuckoo. The Sahul brush cuckoo is distributed across northern and eastern Australia, New Guinea, the Solomon Islands, Malaysia, and other islands located north of Australia. It is a resident species in some parts of its range: Thailand, peninsular Malaysia, Cambodia, southern Vietnam, the Philippines, the Greater Sunda Islands, Lesser Sunda Islands, the Maluku Islands, and Timor. It engages in local migration in New Guinea and northern Melanesia. In Australia, the species is migratory in the southern portion of its range. In Australia, it occupies a variety of habitats including rainforests, rainforest edges, mangrove forests, secondary forests, and plantations. The Sahul brush cuckoo is an obligate brood parasite. Its eggs are polymorphic, with individual females laying specific egg types matched to specific host species. In Australia, females lay three distinct egg types, matching the major host species found in their local region of the species’ range. Across its entire Australian distribution, the Sahul brush cuckoo exploits at least 58 different avian species as hosts, though only a small number of these host species have been observed raising cuckoo chicks to the fledging stage. The host species that do raise chicks to fledging vary depending on the Sahul brush cuckoo subspecies. For the subspecies C. v. dumetorum, these confirmed foster hosts are the purple-crowned fairywren, brown-backed honeyeater, and bar-breasted honeyeater. For the subspecies C. v. variolosus, confirmed foster hosts are the rose robin, Norfolk robin, leaden flycatcher, restless flycatcher, satin flycatcher, rufous fantail, and grey fantail. In Indonesia, observed hosts for the local Sahul brush cuckoo subspecies include the grey-headed canary-flycatcher, Javan blue flycatcher, snowy-browed flycatcher, Sunda forktail, long-tailed shrike, striated grassbird, sooty-headed bulbul, yellow-vented bulbul, Malaysian pied fantail, rufous-tailed fantail, pied bush chat, Buru white-eye, and Sangkar white-eye.
