For example, on Seram, members of the nominate subspecies variolosus join the local aeruginosus during the southern hemisphere winter.

[3] The convention of uniting the subspecies under C. variolosus dates back at least to Peters' checklist,[4] but there is uncertainty about whether they all belong there or not.

The head is pale grey, the breast is buff, the back is grey-brown, and the underside of the tail is brown with white tips and bars.

In Australia, females lay three types of egg depending on their major host in the relevant region of their distribution.

The species observed to raise chicks through fledging vary by subspecies of the Sahul brush cuckoo.

[12][11] In Indonesia, observed hosts of the local subspecies of Sahul brush cuckoo include the grey-headed canary-flycatcher,[13] Javan blue flycatcher,[13][14] snowy-browed flycatcher,[13] Sunda forktail,[13] long-tailed shrike,[13][15] striated grassbird,[13][15] sooty-headed bulbul,[13] yellow-vented bulbul,[13] Malaysian pied fantail,[13][14][15] rufous-tailed fantail,[13] pied bush chat,[13] Buru white-eye[16] and Sangkar white-eye.