Hylocitreidae – Yellow-flanked Whistler

The Hylocitredidae are a family of just one genus with a sole species – Hylocitrea Hylocitrea bonensis, also known as the Yellow-flanked Whistler or Olive-flanked Whistler.

It is a passerine species that is endemic to montane forests on the Indonesian island of Sulawesi. It has one sub-species, Hylocitrea bonensis bonthaina that has some plumage differences but further research is needed to establish whether that is a mere morph, or, indeed a species in its own right.

The Hylocitrea has traditionally been considered a member of the family Pachycephalidae, but recent genetic evidence demonstrated the need for it to be placed in its own family, Hylocitreidae, although some ornithologists felt it should be treated as a monotypic subfamily of the family Bombycillidae. DNA sequencing demonstrated that it is not related to other whistlers and is actually closer to the Waxwings but never-the-less, forms a family all by itself.

Hylocitrea Hylocitrea bonensis – Andy Walker

It is a drab-coloured, whistler-like passerine. Mostly dull green with red eyes, a breast and belly, with yellowish flanks, and a rusty base to the undertail. Females show throat streaking that is absent in males; the streaks are white in the southwest and yellowish in the northern nominate subspecies. Juveniles have an olive-brown head and buff-striped olive underparts.

Singles and pairs occupy the subcanopy of montane forest. It can be separated from female Maroon-backed Whistler by its yellow flanks, red eye, slim pointed bill, and tendency to sit high in the trees. Calls include a high-pitched thrush-like “tsip” and a nasal “jheeze.” Song comprises very high-pitched, twittering whistles.

Nothing is known of its breeding habits etc.