As we wait in post-C&B limbo to discover which body will replace Christidis & Boles  as the official arbiters of the Australian list, it appears almost certain that the next revision – by whoever – will split the western form of the White-naped Honeyeater (Melithreptus lunatus) as M. chloropsis. This change has already been adopted by the influential IOC World Bird List from v2.6 (Oct 23 2010)  and restores the species described and named by Gould himself in 1848 .
Both Gould and modern taxonomists cite the western form’s larger size, longer and thicker bill, thicker black margin around chin, and different colouration of the bare skin above the eye, which is bright red in lunatus but white to very pale blue-green in chloropsis (Latin for green-eyed). In support of re-splitting the species, a recent molecular analysis by Toon et al. (2010)  has demonstrated the two are paraphyletic, meaning that M. lunatus is more closely related to another species (the Black-headed Honeyeater M. affinis of Tasmania) than it is to its previously-alleged subspecies M. l. chloropsis. [Incidentally, Toon et al. found surprisingly “shallow” genetic differences in M. brevirostris, so I don’t think we’ll be seeing the elevation to species of Western Brown-headed Honeyeater leucogenys any time soon].
|A Western White-naped Honeyeater, Melithreptus chloropsis, from marginal jarrah/karri forest at Donnelly River (near Bridgetown).|