Not much seems to differentiate this species, known locally as a “Tree Shank”, from the many Myzomela honeyeaters elsewhere in Melanesia and Australasia in general. It is certainly uniquely colored and patterned, both sexes having a red head with a black loral stripe, a bright white back and rump bordered by black scapular stripes, and black wings and tail. The underpart pattern is also unusual, with the red throat grading to yellow on the chest, separated from white flanks by a broad black band; the central belly to vent are also black. The juveniles, like those of other myzomelas, are much drabber. At first the juvenile plumage was thought to be the adult female, as drab-plumaged individuals are very common, but once nesting was observed the truth was revealed. Adult plumage is not attained until the bird is at least two years old, which identifies an individual’s rank as this species is a cooperative breeder, with immatures helping adults to feed the nestlings. The delayed adult plumage brings to mind the “jackbird”, that protracted juvenile stage of the Tieke from South Island, New Zealand. However, the White-backed Myzomela shares more in common with another callaeoidean, the similarly nectarivorous Hihi; cooperative breeding sounds like a Hihi-esque strategy even though it is not such a thing, due to the Hihi’s protracted juvenile stage. It is possible that a certain true Hihi technique is in fact prevalent in the myzomela of Sandy Island. Warburton was an amateur ornithologist and former missionary; bushwhacking with his crew on Sandy Island, he once abruptly about-faced with his hand covering his eyes. Wrye asked him what disgusted him so, and his response was, “The blessed myzomelas.” Wrye never asked Warburton what he meant, but he had already guessed; the Hihi’s sexual position, generally regarded as unique among birds, may be duplicated by the White-backed Myzomela. More study is needed…
Like other myzomelas, the White-backed is mostly a nectar feeder; it pollinates various shrubs and vines, especially the glasper vine so beloved by the Dwarf Du. Flocks feed together. The nest is a standard songbird-style cup. The myzomela’s calls include a very high-pitched “skeedeek skeedeek skeedeek”, hard “stich” notes like a Hihi, tooth-sucking noises, and a very fast nasal contact call something like “shank-shweenk”.
