[5] The species epithet penicillata derives from the Latin word penicillis meaning 'brush tip', referring to the white plume across the side of the neck.

[8] This had first been suggested by Mathews in 1915, who placed it with the Yellow-tinted honeyeater in a genus he named Ptilotula;[9] but this was rejected by the Royal Australasian Ornithologists Union.

[12] The species is probably of Miocene origin, with a fossil fragment found in Riversleigh, Queensland, appearing very similar to the white-plumed honeyeater leg-bone.

[6] Upperwing coverts are mostly brown with olive to yellow-olive tips or edges, creating a somewhat scalloped appearance.

Remiges are dark brown with yellowish edges to secondaries, forming a yellow-olive panel when the wing is folded.

The bill is pink or yellowish with a brown tip in young individuals, changing to black with a yellow-orange or pinkish base; while the gape is yellow and noticeably puffy looking.

In newly fledged birds, the feet and legs are a paler pinkish-brown and appear swollen compared to the adult.

[6] They are absent from desert areas but can persist in arid regions where trees and especially standing water are present.

[6][14] It was formerly linked closely to the distribution of river red gum (Eucalyptus camaldulensis) and a few other riverine species;[15] but it has since expanded into coastal areas to become resident in Sydney and Newcastle, where they were previously uncommon or only seasonal visitors.

An oligotypic species,[16] it is mainly found in open sclerophyll woodland, often near water sources, such as wetlands, swamps, creeks, and dams.

[6][17][18][19] The white-plumed honeyeater's diet consists mainly of nectar, insects and their products (e.g., honeydew and lerp), manna, fruit, and very occasionally seeds.

[26] A study in the Pilbara region of Western Australia found that white-plumed honeyeaters must eat around 100 berries to obtain 1mL of water.

Needing 5-10mL per day, white-plumed honeyeaters were able to feed on 500–1000 berries in a five-hour period in order to obtain both caloric requirements and sufficient water intake.

[30] Insects are sometimes taken on the wing, but probably only provide a protein and mineral source, as a surplus of energy is available in nectar, lerp, and manna.

[17] In some regions, smaller birds are absent, due to the aggressive nature of white-plumed honeyeaters and other species of similar size, resulting in the exclusion of these poorer competitors.

[6] Corroborees of up to 12 or more individuals, sitting together on a branch, have been observed, which engage in extensive calling, followed by rapid dispersal.

[citation needed] Females are relatively more ready to breed from late winter through to summer;[33] however, males maintain enlarged testes throughout the year.

[34] Breeding occurs throughout their range with records in all months, and clutches typically produced 2–3 times per year.

[6] These are skillfully woven from grasses and fine bark strips, bound with spider webs, and lined with animal hair, wool, and feathers.

Colour varies from white to pale buff or deep pink, minutely spotted with chestnut-red freckles towards the larger end.

[1] Exotic vertebrate predators, such as cats and dogs, are a direct threat to white-plumed honeyeater populations.

[6] Loss of trees from watercourses will impact a population; however, they are able to adapt to suburban environments, especially where native gardens are present.