Adults of the species exhibit sexual dimorphism with the females duller overall; juveniles lack the striking colours of mature birds and the characteristic patterning is not as easily distinguished.

Individuals form mating pairs and generally remain in one locality, although they will venture out to join small groups at plentiful sources of food.

The population is classified as two subspecies, representing an inland group residing in the agricultural district and another nearer the coast in kwongan, tall forest and a variety of woodlands.

The first description of the species was published by C. J. Temminck and Heinrich Kuhl in 1820 as Psittacus icterotis,[2] using a collection obtained at King George Sound (Albany, Western Australia).

Mathews notes Salvadori's separation of the type specimen from two others in the Gould collection, then held at the London museum, and caution in only giving the source of the skin as "unknown, but probably Australia".

In the preface to the same volume, Mathews attributes the material examined from the southwest of Australia to the collections of the botanist Robert Brown on the Flinders expedition.

[14] The epithet whitlocki was used by authors in ornithological literature to honour the Western Australian field research of Frederick Lawson Whitlock.

[15] The notes of Whitlock and other authors reporting from Western Australia, including Tom Carter and A. W. Milligan, were assembled or quoted by Mathews.

[7] The description of the population as two or three subspecific taxa by Mathews is cited within the species circumscription, his P. icterus whitlocki, along with Salvadori's P. xanthogenys, are noted as synonyms for the inland subspecies.

[8] The platycercine parrots have seen various systematic arrangements to circumscribe the contentious sister taxa of northern and eastern Australia, most of which overlap in range and intergrade.

[17][16] The validity of the alliances in the subgeneric arrangement, especially of Platycercus (Violania), was tested in 2015, with a multilocus approach to phylogenetic analysis, and proposed a hypothesis that challenges the relationships within the genus.

The pre-existing names, derived from the Nyungar language, were recorded as regional and literal variants, representing dialectic shifts and often inconsistent spelling by the transcriber.

[32] Immature birds resemble the adult female though with even more green plumage, red only on the crown, and lacking a yellow cheek patch entirely.

[37][39] Gould (1848) reported the whistling of the notes as a feeble, piping sound and the rich variation in the series might be regarded "as almost to assume the character of a song".

The line of demarcation between the inland and coastal subspecies begins east of King George Sound and lies to the northwest via Mount Barker and the Kojonup region toward the Bannister River.

The adaptation to introduced agricultural crops has been comparatively limited when contrasted with the range of seeds harvested by ringnecks Barnardius zonarius and others species.

[44] The erroneous locations reported by Mathews, Point Cloates and Shark Bay, were later admitted to have been incorrect by the author; he also identifies the obvious error in Gould's protologue (1837) in extending the range from King George Sound to "… New South Wales.

[37] This subspecies feeds at seeding wandoo, Acacia huegeliana, Glischrocaryon flavescens and Olearia revoluta and flowering Eucalyptus eremophila and Melaleuca acuminata.

[38] The western rosella usually socialises in pairs, but congregates in groups of twenty or so to forage when the season or opportunity permits; numbers in a flock are occasionally recorded up to twenty-six.

[40][38] The birds are discreet in their behaviours—more so than other rosellas—and will remain unobserved when feeding on the ground beneath the understory of a woodland or sheltering during the day in the dense foliage of trees.

[34] The group in a study at Wickepin and Dudinin (Kulin Shire) was observed to begin occupancy of nest sites in July, the routine of the female being fed by the male being established in the week before laying the brood.

[37] The western rosella nests in hollows and spout-shaped holes of living and dead trees, generally eucalypts and most commonly karri and wandoo.

[20] The dimensional description of the nest site, relating height, depth and entrance size used by the species, was included in a study of animals occupying tree cavities in jarrah forest, and intended to assist in determining the amount of suitable habitat removed and remaining after logging.

[40] The male remains close to the site, feeding at ground level and moving to an upper branch to call when catering to the brooding female.

[37] The diet consists primarily of seeds, often those of introduced weeds and crops, although typically from eucalypt, sheoak and other native plants of the wooded environment.

[20] The habit of visiting colonial farmland for seed and soft fruit, and lack of concern at human presence, was first reported by Gould in the years immediately following the region's settlement by the English.

[37] In the assessment of the inland P. icterotis xanthogenys for the federal government's Action Plan for Australian Birds 2000 it was assigned the status of 'near threatened'.

[50] P. icterotis was used in a comparative study of tolerance in some Australian birds to sodium fluoroacetate, a highly toxic substance that occurs in plants of the southwest and commercially branded as "1080", to evaluate their sensitivity against the exposure and mobility of other species.

[51] Western rosellas are a popular bird in aviaries and for zoological gardens, displaying the favourable characteristics of related species without the reputation for aggression and raucous vocalisation.

[53] Sexing individuals by comparison of the colouring does not present the difficulties found in other captive rosellas, being markedly sexually dimorphic they are easily assigned.