[9] More recently, DNA analysis has shown the family to be related to the honeyeaters (Meliphagidae) and the pardalotes (Pardalotidae) in a large superfamily Meliphagoidea.

In his 1982 monograph, ornithologist Richard Schodde proposed a northern origin for the chestnut-shouldered fairywren group due to the variety of forms in north and their absence in the southeast of the continent.

Ancestral birds spread south and colonised the southwest during a warm wetter period around 2 million years ago at the end of the Pliocene or beginning of the Pleistocene.

Further warmer, humid conditions again allowed birds to spread southwards, this group occupying central southern Australia east to the Eyre Peninsula became the blue-breasted fairywren.

Finally, after the end of the last glacial period 12,000–13,000 years ago, the northern variegated forms have again spread southwards, resulting in the purple-backed fairywren.

[citation needed] Like other fairywrens, it is notable for its marked sexual dimorphism, males adopting a highly visible breeding plumage of brilliant iridescent blue and chestnut contrasting with black and grey-brown.

[24] The blue plumage also reflects ultraviolet light strongly, and so may be even more prominent to other fairywrens, whose colour vision extends into that part of the spectrum.

[26] Some early evidence suggested subspecies assimilis may be nomadic, but later more detailed fieldwork indicated it was generally sedentary, with pairs of purple-backed fairywrens maintaining territories year-round.

[28] Fieldwork in the Northern Territory showed that the species preferred open woodland dominated by thickets of lancewood (Acacia shirleyi) and bullwaddy (Macropteranthes kekwickii) than eucalyptus.

[30] Clearing of native vegetation for agriculture in the Western Australian wheatbelt and Murray-Mallee region of Victoria had a negative impact on the species, as does the consumption of saltbush by cattle.

[27] Breeding can occur at any time in inland Australia, with birds taking the opportunity to nest after heavy rains, although only one brood is usually raised each year.

[28] The nest is a round or domed structure made of loosely woven grasses, twigs, bark and spider webs, with an entrance in one side, and is often larger than those of other fairywrens.