Purple-backed Fairywren

The purple-backed fairywren (Malurus assimilis) is a fairywren that is native to Australia. Described by Alfred John North in 1901, it has four recognised subspecies. In a species that exhibits sexual dimorphism, the brightly coloured breeding male has chestnut shoulders and azure crown and ear coverts, while non-breeding males, females and juveniles have predominantly grey-brown plumage, although females of two subspecies have mainly blue-grey plumage. Distributed over much of the Australian continent, the purple-backed fairywren is found in scrubland with plenty of vegetation providing dense cover.

The purple-backed fairywren is on average 14.5 cm long. 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. The brightly coloured crown and ear tufts are prominently featured in breeding displays. The male in breeding plumage has striking bright blue ear coverts and blue-purple crown and forehead, a black throat and nape, a blue-purple upper back, chestnut shoulders and a bluish-grey tail. The wings are drab brown and the belly white. Within subspecies assimilis, the plumage of both sexes is becomes paler from east to west across its range, with those of northwestern Australia paler still. Non-breeding males, females and juveniles of subspecies assimilis are predominantly grey-brown in colour, while those of subspecies rogersi and dulcis are mainly blue-grey. Males of all subspecies have a black bill and lores (eye-ring and bare skin between eyes and bill), while females of subspecies assimilis and rogersi have a red-brown bill and bright rufous lores, and those of subspecies dulcis have white lores. Immature males will develop black bills by six months of age, and moult into breeding plumage the first breeding season after hatching, though this may be incomplete with residual brownish plumage and may take another year or two to perfect. Both sexes moult in autumn after breeding, with males assuming an eclipse non-breeding plumage. They will moult again into nuptial plumage in winter or spring. The blue coloured plumage, particularly the ear-coverts, of the breeding males is highly iridescent due to the flattened and twisted surface of the barbules. 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.