Purple-crowned fairywren

Appearance

The purple-crowned fairy-wren is a sexually dimorphic small bird measuring approximately 14 cm in length, with a wing-span of approximately 16 cm and weighing 9−13 g. The plumage is brown overall, the wings more greyish brown, and the belly cream-buff. The blue tail is long and upright, and all except the central pair of feathers are broadly tipped with white. Their bill is black and the legs and feet are brownish grey. Although there is slight geographical variation between the two subspecies, only the difference in colour of mantle is noticeable in the field. The crown and nape of ''M. c. macgillivrayi'' is slightly bluer, and its mantle and upper back has weak blue grey shading, whereas the slightly larger ''M. c. coronatus'' has a browner back, as well as a buff-coloured, rather than white, breast and belly.
During the breeding season adult males develop the spectacular bright purple feathers on their crown, this is bordered by a black face mask and capped with a black oblong black spot on top of the head. During the non-breeding season adult males replace their colourful crown with grey/brown feathers and reduce their black mask to black cheek patches, and an off-white to pale grey orbital ring. The adult female differs in having a blue-tinged grey crown, chestnut ear-coverts, and greenish blue tail. Immature birds are very similar to adult females except for a duller coloration, a brown crown, and longer tail, though male birds start to show black feathers on the face by 6 to 9 months

Naming

Predation by invasive species such as feral cats and black rats is also a threat as degradation of the under-storey causes a reduction of shelter exposing birds to predation. Populations of ''M. c. coronatus'' decreased by 50% over a two-year period at two sites in the Victoria River District where grazing and trampling was allowed around habitat patches. Very low breeding success from nest predation was attributed to black rats at one site.

Distribution

The species occurs across the wet-dry tropics of northern Australia, and is found in the Kimberley region of Western Australia, in the Victoria River region of the Northern Territory, and in the south-western sub-coastal region of the Gulf of Carpentaria in Queensland. Whilst the species’ distribution spans more than 1500 km, it is constrained by the quality and extent of riparian vegetation along waterways. A natural geographic barrier of approximately 300 km of unsuitable habitat separates the two subspecies. The western subspecies ''M. c. coronatus'' occurs in the mid-sections of large river catchments that drain the Central Kimberley Plateau, and along sections of the Victoria River. The eastern subspecies ''M. c. macgillivrayi'' occurs along most rivers draining into south-west and south Gulf of Carpentaria from Roper River in Northern Territory to Leichhardt and Flinders River in Queensland.

Status

The purple-crowned fairy-wren is currently classified as Least Concern by the IUCN. However, the two recognised subspecies receive separate national conservation management listings. In 2015, the Australian Federal Government upgraded the conservation status of the western subspecies from Vulnerable to Endangered. According to the IUCN Red List, the western race meets the criteria for being listed as Endangered while the eastern race meets criteria for Near Threatened.The protection of riparian vegetation needs to be a priority for managers of all land tenures to ensure their persistence. Active conservation is more urgent for the Endangered ''M. c. coronatus'', as only 17% of its habitat occurs in conservation reserves in the Kimberley Region. Small populations on the northern Pentecost and Isdell Rivers are at highest risk of extinction, and urgently need a fine-scale targeted approach to help conserve them. A strategy that maintains connectivity across the species distribution and reduces continuing riparian degradation needs to be implemented. Suggested management actions needed at key sites are controlling access of stock and feral herbivores to riparian areas and excluding livestock from riparian zones; reducing the incidence of intense fires that affect fire-sensitive riparian vegetation by implementing improved fire-regimes; controlling the spread of weeds ; preservation of quality riparian habitat ; and restoring riparian habitat, especially in areas of high risk.The Department of Agriculture and Food Western Australia joined with Wungurr Rangers and pastoralists in the north-west Kimberley in an effort to protect parts of their habitat by removing Ornamental rubbervine . The Australian Wildlife Conservancy is protecting riparian vegetation on its Mornington-Marion Downs, and Pungalina-Seven Emu sanctuaries by implementing a program of fire management and introduced herbivore control. EcoFire, an award-winning landscape-scale fire management program of the central and north Kimberley including indigenous communities and pastoralists, helps protect the fire-sensitive vegetation crucial for the survival of the purple-crowned fairy-wren.

Behavior

Like all other ''Malurus'', the purple-crowned fairy-wren is a cooperative breeder and lives in sedentary groups that maintain their territories, often arranged linearly along creeks and rivers, year-round. However unlike other species in the genus that are highly promiscuous, purple-crowned fairy-wrens display high levels of fidelity and low rates of extra-pair paternity. Groups generally consist of a breeding pair that is helped by one to six offspring from previous broods, and helpers may stay with their parents for several years before attempting to breed. Only the dominant pair in a group reproduces, and individuals can remain un-reproductive subordinates for several years. These subordinates help raise the offspring, improving productivity as well as the survival of the breeding pair.

Habitat

The purple-crowned fairy-wren is a riparian habitat specialist that occurs in patches of dense river-fringing vegetation in northern Australia. Its preferred habitat, which lines the permanent freshwater creeks and rivers, consists of a well-developed mid-storey that is composed of dense shrubs , as seen in the Kimberley region or areas of tall dense thickets of river grass dominated by ''Chionachne cyanthopoda'' as seen in the Victoria River District. A tall dense canopy of emergent trees, used as a temporary refuge during flooding events that submerge the mid-storey, is often dominated by ''Eucalyptus camaldulensis'', ''Melaleuca leucadendra'', ''Melaleuca argentea'' and ''Ficus spp''.Like all other ''Malurus'', the purple-crowned fairy-wren is a cooperative breeder and lives in sedentary groups that maintain their territories, often arranged linearly along creeks and rivers, year-round. However unlike other species in the genus that are highly promiscuous, purple-crowned fairy-wrens display high levels of fidelity and low rates of extra-pair paternity. Groups generally consist of a breeding pair that is helped by one to six offspring from previous broods, and helpers may stay with their parents for several years before attempting to breed. Only the dominant pair in a group reproduces, and individuals can remain un-reproductive subordinates for several years. These subordinates help raise the offspring, improving productivity as well as the survival of the breeding pair.

Reproduction

Breeding can occur at any time throughout the year, if conditions are suitable, with peaks in the early and late dry season. Nesting has primarily been recorded close to the ground in thickets of river grass ''C. cyanthopoda'' and ''P. aquaticus''. Only the females build the small dome shaped nests constructed mainly of fine rootlets, grass, leaves and strips of bark. Pairs may produce up to 3 broods per year. A clutch containing 2-3 eggs is laid over successive days, and is incubated by only females for 14 days, and chicks fledge after 10 days. Fledglings are unable to fly and stay in dense cover for a week and are fed by members of the family group for at least another 3 weeks.Incestuous matings by ''M. coronatus'' result in severe fitness costs due to inbreeding depression . Females paired with related males may undertake extra pair matings that can reduce the negative effects of inbreeding . Although there are ecological and demographic constraints on extra pair matings, 43% of broods produced by incestuously paired females contained extra pair young. In general, inbreeding is avoided because it leads to a reduction in progeny fitness largely due to the homozygous expression of deleterious recessive alleles.

Food

The species is mainly insectivorous. Birds consume a range of small invertebrates such as beetles, ants, bugs, wasps, grasshoppers, moths, larvae, and spiders, and small quantities of seeds. They forage for their prey in amongst foliage and in the leaf litter on the ground that may have accumulated as debris during floods. Group members will forage separately, hopping rapidly through the dense undergrowth, but remain in contact with each other by making soft ‘chet’ sounding calls.

Predators

Given the spatial arrangement of small populations in patchily distributed habitat across northern Australia, the species is potentially vulnerable to decline from loss of fairly small areas of habitat. The purple-crowned fairy-wren's greatest threat is degradation or loss of habitat from introduced herbivores, weeds, fire, flooding and mining. Introduced herbivores seeking water eat and trample riparian vegetation that purple-crowned fairy-wrens rely on for foraging, nesting and shelter. More frequent and/or more intense fires are detrimental as they can modify both the extent and structure of riparian vegetation. Interactions between climate change and habitat degradation are also likely, with the negative impacts of floods likely to be worse for populations living in degraded habitat.