Purple-crowned Fairywren

Like all other species in the genus Malurus, the purple-crowned fairywren 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 fairywrens 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.

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 1,500 km (930 mi), it is constrained by the quality and extent of riparian vegetation along waterways. A natural geographic barrier of approximately 300 km (190 mi) of unsuitable habitat separates the two subspecies. The western subspecies M. c. coronatus occurs in the midsections 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-western and southern Gulf of Carpentaria from Roper River in Northern Territory to Leichhardt and Flinders Rivers in Queensland. The purple-crowned fairywren 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 (i.e. Pandanus aquaticus and/or a freshwater mangrove, Barringtonia acutangula), as seen in the Kimberley region or areas of 1.5–2 m (4 ft 11 in–6 ft 7 in) 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.

The purple-crowned fairywren 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 subspecies meets the criteria for being listed as Endangered while the eastern subspecies meets criteria for Near Threatened. The population size for M. c. macgillivrayi may be close to 10,000 mature individuals in a single subpopulation, while recent surveys of M. c. coronatus estimate that the overall population size is possibly as low as 10,000, given the extent of available habitat. The species has suffered severe declines in population. It now only occurs on a subset of the waterways where they were previously found. Specifically, three substantial declines are recorded. The species disappeared from the lower Fitzroy River around the 1920s with the introduction of sheep and cattle grazing, and subsequent replacement of native riparian vegetation by weeds. They disappeared from a large section of the Ord River following construction of the Ord River Dam and subsequent flooding of the area. Finally, a more recent study in the Victoria River region reported ongoing population decline in response to intensive cattle grazing of river frontages. The distribution of M. c. coronatus has been severely reduced since the subspecies was first discovered 140 years ago. The western subspecies now only occurs on limited stretches of six river systems: the upper Fitzroy, Durack, Drysdale, Isdell catchments, the northern Pentecost, and Victoria River. Declines in other areas are likely because of the deterioration in the condition of riparian zones.