Appearance
Measuring 11–13.5 cm in length, White-winged Fairywrens are one of the two smallest species of ''Malurus''. Males typically weigh between 7.2 g and 10.9 g while females weigh between 6.8 g and 11 g . Averaging 8.5 mm in males and 8.4 mm in females, the bill is relatively long, narrow and pointed and wider at the base. Wider than it is deep, the bill is similar in shape to those of other birds that feed by probing for or picking insects off their environs. It is finer and more pointed in this species than in other fairywrens.Fully mature adults are sexually dimorphic, with the male being larger and differing in colour from the female. The adult female is sandy-brown with a very light blue tail, and a pinkish buff bill. The male in breeding plumage has a black bill, white wings and shoulders, and a wholly cobalt blue or black body . These contrasting white feathers are especially highlighted in flight and ground displays in breeding season. The male in eclipse plumage resembles the female, though it may be distinguished by its darker bill. Both sexes have long, slender, distinct tails held at an upward angle from their bodies. Measuring around 6.25 cm , the tail feathers have a white fringe, which disappears with wear.
Nestlings, fledglings, and juveniles have brown plumage and pink-brown bills with shorter tails than adults. Young males develop blue tail feathers and darker bills by late summer or autumn , while young females develop light blue tails. By the subsequent spring, all males are fertile and have developed cloacal protuberances, which store sperm. In contrast, during the breeding season, fertile females develop oedematous brood patches, which are bare areas on their bellies.
Males entering their second or third year may develop spotty blue and white plumage during the breeding season. By their fourth year, males have assumed their nuptial plumage, where the scapulars, secondary wing coverts, and secondary flight feathers are white while the rest of their bodies are a vibrant cobalt blue. All sexually mature males moult twice a year, once before the breeding season in winter or spring, and again afterwards in autumn; rarely, a male may moult directly from nuptial to nuptial plumage. The breeding males' blue plumage, particularly the ear-coverts, 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 this part of the spectrum.
Naming
There are three recognised subspecies of ''Malurus leucopterus''. Both black-plumaged forms have been called Black-and-white Fairywren.⤷ ''M. l. leuconotus'' is endemic to mainland Australia and distinct in that it is the only subspecies to have nuptial males that show prominent blue-and-white plumage. The name of this species is derived from the Ancient Greek ''leukos'' 'white' and ''notos'' 'back'. Birds in the southern parts of its range tend to be smaller than those in the north.
⤷ ''M. l. leucopterus'' is restricted to Dirk Hartog Island, off the western coast of Australia, and nuptial males display black-and-white plumage. This subspecies is the smallest of the three and bears a proportionally longer tail. It was collected again in 1916 by Tom Carter, 98 years after de Freycinet's expedition collected the type specimen.
⤷ ''M. l. edouardi'', like ''M. l. leucopterus'', have black-and-white coloured males, and are found only on Barrow Island, also off the western coast of Australia. Birds of this subspecies are larger than those of ''M. l. leucopterus'' but have a shorter tail. The female has a more cinnamon tinge to her plumage than the grey-brown of the other two subspecies. It was described by A.J. Campbell in 1901.
''M. l. leucopterus'' and ''M. l. edouardi'' are both generally smaller than their mainland relatives, and both subspecies tend to have smaller family groups that consist of only one male and one female, with an occasional helper bird. While the island subspecies and mainland species have been found to have similar social structure, breeding pairs on both islands have, on average, smaller clutches, longer incubation times, and fewer live fledglings. Additionally, while ''M. l. leuconotus'' is considered of Least Concern by the IUCN due to its widespread occurrence, both island subspecies are considered vulnerable by the Australian government due to their delicate nesting sites that are easily disturbed by human construction and habitation.
Distribution
The White-winged Fairywren is well adapted to dry environments, and ''M.l. leuconotus'' is found throughout arid and semi-arid environments between latitudes 19 and 32oS in mainland Australia. It occupies coastal Western Australia from around Port Hedland south to Perth, and stretches eastwards over to Mount Isa in Queensland, and along the western parts of the Great Dividing Range through central Queensland and central western New South Wales, into the northwestern corner of Victoria and the Eyre Peninsula and across the Nullarbor. It commonly cohabits with other species of fairywren, including the Purple-backed Fairy-wren . White-winged Fairywrens often inhabit heathlands or treeless shrublands dominated by saltbush and small shrubs of the genus ''Maireana'', or grasses such as tussock grass and cane-grass , as well as floodplain areas vegetated with lignum . ''M. l. leucopterus'' inhabits similar habitats on Dirk Hartog Island and ''M. l. edouardi'' does the same on Barrow Island. The White-winged Fairywren is replaced to the north of its range on mainland Australia by the Red-backed Fairywren.Behavior
The usual form of locomotion is hopping, with both feet leaving the ground and landing simultaneously. However, birds may run when performing the ''rodent-run'' display. Its balance is assisted by a proportionally large tail, which is usually held upright and rarely still. The short, rounded wings provide good initial lift and are useful for short flights, though not for extended jaunts.White-winged Fairywrens live in complex social groups. Clans consist of 2–4 birds, typically one brown or partially blue male and a breeding female. Nest helpers are birds raised in previous years which remain with the family group after fledging and assist in raising young; they may be male that have retained their brown plumage, or female. Birds in a group roost side-by-side in dense cover and engage in mutual preening. Several subgroups live within one territory and make up a clan, which is presided over by one blue male who assumes breeding plumage. While the blue male is dominant to the rest of the brown and partially blue males within his clan, he nests with only one female and contributes to the raising of only her young. It is unclear whether or not he fathers young in any of the other nests within his territory.
Each clan has a specified area of land that all members contribute to foraging from and defending. Frequently, territory sizes, normally 4–6 ha , are correlated with the abundance of rain and resources in a region; smaller territories occur where insects and resources are plentiful. Additionally, the feeding territories are larger during the winter months when these birds spend much of their time foraging with the entire clan. White-winged Fairywrens occupy much larger territories than other fairywren species.
Observed in this species, the ''wing-fluttering'' display is seen in several situations: females responding, and presumably acquiescing, to male courtship displays, juveniles begging for food, by helpers to older birds, and immature males to senior ones. The fairywren lowers its head and tail, outstretches and quivers its wings and holds its beak open silently.
Both the male and female adult White-winged Fairywren may utilise a ''rodent-run'' display to distract predators from nests with young birds. The head, neck and tail are lowered, the wings are held out and the feathers are fluffed as the bird runs rapidly and voices a continuous alarm call.
Habitat
The White-winged Fairywren is well adapted to dry environments, and ''M.l. leuconotus'' is found throughout arid and semi-arid environments between latitudes 19 and 32oS in mainland Australia. It occupies coastal Western Australia from around Port Hedland south to Perth, and stretches eastwards over to Mount Isa in Queensland, and along the western parts of the Great Dividing Range through central Queensland and central western New South Wales, into the northwestern corner of Victoria and the Eyre Peninsula and across the Nullarbor. It commonly cohabits with other species of fairywren, including the Purple-backed Fairy-wren . White-winged Fairywrens often inhabit heathlands or treeless shrublands dominated by saltbush and small shrubs of the genus ''Maireana'', or grasses such as tussock grass and cane-grass , as well as floodplain areas vegetated with lignum . ''M. l. leucopterus'' inhabits similar habitats on Dirk Hartog Island and ''M. l. edouardi'' does the same on Barrow Island. The White-winged Fairywren is replaced to the north of its range on mainland Australia by the Red-backed Fairywren.Reproduction
Fairywrens exhibit one of the highest incidences of extra-pair mating, and many broods are brought up a by male who is not the natural father. However, courtship methods among White-winged Fairywrens remain unclear. Blue-plumaged males have been seen outside of their territory and in some cases, carrying pink or purple petals, which among other species advertise the male to neighboring females. In contrast, black-plumaged males on Barrow and Dirk Hartog islands often carry blue petals. While petal-carrying outside of clan territories strongly suggests mating with other females is occurring, further genetic analysis is necessary.During another courtship display the male bows deeply forward facing the female, reaching the ground with his bill and spreading and flattening his plumage in a near-horizontal plane for up to 20 seconds. In this pose, the white plumage forms a striking white band across his darker plumage.
Breeding females begin to build their nests in the spring and construct domed structures composed of spiderwebs, fine grasses, thistle-down, and vegetable-down, typically 6–14 cm tall and 3–9 mm thick. Each nest has a small entrance on one side and they are normally placed in thick shrubs close to the ground. A clutch of 3–4 eggs is generally laid anywhere from September to January, with incubation lasting around 14 days. The White-winged Fairywren generally breeds in the spring in the southwest of Western Australia, but is more opportunistic in arid regions of central and northern Australia, with breeding recorded almost any month after a period of rainfall. Incubation is by the breeding female alone, while the breeding male and nest helpers aid in feeding the nestlings and removing their fecal sacs. The newly hatched nestlings are altricial, gaping immediately for food, and developing downy feather tracts and opening their eyes by the third or fourth day. Nestlings remain in the nest for 10–11 days, and fledglings continue to be fed for 3–4 weeks following their departure from the nest. Fledglings then either stay on to help raise the next brood or move to a nearby territory. It is not unusual for a pair bond to hatch and raise two broods in one breeding season, and helpers tend to lessen the stress on the breeding female rather than increase the overall number of feedings. Like other fairywrens, the White-winged Fairywren is particularly prone to parasitic nesting by the Horsfield's Bronze Cuckoo . Parasitism by the Shining Bronze Cuckoo and Black-eared Cuckoo is rarely recorded.
Food
The White-winged Fairywren is primarily insectivorous; its diet includes small beetles, bugs, moths, praying mantises, caterpillars, and smaller insects, including spiders. The larger insects are typically fed to nestlings by the breeding female and her helpers, including the breeding male. Adults and juveniles forage by hopping along the shrubland floor, and may supplement their diets with seeds and fruits of saltbush , goosefoot and new shoots of samphire. During spring and summer, birds are active in bursts through the day and accompany their foraging with song. Insects are numerous and easy to catch, which allows the birds to rest between forays. The group often shelters and rests together during the heat of the day. Food is harder to find during winter and they are required to spend the day foraging continuously.Predators
Adults and their young may be preyed upon by mammalian predators, such as the red fox or the feral cat , and native predatory birds, such as the Australian Magpie , butcherbird species , Laughing Kookaburra , currawongs , crows and ravens , shrike-thrushes and reptiles such as goannas. Another threat to the birds is from humans; many nests are trampled on during breeding season because the nests are hidden close to the ground and therefore difficult for passers-by to spot.Evolution
Both island subspecies are nearer in genetic distance to mainland populations of ''leuconotus'' than to each other; Dirk Hartog Island is 2 km from the mainland while Barrow Island is 56 km from the mainland. Gene flow between the populations existed at the beginning of the present interglacial period, some 8,000 to 10,000 years ago, at a time when sea levels were lower and both islands connected with the mainland.There are three theories as to how the three races of White-winged Fairywren could have evolved. The first suggests that black-and-white plumage is an ancestral condition and, following separation of the three populations, blue-and-white plumage evolved in the mainland species. The second hypothesis suggests that black-and-white plumage evolved convergently on the two separate islands. The third suggests that black-and-white plumage evolved once from the blue-and-white ancestral condition, and later the mainland species re-evolved blue plumage.
The distribution of the three bi-coloured fairywren species indicates their ancestors lived across New Guinea and northern Australia in a period when sea levels were lower and the two regions were joined by a land bridge. Populations became separated as sea levels rose, and New Guinea birds evolved into the White-shouldered Fairywren, and Australian forms into the Red-backed Fairywren and the arid-adapted White-winged Fairywren.
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