The black-necked stork (Ephippiorhynchus asiaticus) is a tall long-necked wading bird in the stork family. It is a resident species across the Indian Subcontinent and Southeast Asia with a disjunct population in Australia. It lives in wetland habitats and near fields of certain crops such as rice and wheat where it forages for a wide range of animal prey. Adult birds of both sexes have a heavy bill and are patterned in white and irridescent blacks, but the sexes differ in the colour of the iris with females sporting yellow irises and males having dark-coloured irises. In Australia, it is sometimes called a jabiru although that name refers to a stork species found in the Americas. It is one of the few storks that are strongly territorial when feeding and breeding.
Taxonomy and systematics
First described by John Latham as Mycteria asiatica, this species was later placed in the genus Xenorhynchus based on morphology. Based on behavioural similarities, Kahl suggested the placement of the species in the genus Ephippiorhynchus, which then included a single species, the saddle-billed stork. This placement of both the black-necked stork and saddle-billed stork in the same genus was later supported by osteological and behavioural data, and DNA-DNA hybridisation and cytochrome–b data. The genera Xenorhynchus and Ephippiorhynchus were both erected at the same time, and as first revisor, Kahl selected the latter as the valid genus for the two species. This and the saddle-billed stork Ephippiorhynchus senegalensis are the only stork species that show marked sexual dimorphism in iris colour.
Two subspecies are recognized E. a. asiaticus of the Oriental region and E. a. australis of south New Guinea and Australia. Charles Lucien Bonaparte erected the genus Xenorhynchus in 1855 and placed two species in it, X. indica and X. australis. This treatment was carried on into later works. James Lee Peters in his 1931 work treated them as subspecies. In 1989, McAllan and Bruce again suggested the elevation of the two subspecies into two species: E. asiaticus or the green-necked stork of the Oriental region, and E. australis or the black-necked stork of the Australian and New Guinean region. This recommendation was based on the disjunct distributions and differences in the iridescent colouration of the neck which the authors suggested might reflect different behavioural displays. This recommendation has not been followed and a subsequent study did not find consistent differences in the colours. Analysis of the cytochrome b mitochondrial sequences however showed significant genetic divergence. The genetic distance of a stork presumed to be Ephippiorhynchus asiaticus asiaticus from a confirmed individual of E. a. australis was 2.1%, much greater than the genetic distances between individual storks of the same species. The conservative treatment as two subspecies has been followed in the Australian faunal list by Christidis and Boles.
Description
The black-necked stork is a large bird, tall having a wingspan. The only published weight for this species was a single specimen at , but this is nearly 35% less than the mean body mass of the closely related and similar sized saddle-billed stork. Therefore, this specimen of black-necked stork could have been at the low end of sizes attainable or perhaps somewhat malnourished. The plumage patterns are conspicuous with younger birds differing from adults. Adults have a glossy bluish-black iridescent head, neck, secondary flight feathers and tail; a coppery-brown crown; a bright white back and belly; bill black with a slightly concave upper edge; and bright red legs. The sexes are identical but the adult female has a yellow iris while the adult male has it brown. Juveniles younger than six months have a brownish iris; a distinctly smaller and straighter beak; a fluffy appearance; brown head, neck, upper back, wings and tail; a white belly; and dark legs. Juveniles older than six months have a mottled appearance especially on the head and neck where the iridescence is partly developed; dark-brown outer primaries; white inner primaries that forms a shoulder patch when the wings are closed; a heavy beak identical in size to adults but still straighter; and dark to pale-pink legs. Like most storks, the black-necked stork flies with the neck outstretched, not retracted like a heron. In flight it appears spindly and a black bar running through the white wings (the somewhat similar looking migratory black stork has an all black wing) with black neck and tail make it distinctive.