University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Ducks, Geese, and Swans of the World by Paul A. Johnsgard Papers in the Biological Sciences 2010 Ducks, Geese, and Swans of the World: Tribe Anatini (Dabbling or Surface-feeding Ducks) Paul A. Johnsgard University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/biosciducksgeeseswans Part of the Ornithology Commons Johnsgard, Paul A., "Ducks, Geese, and Swans of the World: Tribe Anatini (Dabbling or Surface-feeding Ducks)" (2010). Ducks, Geese, and Swans of the World by Paul A. Johnsgard. 12. https://digitalcommons.unl.edu/biosciducksgeeseswans/12 This Article is brought to you for free and open access by the Papers in the Biological Sciences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Ducks, Geese, and Swans of the World by Paul A. Johnsgard by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Tribe Anatini (Dabbling or Surface-feeding Ducks) ,-------------- I I ,I I , I MAP 62. Breeding or residential distributions of the 5alvadori duck ("5") and blue duck (liB"). Drawing on preceding page: American Wigeon that are clean and well oxygenated. These streams, Blue Duck usually at least 10 feet wide in places, provide the Hymenolaimus malacorhynchos (Gmelin) 1789 invertebrate foods on which the birds depend almost entirely. Of these foods, caddis fly larvae are prob­ Other vernacular names. Mountain duck; Saum­ ably the most important single item (Kear & Bur­ schnabelente (German); canard bleu (French); ton, 1971), as is also true of the South American pato azul (Spanish). counterpart species, the torrent duck. May fly and stone fly larvae are also eaten, as is some algae. Blue Subspecies and range. No subspecies recognized. ducks can dive readily and reportedly cling to Limited to the highland streams of New Zealand, boulders while probing under water for inverte­ including North Island south of the Coromandel brates, but most of the birds feed in water too Peninsula and the western half of South Island. shallow for diving. The soft-edged bill is used by See map 62. adults for scraping and sucking food off rocks, and Measurements and weights. Folded wing: both sexes ducklings only a few days old are adept at probing 235-49 mm (av. of 4 males 233 mm, of 6 females their bill into crevices and moving it from side to 217 mm). Culmen: males, 42-45 mm (av. 44 mm); side, or picking up solids by pulling the bill females, 40-42 mm. Weights: males, 753-1,077 g backward over the surface (Pengelly & Kear, 1970). (av. 887 g); females, 680-850 g (av. 750 g). Eggs: Social behavior. Except for family groupings, blue Average 65 x 45 mm, pale buff, 73 g. (Pengelly ducks are not gregarious, and at most will congre­ & Kear, 1970). gate at river mouths after flooding or on winter foraging areas when food shortages force them out Identification and field marks. Length 21" (54 cm). of their breeding territories. For the rest of the year Adults of both sexes are an unusual dove gray color the birds occupy exclusive foraging and breeding with a bluish sheen, except for a brownish gray territories of river habitat. These territories, pro­ crown, reddish brown spotting on the breast, and claimed by the male and defended by him against all black edging on the edges of the inner secondaries. other blue ducks and even other species such as gray The six outer secondaries also have very narrow ducks, may occupy only a few hundred yards of white tips, and the underwing is pale gray. The bill river or may be several miles long, but Kear and is pinkish white, with a black nail and pendant Steel (1971) reported five territories in a stretch of black lateral lobes near the tip; the eyes are yellow; about two and one-half miles of river. Pair forma­ and the legs and feet are dark brown. Females have tion certainly occurs after the birds are at least five less brownish spotting on the breast than males, and months old, and probably before they are a year immatures lack breast spotting completely. The full old, but the process is still essentially unknown. It is plumage is evidently attained by six months, but believed that the birds mate permanently, although birds raised in captivity retained a dark gray culmen this is still unproven. The role of the male in paren­ band until they were more than a year old (Pengelly tal care and the strong attachment to a particular & Kear, 1970). breeding area both favor the retention of pair In the field, the unusual color and mountain bonds. Further, the extended egg-laying period stream habitat preclude confusion with any other species. The strong whistled call whio (which is the basis for the Maori name for the bird, whio) is ut­ tered only by males; the female produces a rasping quack. The birds are quite tame and rarely fly, but they do fly strongly, with a fairly rapid wingbeat. NATURAL HISTORY Habitat and foods. Blue ducks at one time occurred on mountain streams of New Zealand from the tree line to sea level, but at present they are confined to mountainous regions supporting turbulent streams ••• 179 (August to at least January) also favors permanent contracted from its original one. On the North Is­ pair bonds. Copulatory behavior is apparently very land the bird is limited largely to the mountainous much like that of typical surface-feeding ducks, con­ area around Urewera and Tongariro National sisting of mutual head pumping, although the fe­ Parks, while on the South Island it is most abundant male has at times been observed to swim rapidly in Otago and Southland. However, no estimates of around and in front of the male in a manner re­ its total population are available. Competing species sembling bathing. Following copulation the male may include various insectivorous birds and the in­ assumes an erect posture, moves his head forward troduced trout which now occupy many of the low­ and back, but has not been heard to call at this land streams. Introduced mammalian predators time, as might be expected. The loud call of the have doubtless caused considerable loss of eggs and male is largely aggressive in function, but he may young (Kear, 1972; Kear & Burton, 1971). also use it to attract unmated females (Kear & Steel, Relationships. A recent review (Kear, 1972) of this 1971). peculiar species' affinities has not provided any Reproductive biology. Although the breeding season specific answers, other than to suggest that it seems is very extended, with egg records extending over a to have its greatest affinities with the typical dab­ six-month period, the majority of nest records are bling ducks of the genus Anas, although it also has for October and November, and most hatching some similarities to the perching ducks. Kear sug­ probably occurs in October. There is, however, a gests that present evidence favors retaining it with record of an adult with young as late as June. In the dabbling duck tribe Anatini. The analysis of spite of this extended breeding period, it is likely feather proteins by Brush (1976) cast doubt on its af­ that the birds breed only once a year, as there is an finities with the dabbling ducks, but failed to pro­ extended incubation and fledging period in this vide positive evidence of other relationships. species. Nest sites are usually natural burrows­ Suggested readings. Kear, 1972. under clumps of tussock grass, under logs or bushes, in rock clefts or cliff ledges, or in hollow logs or trees. Nests are often fairly close to water, and sites are probably used in successive years, especially if they were previously successful. The modal clutch size of the relatively few observed nests is 5 eggs, and the mean is 5.4, with a range of 4 to 9. The combination of relatively small clutch size and fairly large eggs is also characteristic of torrent ducks. Only the female incubates, while the male remains hidden nearby. He joins his mate on her daily forag­ Salvadori Duck ing and bathing trips, which usually last less than an Anas waigiuensis (Rothchild and Hartert) 1894 hour. The total incubation period is probably 31 to 32 days, judging from records of artificially in­ Other vernacular names. Salvadori's teal; cubated eggs. It is probable that the family remains Salvadoriente (German); canard de Salvador at the nest for nearly two days before the parents (French); pato de Salvadori (Spanish). lead the young to water, and both sexes closely at­ tend the developing brood. The fledging period Subspecies and range. No subspecies recognized. seems to be quite long, between ten and eleven Resident in mountain streams of New Guinea weeks in ducklings raised in captivity; and even above 1,300 feet. Originally reported from, but of after fledging, the birds apparently remain within doubtful occurrence on, Waigeo Island. See map their parents' territory. How long the family re­ 62. mains intact is still uncertain, but it may be until the Measurements and weights. (From Kear, 1975.) birds attain adult plumage at the age of about six Folded wing: males, 187-207 mm (av. 194 mm); months (Kear, 1972). females, 179-96 mm (av. 185 mm). Culmen: Status. This species is totally protected in New males, 35-39 mm (av. 37 mm); females, 34-38 Zealand, but nevertheless has a range considerably mm (av. 36 mm). Weights: males, 400-525 g (av. 180 ...... 462 g); females, 420-520 g (av. 469 g). Eggs: avo 58 x 43 mm, creamy white, 58 g.