Pink-eared Duck Research Articles

Trace elements in liver and muscle tissues from wild waterfowls in Australia: Risk associated with human consumption in a global context

Trace elements in game meats remain a point of concern for both the public and policymakers alike due to the human health implications if levels present are above guideline limits. This study aimed to: (1) determine trace element concentrations (As, Cd, Hg, Pb Cr, Cu, Se, Zn) in edible portions (breast meat and liver) of the four most frequently hunted duck Anatidae species inhabiting wetlands in Victoria, Australia, to identify the risk to human health from consumption; (2) investigate landscape-scale variables that may influence the detected concentrations and; (3) review the studies available (n = 41) in duck liver and muscle tissues from the 1970s to 2024, to contextualise the detected concentrations found on a global scale. Our study shows that ducks in Victoria had trace element concentrations below tolerable daily intake (TDI) guidelines for human health with one exception: notably high Hg in a filter-feeding specialist, the Pink-eared duck (Malacorhynchus membranaceus). Yet, the only trace element concentrations that were influenced by proximity to populated centres, were As and Zn. Compared to international reports, Pb concentrations in livers and muscle of Victorian waterfowl were lower, however, Pink-eared ducks had higher Hg than other duck (Anas spp.) species. Review of the worldwide data indicate that Pb concentrations in liver tissues from all Anas species have declined from the 1970s to 2024. This is the first study to identify this trend at a global scale. International movements towards Pb-shot bans, along with phasing out of Pb in gasoline and paint are the most likely cause of declining concentrations in tissues of wild waterfowl. These findings strongly underscore the importance of legislative efforts to limit trace elements entering the environment.

The cestode genus Gastrotaenia Wolffhügel, 1938 (Platyhelminthes: Cyclophyllidea) in Australian waterfowl (Aves: Anatidae)

ABSTRACT Examination of museum collections revealed the presence of two species of Gastrotaenia Wolffhügel, 1938 (Cestoda: Hymenolepididae) in Australian anatid birds. Gastrotaenia dogieli (Ginetsinskaya, 1944) was found in the gizzard of the following species of Australian ducks from New South Wales: Anas castanea (Eyton), Anas rhynchotis Latham, Anas gracilis Buller, Aythya australis (Eyton), Chenonetta jubata (Latham) and Malacorhynchus membranaceus (Latham). Gastrotaenia cf. paracygni Czapliński & Ryžikov, 1966 was found in the proventriculus of black swans (Cygnus atratus (Latham)) from New South Wales and Victoria. The two species are reported for the first time from Australia. Specimens of Gastrotaenia without scoleces, and therefore not identifiable to species, were present in Anas superciliosa Gmelin and Biziura lobata (Shaw).

Effects of rainfall in the arid zone on waterbird abundance at a wastewater treatment plant in coastal South Australia

We investigated which species of waterbirds at Bolivar, a wastewater treatment plant in Metropolitan Adelaide, South Australia, are likely to have been immigrants from the ephemeral wetlands in the arid zone. To do this, we compared the abundance of waterbird species observed at Bolivar during the dry period in the eastern arid zone of late 2018 and 2019 with that during the subsequent wet period 2020–2022. Pink-eared Duck Malacorhynchus membranaceus, Grey Teal Anas gracilis, Australasian Shoveler Spatula rhynchotis, Hardhead Aythya australis and Blue-billed Duck Oxyura australis were all more abundant during the arid-zone dry period. By contrast, Australian Shelduck Tadorna tadornoides, Eurasian Coot Fulica atra and Black Swan Cygnus atratus showed increased abundance in spring and early summer in all years, with no marked differences between the dry and wet periods in the arid zone. Wader species that breed in the Northern Hemisphere – Sharp-tailed Sandpiper Calidris acuminata and Red-necked Stint C. ruficollis – also tended to be more abundant during the arid-zone dry year, as did Red-necked Avocet Recurvirostra novaehollandiae, whereas Pied Stilt Himantopus leucocephalus tended to be more abundant in the arid-zone wet years, with breeding by this species taking place in spring. These data suggest that Bolivar is a critically important conservation site for waterbirds and that various species use this location as a refuge during dry times in the arid zone of eastern Australia.

Bolivar Wastewater Treatment Plant provides an important habitat for South Australian ducks and waders

The populations of South Australian duck and wader species have recently decreased considerably, but their abundance at Bolivar Wastewater Treatment Plant in metropolitan Adelaide is poorly known. To help assess the importance of this site for ducks and waders, we made 25 trips to Bolivar between December 2018 and July 2020, during most of which time south-eastern Australia was experiencing a long dry period. On each trip, we observed between 11 and 26 species of ducks and waders, with a mean total of 9804 (range 2437–15,653) individuals per trip. At times, we observed several thousand Pink-eared Ducks Malacorhynchus membranaceus, Grey Teal Anas gracilis, and Australian Shelducks Tadorna tadornoides, with occasionally up to 1200 Blue-billed Ducks Oxyura australis and 2000 Hardheads Aythya australis. Several wader species that largely breed in Australia’s semi-arid and arid zones were also observed, including occasionally >1000 Red-necked Avocets Recurvirostra novaehollandiae. Five species of waders that breed in the Northern Hemisphere were also recorded fairly regularly in the summer of both 2018–2019 and 2019–2020, including up to ~2000 Sharp-tailed Sandpipers Calidris acuminata, 2000 Red-necked Stints C. ruficollis and 150 Curlew Sandpipers C. ferruginea. These observations indicate that this wastewater treatment plant is a critically important refuge site for several species of ducks and waders. Every effort should thus be made to maintain this site for the conservation of these species in the future.

Nest Construction by the Pink-Eared Duck

Nest Construction by the Pink-Eared Duck

Nondestructive Raman spectroscopy confirms carotenoid-pigmented plumage in the Pink-headed Duck

ABSTRACT A small group of pigment classes is responsible for the wide range of plumage colors in modern birds. Yellow, pink, and other “warm” feather colors of many species are attributed to carotenoid pigments, a plumage trait that has an uneven distribution across modern bird species. Carotenoid plumage pigments are especially rare among fowl (superorder Galloanseres), and until recently, the Pink-eared Duck (Malacorhynchus membranaceus) from Australia provided the only evidence that any species of waterfowl (order Anseriformes) exhibits carotenoid-pigmented plumage. We analyzed a Pink-headed Duck (Rhodonessa caryophyllacea) study skin using Raman spectroscopy, without plucking or otherwise damaging the specimen. Raman spectra confirmed that the pink feathers of Rhodonessa are pigmented with carotenoids. Spectra from Rhodonessa were similar to those from Malacorhynchus, which suggests that the same carotenoid is the primary plumage pigment in both species. Moreover, spectra from Rhodonessa were similar ...

Visual fields in Blue Ducks Hymenolaimus malacorhynchos and Pink‐eared Ducks Malacorhynchus membranaceus: visual and tactile foraging

Blue Ducks Hymenolaimus malacorhynchos (Anatidae), an IUCN Red Listed Endangered species, reside in headwaters of New Zealand rivers and feed primarily on aquatic invertebrates. However, whether such food items are detected by tactile or visual cues is unknown. That Blue Ducks may use tactile cues when foraging is suggested by the presence of specialized flaps of thickened, keratinized epidermis containing Herbst's corpuscles along the ventral margins of the upper mandibles near the bill tip. Similar bill flaps are found only in one other duck species, Pink‐eared Ducks Malacorhynchus membranaceus, that surface filter‐feed on a range of planktonic organisms. Using an ophthalmoscopic reflex technique we determined the visual fields of both species. In Blue Ducks the eyes are frontally placed resulting in a relatively wide binocular field into which the narrow tapering bill intrudes. There is a large blind area to the rear of the head. This visual field topography is similar to that of other visually guided foragers including those that take mobile prey from the water column, e.g. penguins (Spheniscidae). By contrast, Pink‐eared Duck visual fields show features found in other tactile feeding ducks: a narrow frontal binocular field with the bill falling at the periphery, and comprehensive visual coverage of the celestial hemisphere. We conclude that although Blue Ducks may take prey from rock surfaces they are primarily visual feeders of the water column and we suggest therefore that their foraging may be significantly disrupted by changes in water clarity. This introduces a previously unconsidered factor into the selection of sites for population enhancement or re‐introductions, a current conservation focus.

Activity budgets of waterfowl (Anatidae) on a waste-stabilisation pond

This study investigated the activity budgets of eight species of waterfowl on a waste-stabilisation pond known to support a large waterfowl community. Most species examined were found to use the area extensively for feeding. Pink-eared Duck (Malacorhynchus membranaceus), Australasian Shoveler (Anas rhynchotis), Grey Teal (A. gibberifrons) and Chestnut Teal (A. castanea) fed most intensively at sunrise and sunset, and rested during the middle of the day. Hardhead (Aythya australis), a diving species, Australian Shelduck (Tadorna tadornoides) and Pacific Black Duck (Anas superciliosa)—large birds that were presumably able to reach the benthos from the water's surface—fed at relatively consistent levels throughout the day. Black Swans (Cygnus atratus) steadily increased the amount of time spent feeding from dawn to dusk. The diurnal activity budgets of these Australian species were similar to those observed for other species occupying similar ecological niches elsewhere. Imminent changes to sewage treatment operations may reduce the ability of this waste-stabilisation pond to support waterfowl populations. The monitoring of activity budgets after any such changes are implemented should be an effective means of detecting any effects, negative or positive.

Waterbird abundance in eastern Australia, 1983 - 92

We examined the relationships between abundance of 16 species of waterbirds and the rainfall in eastern Australia, the rainfall west of this region, the annual Southern Oscillation index (SOI), the wetland area, and hunting in eastern Australia for the period 1983–92. Data were collected during aerial surveys of eastern Australia. For most explanatory variables, lags of up to five years before aerial surveys were also investigated during these analyses. The analyses covered all nine game species (plumed whistling-duck, Australian shelduck, Australian wood duck, pink-eared duck, grey teal, chestnut teal, Pacific black duck, Australasian shoveler, hardhead) and seven non-game species (Australian pelican, white-faced heron, yellow-billed spoonbill, freckled duck, black swan, black-winged stilt, red-necked avocet). Regression models were developed for all species apart from Australian pelicans. Rainfall and climate indices generally were most correlated with the species’ abundance. Bonferroni adjustments to significance levels meant that there were significant variables in regression models for seven of the 16 species. Abundance indices for plumed whistling-duck, chestnut teal, hardhead, black swan and black-winged stilt were related to the climate variables (rainfall, SOI) and wetland area, whereas abundance of pink-eared duck and red-necked avocets were negatively related. Abundance of chestnut teal was positively related to numbers of hunting licences sold. The results are equivocal about the role of hunting in determining waterfowl abundance, which is probably a reflection of few data points and numbers of variables included. In general, abundance indices of waterbirds appear to have decreased between 1983 and 1992, which may correspond to other factors not modelled

A comparison between saline and freshwater wetlands on Bloodwood Station, the Paroo, Australia, with special reference to their use by waterbirds

Bloodwood Station, 130 km NW of Bourke, NSW, has a diverse array of intermittently flooded wetlands raging from salinas to fresh waters, either clear, opaque or very turbid, and from relatively large (820 ha) to quite small (<1 ha). A study during 1995 followed the filling of 22 wetlands after heavy rain in January to subsequent drying or recession, and looked at the relationship between physicochemical features, aquatic plants, zooplankton, littoral invertebrates, tadpoles, and waterbirds. Wetlands were delineated into two major groups: saline and fresh, with the latter subdivided into five types — clear fresh waters, artificial tanks, vegetated pans, turbid pans, and miscellaneous. The saline lakes developed extensive beds of macrophytes some months after filling which attracted large number of waterbirds. Later, abundant Zooplankton were feed for many Pink-eared Duck. Most of the fresh waters developed large initial populations of phyllopodous crustaceans, Zooplankton and tadpoles, but these waters attracted few waterbirds. Clearer fresh waters later grew macrophytes which attracted many waterbirds, but the turbid claypans remained unattractive to waterbirds during their existence, despite harbouring a host of invertebrates. The vegetated pans, artificial tanks and miscellaneous sites attracted only a few waterbirds, but the tanks along with the persistent clear fresh waters become important as feeding and resting sites as other wetlands dried towards the year end. Few waterbirds bred on these wetlands during 1995. However, many were important as major feeding sites and formed part of a mosaic of intermittent wetlands for Australia's inland waterbirds.

Patterns of waterbird use in wetlands of the Paroo, A river system of inland Australia.

The significance of inland wetlands to Australian waterbirds has been overlooked until recently. One important area identified from regular aerial survey centres on the Paroo River in north-western New South Wales. Between April 1983 and December 1985, a period covering a major flood, waterbird populations were estimated on five wetland systems associated with the Paroo during 14 trips. Fifty- three waterbird species were recorded with the anatids, Anas gibberifrons and Malacorhynchus membranaceus, accounting for 75 per cent of total estimated populations. Most breeding events were observed in those wetlands dominated by Muehlenbeckia florulenta (lignum). Breeding accounted for shifts in waterbird populations between wetland systems. A model of waterbird usage of the five wetland systems in relation to a complete flood event is described. The importance for waterbird conservation of wetlands used for breeding and maintenance of populations between flood events, and threats to the integrity of these wetlands are discussed.

Distribution and Abundance of Ducks in the Alligator Rivers Region, Northern Territory

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of wandering whistling-duck Dendrocygna arcuata, plumed whistling-duck D. eytoni, radjah shelduck Tadorna radjah, Pacific black duck Anas superciliosa, and grey teal A. gibberifrons on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal north of the Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela plain, to provide more detailed information. The Magela floodplain was inhabited by few ducks during the wet season (November to March), but numbers then increased to dramatic peaks in the late dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) showed similar patterns, but the numbers of ducks were usually fewer. Ducks were uncommon on the shallower East Alligator and Cooper floodplains except for relatively brief periods in the wet season. The ground surveys suggested that ducks sought out the persistent swamps that characterise the Magela floodplain in the dry season. Ground surveys also indicated that aerial surveys underestimated densities; on the basis of correction factors calculated from the ground surveys, peak numbers on the five floodplains were roughly estimated to be 400 000 wandering whistling-ducks, 70 000 plumed whistling-ducks, 20 000 radjah shelducks, 50 000 Pacific black ducks, and 50 000 grey teal. Pink-eared ducks Malacorhynchus membranaceus and hardhead Aythya australis were recorded sporadically in low numbers. The Alligator Rivers region acted as a dry season refuge for large concentrations of ducks because of the atypical persistence of freshwaters on the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain. The large aggregations appear to be unique in Australia.

Australian Waterfowl Do Not Necessarily Breed on a Rising Water Level

Nest sites of waterfowl (pacific black duck, grey teal, pink-eared duck, maned duck and Australian shelduck) in 200 tree holes were monitored monthly over 4 years in a swamp complex near Booligal, N.S.W. The most nests occurred in 1978 following a complete drawdown and reflooding of the swamps. A rising water level on an already full swamp did not result in significant nesting activity. The response to the drawdown and filling was not a simple matter of more aquatic vegetation and invertebrates being produced at this time. Samples of nekton were taken by net and quadrats, and plankton was taken by nets. The results indicated that there were more of the common invertebrates in other seasons than in that following the filling, and vegetation did not develop fully until the 1978 breeding season was nearly finished. It is postulated that the high nesting activity related to a massive production of invertebrate detritivores, particularly Chironomus tepperi, which was stimulated by the decaying organic material from the dead aquatic vegetation (e.g. Vallisneria spiralis, Carex sp., Elaeochoris sp. and algae) of the previous full period, and the flooded dead dryland vegetation (e.g. grasses). A lack of these chironomids is suggested as the cause of the low nesting rates in other seasons, when the swamps were full and food apparently was available. It is also postulated that these and other detritivores are efficiently captured and provide a superabundant food source, at the water surface and in very shallow water, for both adults and chicks. Other invertebrates are either not available to chicks in these microhabitats or are harvested too inefficiently or slowly by adults. The concept that a rising water level per se is central to the breeding ecology of some species of ducks should be abandoned. Rather, the significant phenomena are the drawdown, and the production of detritus and detritivorous invertebrates when the wetland basin is refilled.

An Experimental Investigation of Filter-Feeding on Zooplankton by Some Specialized Waterfowl.

A study was made of the filtering ability and anatomy of the mouthparts of 4 species of waterfowl: pink-eared duck, Australasian shoveler, freckled duck and grey teal. The first 3 are highly specialized for filter-feeding on zooplankton whereas the last is a more generalized anatid. The pink-eared duck and Australasian shoveler have the filtering lamellae on the bills variously elaborated, whereas the grey teal is similar to published descriptions of the mallard. The freckled duck has bill features more characteristic of flamingoes. On the basis of anatomy it was predicted that pink-eared ducks should be able to filter the smallest particles, followed by shovelers, freckled ducks and grey teal. In feeding experiments the proportions of plankton of various sizes removed by the species was compared. For the 3 specialists the distributions of proportion removed compared with plankton size was, in general, best fitted by a threshold model as follows: y = 1.0[x &gt; P]; y = aebx[60 mu m &lt; x &lt; P], where P is a threshold size above which all plankton can be filtered, y is the proportion filtered out and x is the size class of the plankton (in mu m). Grey teal were inefficient feeders on plankton and gave results only poorly fitted by a simple linear model. The 3 specialists had significantly different threshold sizes, and the results indicated that pink-eared ducks were the most able filterers, followed by freckled ducks, then Australasian shovelers. The failure of a simple mechanistic analysis of anatomy to predict filtering ability is discussed. On the basis of the abundance of these specialized filter-feeders possibly being related to plankton abundance, counts of pink-eared ducks and Australasian shovelers were regressed against plankton counts for a semi-permanent lake in western New South Wales. No simple relationship was found, and the significance of planktivory in these species is discussed.

Bias in Food Habits of Australian Waterfowl.

Most food studies of Australian waterfowl have relied on gizzard analyses. This introduces bias because of differential digestion rates. Oesophageal and gizzard contents collected from feeding grey teal (Anas gibberifrons) and pink-eared duck (Malacorhynchus membranaceus) at 2 sites in south-western New South Wales were determined. Pink-eared duck ate 99.6% animal food (mainly chironomid larvae and ostracods); grey teal ate 74.2% animal food (mainly corixids and dipteran larvae) at one site but 63.9% plant food (mainly grass seeds) at the other. Both species contained higher proportions of animal material in their oesophagi than in their gizzards. Rank correlation analyses showed no significant relationships between oesophageal and gizzard contents in the 2 species in this study, nor in other Australian and overseas waterfowl reported in the literature. It is suggested that gizzard analysis has led to overestimation of the importance of seeds in the diet of Australian waterfowl and underestimation of the importance of invertebrates. It is recommended that future food habits studies of waterfowl use oesophageal contents from feeding birds, and results from previous gizzard studies be treated with caution.

Response by Waterfowl to Hunting Pressure: A Preliminary Study

The movements of ducks to refuges in response to hunting pressure were investigated during the opening of the 1981 duck season. Grey teal, Pacific black duck, hardhead and Australasian shoveler actively sought refuge whilst pink-eared duck did not. Some implications for management are discussed.

Notes on Subfossil Anatidae from New Zealand, Including a New Species of Pink-Eared Duck Malacorhynchus

A new species of pink-eared duck, Malacorhynchus scarletti, is described from subfossil deposits at Pyramid Valley, South Island, NZ, and is characterized by larger size. Preliminary observations indicate that subfossil specimens of Biziura from New Zealand are larger and differ qualitatively from B. lobata; for the present, the name Biziura delautouri Forbes, 1892, ought to be retained for the New Zealand form. An erroneous record of Mergus australis is corrected.

Nest Construction by the Pink-Eared Duck

Nest Construction by the Pink-Eared Duck

Waterfowl in an inland swamp in New South Wales. 2. Food

The food of nine species of waterfowl has been studied in a drought refuge during a period of moderately severe drought. The species involved were the black swan, freckled duck, black duck, grey teal, shoveler, pink-eared duck, hardhead, musk duck, and blue-billed duck. In all, 3697 gizzards were examined. Although the black swan had certain food plants in common with most other species, particularly during periods of drought, and although the black duck and grey teal had nearly identical food requirements, serious competition between these species was considered unlikely for various reasons. Otherwise, the species were well separated in their feeding places, depths of water utilized, and food collected. The value of cumbungi swamps as drought refuges is discussed and the adaptations of the waterfowl in utilizing these swamps are examined.

An Unusual Display of the Pink-eared Duck

An Unusual Display of the Pink-eared Duck