Biziura lobata

Geographic Range

Australian musk ducks ( Biziura lobata ) are endemic to southern Australia. This species is subdivided into two genetically isolated populations, eastern and western, by the Nullarbor plain, an arid treeless desert at the head of the Great Australian Bight. Populations are also found on Kangaroo Island and in Tasmania, separated from Australia by Backstairs Passage and Bass Strait. Historically, Australian musk ducks were thought to have been flightless but now are known to fly long distances to colonize ephemeral wetlands after inland rain. They also disperse locally based on band recoveries. These sightings might suggest movement between the two populations in low numbers but it remains unclear if this occurs.

• Biogeographic Regions
• australian australian
  • native native

Habitat

Australian musk ducks are endemic to deep-water wetlands, river systems, and coastal waters of temperate Australia. In the spring they move to locations where permanent water exists that has substantial cover vegetation, such as rushes and cattails. Australian musk ducks have been observed on ephemeral wetlands on the Nullarbor plain after major flooding and occasionally forage in marine habitats.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools
• coastal coastal

• Wetlands
• marsh marsh

• Other Habitat Features
• agricultural agricultural
• riparian riparian

Physical Description

Australian musk ducks are large, strongly sexually dimorphic, stiff-tailed ducks with elongated tail feathers well adapted for diving and maneuvering in water. The legs are positioned far back on the body, making it difficult for maneuvering on land. Males are almost entirely blackish-brown with finer pale barring and speckling. The head is nearly black on the crown and nape and visibly more freckled buff on the cheeks and neck. The breast is a whitish-buff barred and freckled blackish-brown. The tail and wings are completely black while the feet are a blackish-grey. Males sport a large black to grey pendulous lobe under their bill dangling towards the water. During display the lobe inflates, by blood pressure, to the size of a golf ball. Males are substantially larger than females, weighing up to 3.6 kg and measuring 92 cm from bill to tail. Females are considerably smaller than males, weighing as little as 0.9 kg and measuring 61 cm. Females are identical in plumage and bare parts but display only a rudimentary lobe. Juveniles look much like females except for a bit of yellow on the front half of the lower mandible. It takes some time for juveniles to reach full size, the lobes of males increase in size with time

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful
• ornamentation ornamentation

Reproduction

There is no special or mutual precopulatory behavior in Australian musk duck reproduction. Males copulate with any females he manages to attract through his display activities. This absence of mutual precopulatory displays supports the probability that a promiscuous mating system exists in the species. As the spring breeding season approaches, Australian musk ducks flock on permanent water. There, males attract females through a combination of vocal and mechanical sounds as well as visual posturing which occurs from mid-July through early August. Some or all of the display postures are shared between eastern and western populations. Vocalizations differ markedly between these regions. The role of the musky pheromone for which Australian musk ducks are named is unknown, but it probably plays a role in mate attraction, male-male competition, or both. The odor only occurs in adult males and almost exclusively breeding males and may originate from the preen gland at the base of the tail. No preliminary displays are associated with actual mating. The male suddenly mounts and copulates with one of the females he has attracted. Following copulation, the female goes into a dense growth of rushes and construct her nest. During displays of the male, a hierarchy forms that appears in increasing degrees of modification and exaggeration of normal behavior. The postures of the display become increasingly more unlike normal swimming formation and the time intervals between displays become more constant and predictable. There are three main types of displays produced by the male; the “paddling kick,” the “plonk-kick,” and the “whistle kick.” The “paddling kick” includes a vigorous backward thrust of the feet, in which a sheet of water is thrown upward and backwards six feet or more. This is repeated at irregular intervals of several seconds. The “plonk kick” is the most commonly observed display and is made up of variable tail cocking, lobe and throat enlargement, and a simultaneous kick by both feet. Water is thrown out laterally, and both legs are momentarily lifted from the water as they are pulled backwards. As the feet enter the water their outstretched webbing strikes the surface producing a distinctive “plonk” sound. Kicks are repeated at intervals of approximately three seconds, with only slight variation. As females become attracted, the “plonk kick” is replaced by the “whistle kick.” Extreme tail cocking, lobe enlargement and throat inflation are associated with the display, which consists of a relatively weak lateral kick of both feet as well as a simultaneous sharp whistle. Between kicks the body is flexed upward to an extreme degree, the bill is raised and the tail is bent forward until it touches the back. The interval between whistle kicks averages over three seconds. If a female is not attracted, the male will resume “plonk kicks." If a female is attracted, the whistle kicks will proceed in a long, unbroken series. “Onlooker” males sometimes approach the group and, if they move too close to the female, the displaying bird will rush toward them across the water, or dive and attempt to attack them from below. The victim retreats usually but sometimes a vicious battle occurs with biting, wing beating, scratching amid a frenzied splashing of water. Smaller and weaker males are often injured, so there is a distinct advantage for larger and stronger males. Another notable display, the “splash-dive” occurs when other males are on site while the displaying male dives quickly amid a great splash of water thrown up as the bird disappears from view. This display appears to have a hostile or threat function.

• Mating System
• polygynous polygynous

Breeding season occurs from July or August through December or January. Clutches have been observed as late as January. Females build their nests in the dense growth of rushes. The nest can be built on the branch of a tree that has been partially submerged which happens often during the flooding of lowlands and in rainy years. Flooded cutting grass is an important nesting habitat and there will be a decline in nesting activity in years with retreating water levels. Such areas flood seasonally, and depth may not be sufficient for nesting in any given year. Australian musk ducks are capable of surviving long enough to experience favorable breeding conditions repeatedly. Nest materials in cutting grass sites consist of dry cutting grass stems and small amounts of down, nests in trees are made of sticks and bark. Most nests possess hoods composed of folded grass stems. The normal clutch size is 2 to 3 eggs but numbers as much as 5 to 6 have been reported. The female lays eggs and tends to the young. Females lay unusually large, elliptical, green eggs. Nest parasitism may occur and Australian musk ducks may be facultative nest parasites. The incidence of parasitism in these ducks, the hatching success of host-brooded eggs, and the degree of foster-parental care given to the young need further research. Sexual maturity in Australian musk ducks is delayed at 2 to 3 years old.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Female Australian musk ducks tend to young entirely on their own. Chicks are precocial, swimming and diving shortly after hatching. Occasionally they ride on the mothers back as she swims partially submerged. The chicks will grasp the feathers of the mother’s neck and, during times of danger she may even dive with the young clinging to her. Usually only one or two chicks survive in one clutch. Chicks are covered with dark brown down at hatching. The young remain with the mother for several months. She provides them the most part of their food until they are full-grown. The male doesn’t take part in incubation or protection.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Australian musk ducks have a relatively long lifespan. In captivity they have been known to live around 23 years. Little information regarding lifespan was found for wild populations.

Behavior

Australian musk ducks frequently appear in flocks during the breeding season, otherwise they can be independent or appear in small groups. Most literature describes the mating behavior of Australian musk ducks due to its unique character. There are few descriptions of social behavior. Australian musk ducks are aggressive. In captive breeding programs males are kept away from offspring, and they are generally kept separate from other waterfowl species because Australian musk duck are likely to attack them. In cases where Australian musk ducks are kept in captivity with other birds, they terrorize almost all other waterfowl by attacking them underwater and their appearance consistently causes a fast, general retreat to the shore by all other ducks. In general, male Australian musk ducks are dominant to females and males may be more active than females and range over greater distances. Australian musk ducks have demonstrated remarkable abilities to mimic the calls of other waterfowl, as well as mechanical and human sounds. Calls of immature, wild Australian musk ducks show only a rough resemblance to vocalizations of adult males and suggest a combination of social imprinting, learning, or practice is involved in vocal transmission from one generation to the next. The calls of captive Australian musk ducks differ depending on the region from which they originated and, when reared in isolation from wild ducks performing adult calls, captives never develop the wild type call even after as many as 25 years. Young ducks likely listen to mature adult calls and practice repeatedly in a social context. The duration of this vocal development period is unknown but may be more than a year. This learning requirement may be why male Australian musk ducks spend a considerable amount of time observing the advertising displays of other males.

• Key Behaviors
• flies
• natatorial natatorial
• diurnal diurnal
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary
• social social
• dominance hierarchies dominance hierarchies

Home Range

There is no known literature regarding the home range of Australian musk ducks. Because of band recoveries, it is well known that these ducks disperse locally and may move between eastern and western populations. They tend to colonize newly flooded areas.

Communication and Perception

Australian musk ducks communicate through vocalizations, visual postures, and mechanical sounds. The most notable form of communication is the male's splashing displays in a lek. These displays can be so loud and conspicuous that they can be heard from half a mile away. Males emit an unusual whistling call as well as a “plonk call” of which the origin is unknown. Males also emit a musky odor, although no substantial evidence has been found to associate a response from females. Females emit very few calls and are relatively silent. Vocalizations of captive ducks differ between regions (eastern and western Southern Australia) and are unlike those called by wild birds of the same species. Regional dialects are acquired through social context by repeated observation of adult males as well as a combination of social imprinting, learning or practice. Australian musk ducks, which have a notably large brain, also have the ability to mimic other waterfowl, mechanical sounds, and complex human sounds.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• mimicry mimicry

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Australian musk ducks obtain their food almost exclusively by diving. The diet consists primarily of aquatic animals and plants. They generally limit their feeding to shallower areas where submersed and/or immersed vegetation is abundant. The diet is composed of freshwater yabbie, freshwater shrimp, snails, freshwater mussels, and insects. Plants eaten include both marsh and upland species and are limited almost exclusively to seeds. Sex and age differences in food use exist: males eat mainly mollusks (60% adult male, 30% adult female, and 7% immature), trichopterans (36% adults, 18% immature), and Marsiliaceae (36% adult males, 23% adults females, 14% immature). Food composition varies little through the seasons. In captivity males are known to prey on the offspring of conspecifics and other waterfowl species.

• Primary Diet
• carnivore carnivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• birds
• amphibians
• fish
• insects
• terrestrial non-insect arthropods
• mollusks
• aquatic crustaceans

• Plant Foods
• seeds, grains, and nuts

Predation

Australian musk ducks are too large to be eaten by fish and will dive from a site when a hawk or an eagle appears. There was no other information found on the potential predators of Australian musk ducks in the literature.

Ecosystem Roles

Nest parasitism may occur in Australian musk ducks as a response to local crowded conditions. Not much is known about the frequency of parasitism in this species, including the hatching success of host-brooded eggs and the degree of foster-parental care given to the chicks. It is believed that they are facultative parasites and the large size of their eggs (larger than any of the Anatidae ) could correlate with their ability to retain-heat due to a reduced amount of parental incubation if lain in another ducks nest. The diet of Australian musk ducks is almost entirely of animal origin. They consume the larva and adults of aquatic insects as well as mollusks and crustaceans including large crayfish. Occasionally they consume small ducklings as well as fish and frogs. Australian musk ducks are extremely aggressive and in captivity they have been known to terrorize other waterfowl by attacking them underwater.

Economic Importance for Humans: Positive

Presently, Australian musk ducks are not important as a game species because of their dull gray color and tendency to rarely be in flight, making them poor targets. They rarely fly during daylight hours and many hunters believe the musky odor renders the meat unfit for consumption. During the 1930's Australian musk ducks were used for food in the Mandura district of Western Australia. In the 1900's colonists of Flinders islands, in Bass Strait, collected the lobes of male Musk Ducks, dried them, and placed them in their stored clothing. The musky odor was believed to have a pleasing scent and served well as a perfume and fumigant.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known adverse effects of Biziura lobata on humans.

Conservation Status

Australian musk ducks are of no importance as a game species. They do however tend to become entangled in fishing nets and drown. Their dependence on permanent swamps that are in danger of being drained for agriculture purposes may cause conservation problems for the species in the future. Although the population of Biziura lobata appears to be decreasing, the decline is not rapid enough to approach the thresholds of the IUCN Red list category to justify a listing as vulnerable currently.

Additional Links

Encyclopedia of Life

Contributors

kassondra hendricks (author), Northern Michigan University, Alec Lindsay (editor), Northern Michigan University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Attiwill, A. 1981. Possible nest parasitism in the Australian stiff-tailed ducks (Anatidae: Oyurini). Emu , 81: 41-42.

Birdlife International 2012, 2012. "Biziura lobata" (On-line). IUCN Redlist. Accessed January 21, 2013 at http://www.iucnredlist.org/details/100600363/0 .

Gamble, K. 1966. Breeding Biology and Food Habits of the Musk Duck ( Biziura Lobata ). Master's Thesis, Univeristy of Wisconsin (WI) , 1: 1-40.

Guay, P., R. Chesser, R. Mulder, A. Afton, D. Paton, K. McCracken. 2010. East–west genetic differentiation in Musk Ducks ( Biziura lobata ) of Australia suggests late Pleistocene divergence at the Nullarbor Plain. Conservation Genetics , 11: 2105-2120.

Guay, P., R. Mulder. 2005. Isolation and characterization of microsatellite markers in musk duck ( Biziura lobata : Aves), and their application to other waterfowl species. Molecular Ecology Notes , 5: 249-252.

Johnsgard, P. 2010. Ducks, Geese, and Swans of the World- Tribe Oxyurini: Stiff-Tailed Ducks . Nebraska: University of Nebraska.

Johnsgard, P. 1966. Behavior of the Australian Musk Duck and Blue-Billed Duck. The Auk , 83: 98-110.

Johnsgard, P. 1965. The Elusive Musk Ducks. Papers in Ornithology , 30: 1-6.

Livezy, B. 2002. Phylogeny and comparative ecology of stiff-tailed ducks (Anatidae: Oyurini). Wilson Bulletin , 107: 214-234.

McCracken, K., A. Afton, D. Paton. 2000. Nest and eggs of Musk Ducks (Biziura lobata) at Murray Lagoon, Cape Gantheaume Conservation Park, Kangaroo Island, South Australia. South Australian Ornithologist , 33: 65-70.

McCracken, K., P. Fullagar, E. Slater, D. Paton, A. Afton. 2002. Advertising displays of male Musk Ducks indicate population subdivision across the Nullarbor Plain of Australia. Wildfowl , 53: 137-154.

Ogilvie, M., S. Young. 2002. Wildfowl of the World . London: New Holland Publishers (UK) Ltd.