Thursday, May 31, 2012

>Oxyura vittata (Lake Duck)

Lake Duck

Lake Duck
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Species:O. vittata
Binomial name
Oxyura vittata
(Philippi, 1860)

Females
The Lake Duck (Oxyura vittata) is a small South American stiff-tailed duck. It is also called the orArgentine Blue-billArgentine Lake Duck, orArgentine Ruddy Duck.
The Lake Duck occurs in Argentina, Chile, Paraguay, and Brazil in southern South America.
It is notable for possessing, in relation to body length, the longest penis of all vertebrates; the penis, which is coiled up in flaccid state, can reach about the same length as the animal itself when fully erect, but more commonly is about half the bird's length. It is theorized that the remarkable size of the spiny penis with its bristled tip may have evolved in response to competitive pressure in these highly promiscuous birds, removing sperm from previous matings in the manner of a bottle brush.
Although most male birds have no penis, ducks have a long corkscrew penis, and the females have a long corkscrew vagina, which spirals in the opposite direction. The males often try to force copulation, but the complex mating geometry allows the females to retain control—most of the forced copulations do not result in successful fertilisation.


>Oxyura maccoa (Maccoa Duck)

Maccoa Duck

Maccoa Duck
O. maccoa, male
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Species:O. maccoa
Binomial name
Oxyura maccoa
(Eyton, 1838)

At San Diego Zoo
The Maccoa Duck (Oxyura maccoa) is a small (48-51 cm) long African stiff-tailed duck.
Adult males have a chestnut body, a blue bill and a black head. Adult females have a grey-brown body, with a dark grey bill and a dark brown crown, nape and cheek stripe.
This duck breeds in two main areas: eastern Africa from Sudan and Ethiopia to Tanzania and west to eastern Zaire, and southern Africa from Zimbabwe to Cape Province, South Africa. Their breeding habitat is shallow fresh waters, and they are also found in brackish and saline lakes in winter.
Rarer than previously believed, it is uplisted from a species of Least Concern to Near Threatened status in the 2007 IUCN Red List.




>Oxyura leucocephala (White-headed Duck)

White-headed Duck

White-headed Duck
Male in summer
Female
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Species:O. leucocephala
Binomial name
Oxyura leucocephala
(Scopoli, 1769)
The White-headed Duck (Oxyura leucocephala) is a small stiff-tailed duck.
Adult males have a grey and reddish body, a blue bill and a largely white head with a black cap and neck. Adult females have a grey-brown body with a white face and a darker bill, cap and a cheek stripe.

Male in winter
This duck breeds in Spain and North Africa, with a larger population in western and central Asia. Their breeding habitat is large tracts of open water with dense stands of aquatic plants to provide cover and nesting sites. Individuals are fairly frequently reported well north of their breeding range, but as with many wildfowl the status of these extra-limital records is clouded by the possibility of escapes from collections.
These birds dive and swim underwater. They are omnivorous, with vegetable matter predominating. They are reluctant to fly, preferring to swim for cover.
This duck is considered endangered due to a large reduction in populations in the last ten years. Most of this decline is due to habitat loss and hunting, but interbreeding of the Spanish population with the introduced Ruddy Duck (Oxyura jamaicensis) is a more recent threat. This has led to the attempted eradication of the American species from western Europe.
The White-headed Duck is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

>Oxyura jamaicensis (Ruddy Duck)

Ruddy Duck


Ruddy Duck
Male
Conservation status

Least Concern (IUCN 3.1)
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Species:O. jamaicensis
Binomial name
Oxyura jamaicensis
(Gmelin, 1789)
Subspecies
  • O. j. jamaicensis (Gmelin, 1789)
    (North American Ruddy Duck)
  • O. j. rubida (Wilson, 1814) (disputed)
  • O. j. andina Lehmann, 1946
    (Colombian Ruddy Duck)
  • O. j. ferruginea (Eyton, 1838)
    (Andean Ruddy Duck)
Synonyms
Erismatura jamaicensis
The Ruddy Duck (Oxyura jamaicensis) is a small stiff-tailed duck.

Male on the left, female on the right

Female
Their breeding habitat is marshy lakes and ponds throughout much of North America, and in South America in the Andes. They nest in dense marsh vegetation near water. The female builds her nest out of grass, locating it in tall vegetation to hide it from predators. A typical group of young ranges from 5-15 ducklings. Pairs form each year.
Adult males have a rust-red body, a blue bill, and a white face with a black cap. Adult females have a grey-brown body with a greyish face with a darker bill, cap and a cheek stripe. The southern subspecies ferrugineais occasionally considered a distinct species. It is separable by its all-black face and larger size. The subspecies andina has a varying amount of black coloration on its white face; it may in fact be nothing more than a hybrid population between the North American and the Andean Ruddy Duck. As the Colombian population is becoming scarce, it is necessary to clarify its taxonomic status, because it would be relevant for conservation purposes.
They are migratory and winter in coastal bays and unfrozen lakes and ponds.
These birds dive and swim underwater. They mainly eat seeds and roots of aquatic plants, aquatic insects and crustaceans.
As a result of escapes from wildfowl collections, they are now established in Great Britain, from where they have spread widely into Europe. This duck's aggressive courting behaviour and willingness to interbreed with the endangered native White-headed Duck, Oxyura leucocephala, of southern Europe has caused some concern.
Due to this, there is now a controversial scheme to extirpate the Ruddy Duck as a British breeding species.

>Oxyura vantetsi (New Zealand Stiff-tailed Duck)

New Zealand Stiff-tailed Duck

 



New Zealand Stiff-tailed Duck
Conservation status
Fossil
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Species:O. vantetsi
Binomial name
Oxyura vantetsi
Worthy, 2005
The New Zealand Stiff-tailed Duck (Oxyura vantetsi) is an extinct duck species from New Zealand which is known only from subfossil remains. It was first described as a distinct species by Trevor H. Worthy in 2005.
The New Zealand Stiff-tailed Duck was closely related to the Australian Blue-billed Duck (Oxyura australis) but its bones were about one tenth smaller than those of its Australian relative. The holotype was found in 1967 at Lake Poukawa in Hawke's Bay, North Island, New Zealand and remains in the collection of the Museum of New Zealand Te Papa Tongarewa. The specific name honours the late Australian ornithologist Gerard Frederick van Tets (1929–1995) who first recognized the relationship of this species with the stiff-tailed ducks in 1983. Because the bones of the New Zealand Stiff-tailed Duck were unlabeled, it was not until 2004 that Trevor H. Worthy from the Museum of New Zealand Te Papa Tongarewa identified 19 bones out of 13,000 fossil remains of waterfowl found in the Holocene deposits at Lake Poukawa. The fossil remains consist of left humeri, distal left humeri, right humeri, distal right humeri, and proximal right humeri. The New Zealand Stiff-tailed Duck presumably became extinct due to overhunting by the Māori in the 16th century.

>Oxyura australis (Blue-billed Duck)

Blue-billed Duck

Blue-billed Duck
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Species:O. australis
Binomial name
Oxyura australis
(Gould, 1836)
Range of Oxyura australis
The Blue-billed Duck (Oxyura australis) is a small Australian stiff-tailed duck, with both the male and female growing to a length of 40 cm (16 in). The male has a slate-blue bill which changes to bright-blue during the breeding season, hence the duck’s common name (see photo). The male has deep chestnut plumage during breeding season, reverting to a dark grey. The female retains black plumage with brown tips all year round. The duck is endemic to Australia's temperate regions, inhabiting natural inland wetlands and also artificial wetlands such as sewage ponds in large numbers. It can be difficult to observe due to its cryptic nature during its breeding season through autumn and winter. The male duck exhibits a complex mating ritual. The blue-billed duck is omnivorous, with a preference for small aquatic invertebrates. BirdLife International has classified this species as Near Threatened. Major threats include drainage of deep permanent wetlands, or their degradation as a result of introduced fish, peripheral cattle grazing, salinisation and lowering of ground water.


Taxonomy

The Blue-billed Duck was described in 1836 by ornithologist John Gould. The specific name australis is derived from the latin for "southern" and hence Australian, while the generic name is derived from the latin oxy- "sharp" and ura "tail".


Description

The tail-feathers for both the male and female are made up of thick, spine-like shafts. The tail is usually held flat on the surface of the water, or held erect when defensive. The male also holds the tail erect during courtship displays. The feet are quite powerful, which aids in swimming and diving. The duck sits low in the water in comparison to other ducks. During breeding season, apart from the aforementioned bright-blue bill, the male's head and neck are glossy black, and the back and wings are a rich chestnut. During the non-breeding season, the head changes from its glossy black to black with grey speckles,and its body changes from chestnut to dark grey. Some males retain breeding plumage throughout the year. The female’s plumage does not change throughout the year. Its head is dark brown, and the back and wings consist of black feathers with a light-brown tip, giving a mottled appearance, although the National Parks and Wildlife publication on O. australis refers to bands on each feather rather than a single feather-tip colouration. The female's bill is dark grey-brown, and its feet are grey-brown, while the male’s feet are grey. Both sexes have brown irises. Immature Blue-billed ducks resemble the adult female though paler with a grey-green bill.


Distribution and habitat

The Blue-billed Duck, Oxyura australis, is endemic to Australia’s temperate regions. Its range extends from southern Queensland, through New South Wales and Victoria, to Tasmania. The species is also widespread in the south west of Western Australia. O. australis rarely appears on the New South Wales coastline except during times of drought. It is in greatest abundance in the Murray-Darling basin.
The Blue-billed Duck is almost entirely aquatic. While they have been observed on land, they have difficulty walking, exhibiting a penguin-like gait.During non-breeding season, many ducks gather in flocks totalling several hundred, especially juveniles and younger adults, in open lakes or dams in autumn and winter, far from the shore. For the rest of the year, during breeding season, the Blue-billed duck prefers deep, freshwater swamps, with dense vegetation including cumbungi Typha orientalis (broadleaf cumbungi) and Typha domingensis (narrow-leaved cumbungi); although it has appeared in lignum swamps in more coastal areas, especially in drier seasons. They have also occasionally been found in large rivers and saline water bodies such as billabongs.


Ecology and behaviour

The behaviour of O. australis depends on its breeding cycle. The ducks gather in large flocks on lakes during the winter while not breeding, although some mature adults remain in vegetative swamps and continue to breed. They will also fly more frequently, probably due to the open habitat, and escape threats by flying. While breeding, O. australis is secretive and wary, and it will swiftly and quietly dive under water if threatened, resurfacing a large distance away, rather than escape by flying. The Blue-billed Duck has a low quack, which is seldom heard. The courting repertoire of the male is very complex and elaborative. It includes such behaviour as rolling the cheek on the back, dab-preening (also sometimes performed by females), and sousing, where the head is thrown into the water in a prone position, and the back arched as if in spasm, with possibly the legs throwing spray above the body. After the courtship ritual, and a vigorous chase, copulation follows with the female completely submerged. The birds then separate and preen themselves. In preparation for laying eggs, the female builds the nest, at which time the male will mostly desert the female.


Diet

Oxyura australis is omnivorous, where invertebrates as well as seeds, buds, and fruit of emergent and submerged plants are eaten. The duck feeds underwater by sifting mud with its bill. O. australis does have a preference for small invertebrates, including molluscs and aquatic insects such as chironomid larvae, caddis flies, dragonflies and water beetle larvae. Its diverse range of food is reflective of a relatively abundant habitat. The chironomid larvae are quite common in inland cumbungi swamps, and therefore make up a large portion of the diet of O. australis during its breeding season. Blue-billed Ducks can stay underwater for 10 seconds on average while feeding.


Reproduction

There is evidence that O. australis is partly migratory, with movement from breeding swamps of inland NSW to the Murray River during autumn and winter. Frith claims O. australis is the most migratory of all Australian ducks. Marchant and Higgins discredits this regular yearly migration, due to juveniles and young adults searching for new breeding grounds, especially on the fringes of the duck’s range, with mature breeding adults often remaining. Indeed, experienced dominate adults are sedentary in breeding swamps since migration would expend energy that instead would be used for breeding. Year-long sedentary adult breeding is confirmed by the observation that the laying period of ducks in captivity is continuous, reflecting “opportunistic breeding”. Any variation in non-captive laying is in accordance to water-levels and hence abundance of food, a fact in contrast to Frith’s description of reproduction being tied to the months between September to November.Clutch size ranges from 3 to 12, the most common being 5 to 6, according to Marchant and Higgins. Large clutch sizes indicate two females laying eggs in the one nest. It appears that a female will sometimes parasitise another’s efforts at incubation, described as “facultative parasitism”, by laying “dump clutches” in nests other than her own. There is also some evidence of the duck laying its eggs in nests occupied by other water-birds. The incubation is 26 to 28 days. After hatching, the young remain in the nest for 1 day, and are then led by the female from the nest. The young are relatively independent of the parents, being able to feed themselves immediately. The female will protect her brood, including hatchlings from dump clutches of other females. At 8 weeks, ducklings are of a similar size to the parents. Within one year, most have full adult plumage. Yearlings in captivity were observed to be able to breed.


Conservation

Two substantial land uses combine to have a significant impact on the Blue-billed Duck. These are: the regulation of wetland ecosystems through drainage, flood mitigation and water harvesting; and vegetation loss due to clearing, overgrazing and salinity.Both result in smaller habitat sizes suitable to water birds. To counteract these impacts, the Department of Environment and Conservation has devised several strategies to increase the Blue-billed Duck’s population.They include retaining sustainable water flows and developing salinity management plans and farm management plans. The Australian population of Blue-billed Ducks is estimated to be 12 000, although the creation of artificial wetlands such as water treatment works disguise the number occurring in natural wetlands. The Blue-billed Duck’s vulnerable status has been de-listed for the Environmental Protection and Biodiversity Conservation Act 1999, although they are currently recognized as vulnerable in NSW, according to the Department of Environment and Climate Change NSW.
The Blue-billed Duck is listed as threatened on the Victorian Flora and Fauna Guarantee Act (1988). Under this Act, an Action Statementfor the recovery and future management of this species has been prepared. In Victoria, the Blue-billed Duck is also listed as endangered on the 2007 advisory list of threatened vertebrate fauna within the state.


Relationship with humans

The health of wetland ecosystems can be determined by the abundance of waterbird species. A decline in bird numbers provides a warning that the natural ecological functioning of the freshwater system is at risk.Despite short term gains for farmers through permanent flooding, sustainability of wetland systems would decrease. Any long-term decrease in the population of waterbirds such as O. australis, which continue to breed yearlong, irrespective of drought conditions by seeking out suitable habitat, would make excellent indicators for wetland health. Any long-term decrease in the duck’s population would therefore be caused by habitat loss through factors such as salinity and overgrazing more so than drought.


Other comments

More field research is needed into the average lifespan of O. australis in the wild; although, based on the high number of eggs in a clutch, and maturing 12 months after hatching would indicate a short life span of less than 10 years. Captive ducks were still breeding at 16 years.Further research into the accuracy of using O. australis as an indicator for habitat health, among other waterbirds, is needed, considering its ability to breed every season despite the effects of drought. Any long-term decrease in populations of O. australis would therefore more strongly reflect poor wetland ecosystem health, without the confounding effects of natural drought cycles.


Various views and plumages


>>Genus Oxyura (Stiff-tailed duck)

Stiff-tailed duck

Stiff-tailed ducks
Male White-headed Duck, Oxyura leucocephala
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Subclass:Neornithes
Infraclass:Galloanserae
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Oxyura
Bonaparte, 1828
Species
Oxyura australis
Oxyura jamaicensis
Oxyura leucocephala
Oxyura maccoa
Oxyura vittata
Stiff-tailed ducks are part of the Oxyurinae subfamily of ducks. All have, as their name implies, long stiff tail feathers, which are erected when the bird is at rest. All have relatively large swollen bills.
These are freshwater diving ducks. Their legs are set far back, making them awkward on land, so they rarely leave the water.
Their unusual displays involve drumming noises from inflatable throat-sacs, head throwing, and erecting short crests.
Plumage sequences are complicated, and aging difficult. Plumage is vital for survival because of this animals tendency to spend time in the water. Without plumage this duck would die of hypothermia because of an inability to regulate its body temperature.


Species

  • Blue-billed Duck, Oxyura australis
  • New Zealand Stiff-tailed Duck, Oxyura vantetsi (prehistoric)
  • Ruddy Duck, Oxyura jamaicensis
  • White-headed Duck, Oxyura leucocephala
  • Maccoa Duck, Oxyura maccoa
  • Lake Duck, Oxyura vittata
A fossil species from the Late Pliocene or Early Pleistocene of Jalisco (Mexico) was described asOxyura zapatanima. It resembled a small Ruddy Duck or, even more, Argentine Blue-bill. A larger Middle Pleistocene fossil form from the southwestern USA was described as Oxyura bessomi; it was probably quite close to the Ruddy Duck.
"Oxura" doksana from the Early Miocene of Dolnice (Czech Republic) cannot be assigned to any anatine subfamily with certainty.


Wednesday, May 30, 2012

>>Genus Nomonyx >Nomonyx dominicus (Masked Duck)

Masked Duck

Masked Duck
Adult male in breeding plumage
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Subclass:Neornithes
Infraclass:Neognathae
(unranked):Galloanserae
Order:Anseriformes
Family:Anatidae
Subfamily:Oxyurinae
Genus:Nomonyx
Ridgway, 1880
Species:N. dominicus
Binomial name
Nomonyx dominicus
(Linnaeus, 1766)
Synonyms
Oxyura dominica
The Masked Duck (Nomonyx dominicus) is a tiny stiff-tailed duck ranging through the tropical Americas. They are found from Mexico to South America and also in the Caribbean. Primarily non-migratory, Masked Ducks are reported as very uncommon vagrants in the southernmost United States, along the Mexican border and in Florida.
The only member of the genus Nomonyx, it is intermediate between the rather primitive Black-headed Duck (Heteronetta) and the very apomorphic true stifftails. It is sometimes included with the latter in the genus Oxyura, but apparently the Masked Ducks of our time are the descendants of a missing link in the Oxyurinae evolution, having changed but little for millions of years.
Breeding adult males have a rust-colored body with a black face and mottled wings. Adult females, winter males and juveniles have a barred brownish gray body, with 2 horizontal darkly colored stripes running through the buffy colored face.
These ducks mainly feed on seeds,roots and leaves of aquatic plants. They also eat aquatic insects and crustaceans. They feed by diving. Masked Ducks breed in any freshwater water body with marsh vegetation and surrounded by heavy tree cover. They also occur in mangroveswamps. These ducks are usually very secretive, but they are not rare and not considered threatened by the IUCN.