BIRD: linking the biodiversity community
Records of Blue-billed Duck in the south-west, Source; Victorian Fauna Display 2009 female Blue-billed Duck female Musk Duck female Blue-billed Duck, note tail feathers
The Blue-billed Duck (Oxyura australis) is a stiff-tailed diving duck.
Its genus name Oxyura is derived from the Greek oxys -sharp and oura-tail. The adult male has a distinctive sky-blue bill, glossy black head and chestnut body plumage, which is most evident during the breeding season but may remain throughout the year. Non-breeding plumage in males can vary and the bill can appear grey in partial eclipse or dark green in full eclipse plumage. Females are brownish-grey with pale barring and do not have plumage change. It can be difficult to distinguishing between males in full eclipse plumage, females and juveniles.
Non breeding male, female and immature Blue-billed Ducks can appear similar to the female Musk Duck, which is also a stiff-tailed diving duck. Distinguishing features include more rounded head of the Blue-billed Duck and a concave bill rather than the triangular bill of the Musk Duck. The Blue-billed Duck is noticeably smaller than the Musk Duck, males being about 60% shorter and females 30% shorter (Marchant & Higgins 1990, Simpson & Day 1999).
The Blue-billed Duck occurs in Australia's temperate regions, in both southwest Western Australia and the east. The highest concentrations in eastern Australia are in southern Victoria. The Australian population is estimated at 12,000 breeding birds (DEH 2000), although the majority are found on artificial wetlands, for example the main site for this species in Victoria is the Melbourne Western Treatment Works at Werribee. Counts of waterbirds on Victoria's wetlands over five years (1988-1991) indicate the Blue-billed Duck population could be at least 1600 in Victoria (Peter 1991). If the populations on artificial wetlands/treatment ponds were excluded a more accurate reflection of Blue-billed Duck status in natural habitats would emerge, where flocks in excess of 90 birds are uncommon and many wetlands support less than 10 birds.
The South West region is an important area for this species, in Victoria there are only 25 wetlands that have records of 100 or more Blue-billed Ducks, 14 of these are in the South West; Lake Bookaar, Lake Carchap, Lake Colongulac, Lake Corangamite, Lake Jollicum, Lake Linlithgow, Lake Milangil, Lake Oundell, Lake Yallakar, Lake Modewarre, Tower Hill, Unnamed Freehold, Lake Yambuk and Western Treatment Works at Werribee. There are four wetlands in the South West where breeding has been recorded; Kaladbro Swamp, Lake Buninjon, Natimuk Lake and Tower Hill (Du Guesclin pers. comm.).
In addition to the above wetlands, other important natural wetlands for the Blue-billed Duck in the South West of Victoria are; western district lakes near Lake Corangamite (Lake Terangpom, Lake Gnarpurt, Lake Rosine, Lough Calvert and Cundare Pool). Lake Corangamite is now unsuitable due to extremely high salinity (166,000 EC in June 2005). Deep Lake, Lake Tooliorook, Lake Modewarre, Lake Murdeduke, Lake Purrumbete, Lake Wendouree, Lake Turangmoroke, Lake Bolac, Condah wetlands, sections of the Glenelg River and lakes in the Horsham area, Kurrayah Swamp, Dock Lake and Lake Witton are also areas known to have provided habitat for the Blue-billed Duck (Emison et al 1987, Hewish 1988, Peter 1991, AVW 2004). Note: this is not intended to be a complete list of every wetland that has a record of Blue-billed Ducks but rather wetlands which have a high probability of occurrence provided conditions are suitable.
Habitat & Ecology
The Blue-billed Duck inhabits fresh to saline, deep permanent open wetlands and deep, densely vegetated lakes. During the breeding season (November - March) there is a tendency to disperse to deep freshwater wetlands that have abundant aquatic and emergent vegetation although many birds remain on large wetlands (Hewish 1988). In winter they may congregate in large flocks on large clear lakes and more saline wetlands, preferring open water usually away from the shoreline. The level of movement is likely to be influenced by seasonal conditions such as rainfall, lake levels and salinity. Suitable breeding sites may hold winter flocks, provided they contain dense marginal vegetation and large expanses of open water, which could explain why some males remain sedentary and retain full breeding plumage into winter. Nests are mostly solitary and constructed in spring on low trampled swamp vegetation such as rushes and sedges.
The Blue-billed Duck feeds on variety of aquatic insect larvae, molluscs and aquatic plant material including leaves and seeds. They have a diving habit and stay underwater for up to 30 seconds per dive (Emison et al 1987, Marchant & Higgins 1990).
The main threat is loss of suitable wetland habitat through drainage, salinisation, lowering of groundwater and lake levels, degradation to natural wetland vegetation (aquatic and emergent) and loss of suitable breeding habitat. The high concentration of Blue-billed Ducks on areas such as the Melbourne Western Treatment Works at Werribee tends to disguise what has happened to populations on natural wetlands which have been impacted upon by reduced water levels and higher salinity levels in recent years.
The long term impacts from the now banned use of lead shot is unclear, but may pose an on-going problem in some waters which were subject to heavy hunting in the past. Lead poisoning is known to occur at a much higher incidence for diving ducks (Pain 1992).
Impacts from hunting may have been a factor in the past, for example in 1987 it was recorded that 61% of Blue-billed Ducks counted on Victorian wetlands were on waters open to hunting and 2.1% of these ducks were illegally harvested, this equated to an estimated 1.3% of the entire pre-season count (Loyn 1987). As the number of viable wetlands has been reduced over the last 10 years or so due to low water levels the impact of hunting could be exacerbated as it is concentrated on fewer wetlands. This situation has been managed to some extent by altered duck hunting arrangements such as reduced hunting season and water closures. In addition, the level of illegal harvest has been minimised through improved hunter identification and licensing procedures.
Specific Management Actions from the DSE Actions for Biodiversity Conservation database
- Protect aggregations of Blue-billed Ducks from disturbance and accidental shooting, by temporary closure of wetlands (or parts of the wetlands) using the provisions in the Wildlife Act 1975.
- Characterise breeding seasons, habitat and nest requirements from directed studies of breeding biology.
- Determine land status and security of breeding and non-breeding sites and potential threats or impacts to these sites.
- Conduct surveys of potential breeding habitat to locate key breeding sites so that these can be afforded appropriate management and additional protection, if required.
- Determine characteristics of wetlands where large flocks occur.
- Encourage (exotic) predator control by DSE and landowners around key breeding wetlands.
- Monitor, on a regular basis, wetlands where flocks of >100 birds have been recorded. This should include ongoing inventory of potential threats to those sites.
- Conduct survey to identify key breeding and flocking sites on PV-managed land and rank according to population size and frequency of use.
- Investigate alternative fishing techniques to prevent by-catch of waterbirds in commercial eel fishing and other activities.
- Determine regularity, seasonality and composition of large flocks and reasons for peaks, including studies of foods.
- Encourage and promote the covenanting of appropriate land through Trust for Nature and promote wetland conservation through the Land for Wildlife scheme.
- Determine the distribution of Blue-billed Ducks in relation to wetlands of varying salinity.
- Continue to conduct annual Summer Waterfowl Counts with assistance from community groups, such as the Field and Game Australia, Birds Australia and local Field Naturalist groups, with a clear objective of locating aggregations of the species.
- Develop a detailed plan involving appropriate community consultation to restore degraded key wetlands for Blue-billed Duck. Mechanisms such as incentive schemes should be considered. (Draft DSE Action Statement provides more detail).
- Involvement of CMA’s in the management, restoration and protection of suitable habitats.
- AVW (2004) Atlas of Victorian Wildlife, Dept. Sustainability and Environment, Victoria.
- DEH (2000) Action Plan for Australian Birds 2000, Department of Environment & Heritage, Taxon summary – Blue-billed Duck.
- Du Guesclin, P. (2005) personal comment; Department of Sustainability & Environment, Portland.
- Emison W.B., Beardsell C.M., Norman F.I., Loyn R.H. (1987) Atlas of Victorian Birds, Department of Conservation Forests & Lands and Royal Australasian Ornithologists Union, Melbourne.
- Hewish M., (1988), Waterfowl count in Victoria February 1988, report prepared for Victorian Dept. Conservation Forests & Lands, Royal Australasian Ornithologists Union, Report No.52,1988.
- Loyn R.H. (1987) A report on the 1987 duck hunting season in Victoria, National Parks & Wildlife Division, Dept. Conservation Forests & Lands, Victoria.
- Marchant S., Higgins P., eds (1990) The Handbook of Australian, New Zealand and Antarctic Birds, Oxford University Press, Melbourne.
- Pain D.J. (1992) Lead Poisoning in Waterfowl: a review. In Lead Poisoning in Waterfowl, proceedings of an IWRB workshop Brussels, Belgium, IWRB special publication No.16, 1992.
- Peter J. (1991) Waterfowl count in Victoria February 1991, report prepared for Victorian Department of Conservation & Environment, Royal Australasian Ornithologists Union, Report No.79,1991.
- Simpson & Day (1996) Field Guide to the birds of Australia, sixth edition, Penguin Books Australia Ltd.
- Flora & Fauna Guarantee, Victoria, Action Statement No.174 Blue-billed Duck -link to DSE pdf
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