Data Zone
Justification of Red List category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is stable and hence does not approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is large and does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Population justification
Over a decade ago, there were thought to be 10,000 Blue-billed Ducks in south-eastern Australia and 5,000 in south-western Australia (Wetlands International 2019). No more robust estimation has been made since, however the population is plausibly much larger. Of 9,000 counted in Victoria in 2019, over 5,400 were at the Western Treatment Plant alone (Menkhorst et al. 2019), with up to 12,000 being counted there in dry years (Loyn et al. 2014a,b). The plausible population size is therefore suspected to number between 11,000 and 19,000, with a best estimate of c.15,000 mature individuals (Menkhorst et al. 2021).
Trend justification
Although numbers vary between years (Menkhorst et al. 2018, 2019), there is no suggestion of a decline in long term counts (Clemens et al. 2019, Menkohorst et al. 2021) and therefore the population is inferred to be stable.
Blue-billed Ducks occur across much of south-eastern Australia from southern Queensland to eastern South Australia including the entire Murray-Darling basin and through wetter parts of south-western Australia (Marchant and Higgins 1990). The Western Treatment Plant in Werribee, Victoria is particularly important (Loyn et al. 2014a; Menkhorst et al. 2018, 2019). The scatter of inland records, including breeding records, suggests there may be at least some interchange between east and west, though there is no evidence that this occurs.
The species is found on terrestrial wetlands in temperate regions, that are freshwater to saline, and may be natural or artificial. It nests in rushes, sedges, Lignum Muehlenbeckia cunninghamii and paperbark Melaleuca, and it lays 5-6 eggs. It feeds on aquatic insect larvae, seeds and plant matter. During autumn and winter the species aggregates in large flocks but disperses to smaller waterbodies when breeding. Aggregations also occur during drought.
The main historical threat has been an over-use of surface water for agriculture (Kingsford 2000), but the capacity of the species both to use deeper reservoirs (Murray et al. 2012) and take advantage of inland flooding (Jaensch et al. 2009) means this is probably not having an ongoing influence. The mobility of O. australis means they can seek out refuges such as the Western Treatment Plant at times of drought (Murray et al. 2012, Loyn et al. 2014a). Hunting has also been considered a threat (Loyn 1987) but O. australis are not a legal game species in any Australian jurisdiction and key hunting wetlands are closed if they support significant O. australis concentrations (Menkhorst 2019, Menkhorst et al. 2019). Recreational boating (Stamation et al. 2016) and introduced fish (Stamation and Loyn 2008) may cause local problems for O. australis but are unlikely to cause population declines. In the future, climate change and increasing frequency of drought may impact this species.
Conservation Actions Underway
Blue-billed Ducks are regularly monitored along with game species in Victoria, where there is a strong link between counts and management (Menkhorst 2019; Menkhorst et al. 2018, 2019). They are also included in other regular waterbird count data (Clemens et al. 2019), although they are difficult to detect from the air.
Text account compilers
Vine, J., Garnett, S., Berryman, A.
Contributors
Burbidge, A. & Jaensch, R.
Recommended citation
BirdLife International (2024) Species factsheet: Blue-billed Duck Oxyura australis. Downloaded from
https://datazone.birdlife.org/species/factsheet/blue-billed-duck-oxyura-australis on 18/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 18/12/2024.