Indicator: IW-33 Abundance and distribution of waterbirds

Data

Waterbird Survey Locations

Waterbird Survey Locations

Figure 1. Ten aerial survey bands (each 30 km in width), every two degrees of latitude, crossing eastern Australia and providing estimates for up to 50 species of waterbirds in October each year (1983-2004). Letters identify seven particular wetlands: Styx River wetlands (A), Lake Hope (B), Paroo River overflow lakes (C), Macquarie Marshes (D), Menindee Lakes (E), Lowbidgee floodplain (F) and Curdies Inlet (G).

Waterbird Abundance

Fig. 2. Estimates of numbers of waterbirds of up to 50 different taxa counted during aerial surveys in October each year 1983-2004 along survey bands across eastern Australia (see Fig. 1): a) all ten survey bands: b)most southerly survey bands (1-3); c) middle survey bands (4-6) and; d) most northerly survey bands.

Waterbird Abundance

Fig. 3. Estimates of numbers of waterbirds (dashed line)and numbers of species (continuous line) of up to 50 different taxa counted during aerial surveys in October each year 1983-2004 on three wetlands in eastern Australia (see Fig. 1): a) Styx River wetlands; b) Lake Hope and; c) Paroo River overflow lakes.

Waterbird Abundance

Fig. 4 Estimates of numbers of waterbirds (dashed line) and numbers of species (continuous line) of up to 50 different taxa counted during aerial surveys in October each year 1983-2004 on three wetlands in eastern Australia (see Fig. 1): a) Macquarie Marshes; b) Lowbidgee and; c) Curdies Inlet.

Eastern Australian Waterbird Survey

(Source: Kingsford, R and Porter, J 2005, unpublished data, Eastern Australian Waterbird Survey).

Waterbird numbers across eastern Australia have exhibited a decline since 1983 (Fig. 2a). The most significant decline occurred between 1984-1986, with further declines after 1991 (see Fig. 2a). The annual average number of birds during the first three years of the survey was about 1,100,000; 1986-1995 about 405,000 and 1996-2004 about 238,000. The distribution of this decline varied between different parts of the continent (Fig. 2). Estimates of waterbirds in the northern four survey bands (7-10; see Fig. 1) were highest in 1983 and 1984 but subsequently there has been little trend in the numbers of waterbirds between 1985 and 2004 (Fig. 2b). In contrast estimates of waterbirds in the central survey bands (4-6) and southern survey bands (1-3) have shown downward trends (Fig. 2c, d), similar to total numbers of waterbirds.

Styx River wetlands

Total numbers of waterbirds were highest in 1983, 1984 and 1989, 1990. Since 1990, numbers of waterbirds have remained low because the area has largely remained dry. Years where numbers were high reflected widespread flooding and creation of habitat for waterbirds. There is no clear trend in abundance or numbers of species (Fig. 3a).

Lake Hope

There was no indication of any trend in either abundance or numbers of species (Fig. 3b). During flood periods a wide range of different species, often in large numbers and high densities occur, probably reflecting the abundance of food available (invertebrates and aquatic plants).

Paroo River overflow lakes

There was no trend in numbers of waterbirds or numbers of species on the Paroo River wetlands (Fig. 3c).

Macquarie Marshes

The building of dams and subsequent diversion of water from the Macquarie River have significantly reduced flows and area inundated in the Macquarie Marshes by at least 40-50%. Waterbird abundance and numbers of species estimated have declined significantly over time (Fig. 4).

High river flows are also an important trigger for the breeding of colonial waterbirds in the Macquarie Marshes. Annual flows (1978,1986-1996) were significantly related to total colony size (number of nests) and sizes of six nesting Ciconiidae (Intermediate Egret Ardea intermedia, Rufous Night Heron Nycticorax caledonicus, Glossy Ibis Plegadis falcinellus, Straw-necked Ibis Threskiornis spinicollis, Australian White Ibis Threskiornis molucca and Royal Spoonbill Platalea regia) colonies. Breeding of most colonial waterbirds in the Macquarie Marshes was positively related to flow in the three months before breeding and triggered when flows were usually above 200,000 ML. Generally colony sizes were significantly less (100,000 over 11 years) than would be expected without diversions of water upstream. Numbers of annual breeding events also declined with water diversions from natural to current development estimates: ten to seven (1963-1973); eight to seven (1974-1984), eight to five (1985-1995). Between 1996 and 2004, there were only four breeding events, including none between 2001 and 2004, the longest period known without breeding.

The Lowbidgee floodplain

Numbers of waterbirds and numbers of species have declined significantly on the Lowbidgee floodplain (Fig. 4b). From more than 300,000 ha in the early 1900s, at least 76.5% has been destroyed (58%) or degraded (18%) by dams (26 major storages), subsequent diversions and floodplain development. Diversions have reduced the amount of water reaching the Lowbidgee floodplain by at least 60%.

Over 19 years (1983-2001), waterbird numbers estimated during annual aerial surveys collapsed by 90%, from an average of 139,939 (1983-1986) to 14,170 (1998-2001). Similar declines occurred across all functional groups: piscivores (82%), herbivores (87%), ducks and small grebe species (90%), large wading birds (91%) and small wading birds (95%), indicating a similar decline in the aquatic biota that formed their food base. Numbers of species also declined significantly by 21%. The Lowbidgee floodplain is an example of the ecological consequences of major water resource development.

Curdies Inlet

There were no trends in numbers of waterbirds or numbers of species. Both indices exhibited high variability over time, particularly abundances.

Effects of permanent flooding on floodplain lakes

Overall, mean density of waterbirds on unregulated floodplain lakes was significantly higher compared with regulated floodplain lakes. Mean numbers of species on floodplain lakes was also significantly higher on unregulated lakes compared with regulated floodplain lakes. Three of the five functional feeding groups, (ducks and small grebes, herbivores and small wading birds) reflected this pattern, possibly indicating that invertebrate populations and aquatic vegetation were similarly affected. Numbers of piscivores and large wading species and their densities were similar between regulated and unregulated lakes, possibly because exotic fish species thrived in regulated lakes.

What the data mean

There are long term declines in total numbers of waterbirds across eastern Australia but these are largely in the south on some major wetlands (e.g. Macquarie Marshes and Lowbidgee).

There has been a significant long-term decline in river flows to the Macquarie Marshes as a result of river regulation and subsequent diversions upstream. Waterbird abundance and numbers of species have declined significantly over a corresponding period.

At least 76% of the Lowbidgee floodplain has been destroyed by dams, diversions and floodplain development, reducing the amount of water reaching the floodplain by at least 60%. Waterbird numbers have collapsed by 90%.

Reduction of hydrological variability, particularly removal of natural drying periods affects the ecology of regulated floodplain. Mean density of waterbirds and mean numbers of species on unregulated floodplain lakes in eastern Australia were significantly higher than regulated floodplain lakes (permanently flooded as water storages).

Data Limitations

In October of each year, waterbirds in eastern Australia are counted from the air on about 2000 wetlands (100 hours flying). Most waterbirds were identified to species, although species in four groups could not be separated: small egrets (3 species), small grebes (2 species), small (>20 species) and large (>5 species) migratory waders. Aerial surveys of waterbirds are imprecise but this does not affect their use in detecting temporal and spatial changes in abundance or species richness.

See Eastern Australia Aerial Survey report for full description of methodology and limitations.

Issues for which this is an indicator and why

Inland Waters - Response of biota - Waterbirds 

Waterbirds are important culturally, socially, scientifically and as a food resource. Different functional waterbird groups provide some indication of potential changes to other aquatic biodiversity, the aquatic food web and nutrient cycles. They also provide an opportunity to indirectly explore potential effects of river management and degradation on entire ecosystems. Different waterbird species feed on a wide range of aquatic fauna and flora that form part of the food web of an aquatic system. There are the ducks (e.g. blue-billed duck Oxyura australis, grey teal Anas gracilis) that feed predominantly on small invertebrates, herbivores (e.g. black swans Cygnus atratus, Eurasian coot Fulica atra), piscivores (fish feeders, e.g. Australian pelican Pelecanus conspicillatus and cormorants Phalacrocorax sp.), small wading birds (Charadriformes) and large wading birds (Ciconiiformes). The abundance and distribution of species is indicative of the condition of individual species, and of water bird species collectively.

Other indicators for this issue:

Inland Waters - Habitat scale influences - Wetlands 

The distribution and abundance of waterbirds is closely connected to the occurrence of floods and wetland inundation during wet years. Severe reductions in wetland extent in Australia have reduced the available habitat as well as the numbers and breeding success of native waterbirds. The abundance and distribution of species is indicative of the condition of individual species, of water bird species collectively, and of the condition of wetland ecosystems more broadly.

Other indicators for this issue:

Biodiversity - Pressures on biodiversity - Changed hydrology 

The distribution and abundance of waterbirds is closely connected to the occurrence of floods and wetland inundation during wet years. Severe reductions in wetland extent in Australia have reduced the available habitat as well as the numbers and breeding success of native waterbirds. Changes in the abundance and distribution of species could therefore also be indicative of changes in wetland hydrology.

Other indicators for this issue:

Biodiversity - Species, habitats and ecological communities - Conservation status of species and ecological communities 

Waterbirds are important culturally, socially, scientifically and as a food resource. Different functional waterbird groups provide some indication of potential changes to other aquatic biodiversity, the aquatic food web and nutrient cycles. They also provide an opportunity to indirectly explore potential effects of river management and degradation on entire ecosystems. Different waterbird species feed on a wide range of aquatic fauna and flora that form part of the food web of an aquatic system. There are the ducks (e.g. blue-billed duck Oxyura australis, grey teal Anas gracilis) that feed predominantly on small invertebrates, herbivores (e.g. black swans Cygnus atratus, Eurasian coot Fulica atra), piscivores (fish feeders, e.g. Australian pelican Pelecanus conspicillatus and cormorants Phalacrocorax sp.), small wading birds (Charadriformes) and large wading birds (Ciconiiformes). The abundance and distribution of waterbird populations is indicative of the condition of individual species, of water bird species collectively, and of the condition of wetland ecosystems and ecosystems more broadly.

Other indicators for this issue:

Biodiversity - Species, habitats and ecological communities - Condition of freshwater biodiversity 

The health of populations of waterbird species is an indicator of the overall condition of the aquatic system. A decline in bird numbers provides a warning that the natural ecological functioning of the aquatic system is at risk.

Other indicators for this issue:

Biodiversity - Species, habitats and ecological communities - Condition of wetlands and riparian vegetation 

The health of populations of waterbird species is an indicator of the overall condition of the aquatic system, which includes riparian vegetation. A decline in bird numbers provides a warning that the natural ecological functioning of the freshwater system is at risk.

Other indicators for this issue:

Coasts and Oceans - Contributions and pressures between the coasts and oceans and land - Condition of species at the land-ocean interface 

Changes in waterbird abundance or distribution could be indicative of changes occurring in either marine or terrestrial systems.

Other indicators for this issue:

Coasts and Oceans - Contributions and pressures between the coasts and oceans and inland water - Condition of species at the inland waters-oceans interface 

Changes in waterbird abundance or distribution could be indicative of changes occurring in either marine or freshwater systems.

Other indicators for this issue:

Land - Contributions and pressures between the land and inland water - Condition of species at the land-inland waters interface 

Changes in waterbird abundance or distribution could be indicative of changes occurring in either terrestrial or freshwater systems.

Other indicators for this issue:

Land - Contributions and pressures between the land and the ocean - Condition of species at the land-ocean interface 

Changes in waterbird abundance or distribution could be indicative of changes occurring in either marine or terrestrial systems.

Other indicators for this issue:

Further Information

Eastern Australia Aerial Survey