DARLING RIVERINE PLAINS BIOREGION Background Report

16/08/02 Darling Riverine Plains Bioregion Background Report
breeding colonies of ibis in the Murray-Darling basin (Smith 1993). In general, there are very
few major colonial waterbird breeding sites in Australia, consequently those that exist are
extremely important. Ibis breeding is localised and uncommon and is triggered by wetland
flooding. In general terms, the bigger the flood, the bigger the breeding response (Maher
1999).
Estimated population sizes of the colonial nesting waterbird species in the three most
significant wetlands in the DRP are:
Ibis (three species): 100 000 to 150 000 Gwydir Wetlands; 75 000 to 80 000 Narran; 70
000 to 75 000 Macquarie Marshes (800 glossy ibis, 2 000 Australian white ibis, more than
12 000 straw-necked ibis);
Large egret: 10 000 to 15 000 Gwydir Wetlands; 3 000 to 5 000 Macquarie Marshes;
Intermediate egret: 17 000 Macquarie Marshes;
Rufous night heron: 10 000 to 15 000 Gwydir Wetlands;
Australian pelican: 1 000 to 1 500 Narran Lakes;
Magpie geese: eight pairs Narran; 20 pairs Gwydir Wetlands; 20 pairs Macquarie
Marshes;
Royal spoonbill: 8 000 to 9 000 pairs in Narran Lakes; and
Brolga: six to eight pairs Macquarie Marshes.
These estimated numbers confirm the significance of these wetlands within NSW and the
Murray-Darling Basin (Kingsford & Thomas 1995; Maher 1999).
The Macquarie Marshes provide habitat for more than 70 species of waterbirds, including 42
species that breed in the area, and 130 species of land birds. It is one of the few wetlands
supporting breeding colonies of all four species of egret and three species of ibis. The
threatened magpie goose has also bred in the wetlands. In 1984, the marshes supported at
least 88 000 waterbirds, considerably more than any other wetland in the area (Kingsford &
Thomas 1995).
Sixty-five species of waterbirds have been recorded from the Narran wetlands and 46 species
breed in the area (Ley 1998a; Ley 1998b; Henderson 1999a). The wetlands support the largest
recorded breeding colonies in Australia of straw-necked ibis, little black cormorant and royal
spoonbill and large numbers of sixteen other species (NPWS 2000a; Ramsar 2000). An
estimated 200 000 pairs of ibis bred in the Narran Lake Nature Reserve in 1983, the largest
breeding event ever recorded in Australia (Marchant & Higgins 1993). Smith (1993) lists the
estimated number of breeding pairs of waterbirds at Narran Lake during the period 1971 to
1991 as ranging from 50 to 200 000 pairs in any one year, and these numbers are largely
dependant on inundation and water availability. Narran wetlands flood every two to three
years on average, which is more frequent than most other wetlands in north western New
South Wales (NPWS 2000a).
Threatened species known to breed at Narran Lakes include the brolga (Grus rubicunda),
blue-billed duck (Oxyura australis), freckled duck (Stictonetta naevosa) and the most western
known breeding record of magpie geese in New South Wales. Breeding occurs in lakes and
associated channels (Ley 1998a; NPWS 2000a). Large numbers of waders, including the
threatened black-tailed godwit (Limosa limosa), also congregate on freshly exposed mudflats
after flooding, and eleven of these species are listed under the JAMBA and CAMBA
agreements (Ley 1998a).
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