The Werribee & Avalon IBA consists of wetlands from the mouth of the Werribee River to Avalon saltfields, on the shores of Port Philip Bay, south-west of Melbourne. Much of the area consists of the sewage treatment ponds of the Western Treatment Works, combined with coastal mudflats past the Point Wilson Explosives Area, to include all of the Avalon saltworks and Limeburners Bay. The sewage treatment works treats 60% of Melbourne's wastes in a series of aerobic and anaerobic lagoons and Lake Borrie, with patches of reeds and other wetland vegetation, and irrigates treated effluent onto adjacent pastures. The coast includes saltmarshes, intertidal mudflats and a small area of mangroves. The site is flat, has an annual rainfall of about 750 mm and mean maximum temperatures of 24°C in January and February to a mean minimum of 7°C in July. All of this area except for the Avalon saltworks is included within the Port Phillip Bay & Bellarine Peninsula Ramsar Site which also includes extensive areas of pastoral grasslands of little ornithological value within the Western Treatment Plant.
Significant populations of Banded Stilt (max 1846 in 2004), Curlew Sandpiper (declining, max 5074 in 2004 but previously 13,323), Red-capped Plover (max 202 in 1996), Double-banded Plover (max 519 in 1996 but subsequent counts below 310; previous max 955 and long-term mean 508), Black-fronted Dotterel (max 303 in 1983), Pied Oystercatcher (max 159 in 1985) and Red-necked Avocet (max 1166 in 2003), Black Swan (max 6879 in 2006), Hardhead (max 9784 in 2004), Pacific Black Duck (max 2231 in 2001), Great Crested Grebe (max 633 in 2005), wetland passerines, raptors, foraging site for Fairy Tern, breeding site for Pied (700 pairs; Environment Australia 2001) and Little Pied Cormorants and regular records of Australasian Bitterns, but probably not breeding (ARI database on behalf of Melbourne Water Corporation and Australian Wader Studies Group Database). Vunerable Fairy Tern recorded in 31 of 196 (16%) and near threatened Flame Robin recorded in eight of 196 (4%) Atlas of Australian Birds surveys from 1998 to 2008 (Atlas of Australian Birds database). Striated Fieldwrens are common in suitable habitat (G. Dutson pers. obs 2007); recorded in 67 of 196 (34%) Atlas of Australian Birds surveys from 1998 to 2008 (Atlas of Australian Birds database).
Non-bird biodiversity: Contains numbers of the Striped Legless Lizard and Growling Grass Frog (threatened in Australia) and Fat-tailed Dunnart (threatened in Victoria).
Pressure/threats to key biodiversity
Saltmarshes and weedy areas used by Orange-bellied Parrots should be managed specifically for this species. Melbourne Water has an ongoing responsibility to manage the sewage treatment systems in ways which maintain the area's ornithological importance.
Conservation responses/actions for key biodiversity
Melbourne Water has adopted an adaptive management approach to the Environment Improvement Program (which will change nitrogen levels in the treatment process) and is implementing a series of detailed investigations to improve understanding of relationships, dependencies and biotic pathways for Ramsar values, as well as monitoring those values. Routine rabbit and fox control occurs at the Western Treatment Plant and The Spit Nature Conservation Reserve. Fox control programs are being stepped up at The Spit. A predator-proof fence has been constructed around all saltmarsh areas in the Point Wilson Explosives Area. Melbourne Water and Parks Victoria have prepared a conservation management plan for the Western Treatment Plant and the Spit Reserve. Management plans are also in preparation for Limeburners Bay and Avalon Beach.
The Spit Nature Conservation Reserve.
A mix of State and private ownership - Melbourne Water is responsible for Sewage Treatment areas; Victorian Parks for reserves, intertidal areas and Bay waters; Cheetham Salt Company owns the salt works.
Site access / Land-owner requests
Access to the Western Treatment Plant for birdwatching is available only between 06:30-21:00 by permit ($20 for a two-year permit plus a deposit for a key). Applications can be obtained by telephoning Melbourne Water on 131722 (08:00-17:30 Monday to Friday) or over the counter at 89 Millers Road, Brooklyn, 09:00-16:00 on week days; see http://www.melbournewater.com.au/content/sewerage/western_treatment_plant/bird_watching_and_fishing.asp
The nomination was prepared by Kevin Wood. The Australasian Wader Studies Group provided shorebird data. Waterfowl counts made by Bob Swindley and Arthur Rylah Institute for Environmental Research, DSE, on behalf of Melbourne Water Corporation (through Will Steele); data compiled by Phoebe Macak and Richard Loyn.
BirdLife International (2023) Important Bird Areas factsheet: Werribee and Avalon. Downloaded from
http://www.birdlife.org on 01/02/2023.