Swan Bay and Port Phillip Bay Islands

Country/territory: Australia

IBA Criteria met: A1, A4i (2009)
For more information about IBA criteria please click here

Area: 3,377 ha

Protection status:

BirdLife Australia
Most recent IBA monitoring assessment
Year of assessment Threat score (pressure) Condition score (state) Action score (response)
2008 high not assessed not assessed
For more information about IBA monitoring please click here

Site description
The IBA is comprised of the Swan Bay area (including Lake Victoria, Freshwater Lake, Portarlington sewage works and Rabbit, Duck and Swan Islands), Mud Islands and a number of small man-made stacks, including Wedge Light, Popes Eye, South Channel Island and some navigation markers across southern Port Phillip Bay. Shorebirds regularly move between these locations to feed and roost but rarely move to the other areas of Port Phillip Bay, which are identified as separate IBAs. The habitat at Swan Bay consists of intertidal flats fringed by saltmarsh with a patch of coastal heathland to the north around Edwards Point. The natural habitat on the sand islands (Rabbit, Duck, Swan) at the entrance to the bay is dominated by saltmarsh, with some coastal heathland on Swan and Rabbit Islands. To the east of the bay lies Lake Victoria, a shallow, saline lake with extensive mudflats bordered by saltmarsh and sedgeland. To the north-west of Lake Victoria is Freshwater Lake, a smaller body of water, fringed by herbland, that is sometimes completely dry. The Mud Islands complex consists of a group of low, sandy islands with shrubland, saltmarsh, calcarenite outcrops and, at low tide, exposed mudflats. Popes Eye and South Channel Island are rock stacks that support some infrastructure. Wedge Light is a timber structure used for navigation purposes. Swan Bay and Mud Islands are within the Port Phillip Bay and Bellarine Peninsula Ramsar site.

Key biodiversity
The IBA is frequented by at least 20 species considered to be threatened or near threatened in Victoria (P. Menkhorst, unpubl. data) and regularly supports more than 20,000 waterbirds, including 4000 to 15,000 shorebirds and more than 10,000 nesting seabirds. In addition to the key species described above, the IBA supports significant proportions of the Victorian populations of Great Knot, Red Knot and Grey Plover; the largest breeding colonies in Victoria of White-faced Storm-Petrel (12,400 nesting burrows on Mud Islands and South Channel Island), Australian Pelican and Silver Gull; and important breeding colonies of Australasian Gannet (299 nests), Pied Cormorant, Crested Tern (2600 pairs on Mud Islands in 1999-2000) and Caspian Tern (20 pairs on Mud Islands)(Harris et al. 1980; Menkhorst 1988; Minton & Jessop 2000; Norman et al. 1998; P. Menkhorst, unpubl. data). Up to 808 Eastern Curlew and 1678 Sharp-tailed Sandpiper were recorded in the IBA in 1983-2004, but maximum counts exceeded thresholds in only two of 22 survey years and one of 22 survey years, respectively. Other waterbird species recorded in the IBA include the Banded Stilt (0 to 6000 birds in 1983-2004), Bar-tailed Godwit (219-2500 birds in 1983-2004 and 1500 birds on Mud Islands in 2006), Double-banded Plover (0-422 birds in 1983-2004), Pied Oystercatcher (37-84 birds in 1983-2004) and Red-capped Plover (82-342 birds in 1983-2004) (Barter 1992; AWSG, unpubl. data). Up to 28 Pacific Gulls have been recorded in winter on Mud Islands (P. Menkhorst, unpubl. data). Large numbers of Fairy Penguins feed in the open waters of Port Phillip Bay (Port of Melbourne Corporation 2004), and terns, including Little Tern and Common Tern, roost on Mud Islands (Lane et al. 1984). Striated Fieldwrens are frequently encountered in salt marsh habitat at Lake Victoria and around Swan Bay (Atlas of Australian Birds database; C. Tzaros pers. comm.).

Non-bird biodiversity: The Mud Islands complex supports one of the largest known stands of Austral Hollyhock (P. Menkhorst pers. comm. 2007). The southern waters of Port Phillip Bay contain populations of the Australian Fur Seal and Bottlenose Dolphin, as well as diverse marine ecosystems that have been included in marine reserves.

Recommended citation
BirdLife International (2020) Important Bird Areas factsheet: Swan Bay and Port Phillip Bay Islands. Downloaded from http://www.birdlife.org on 30/05/2020.