Mud Islands

Mud Islands Marine Reserve

The Mud Islands are located within Port Phillip Bay, south of Melbourne, Australia, approximately 10km inside Port Phillip Heads, 7km north of Portsea and 9km east of Queenscliff.

First sighted by Europeans in 1802, the Islands were originally named Swan Isles because of the large number of swans on the surrounding waters. It was not until 1836 that Lt. T M Symonds and H R Henry of the HMS Rattlesnake surveyed the Islands and called them Mud Islands.

In 1961, the area of the Islands above high water was proclaimed a State Wildlife Reserve. The central lagoon and surrounding waters of the Harold Holt Marine Reserve make up a 2500 square metre area. The Islands are listed by the International Union for Conservation of Nature as a Wetland of International Importance and are also included on the Register of the National Estate.

The land area is made up of three low-lying islands surrounding a shallow tidal lagoon connected to the sea by three narrow channels. The land area is about 50ha and the lagoon 35ha.

The islands can only be reached by boat, the most convenient departure points being Queenscliff or Sorrento. Day visitors are permitted, but overnight camping is not. There are no regular tours to Mud Islands. As the Islands are surrounded by shallow waters, visitors need to be cautious when attempting a landing. Passengers must be ferried to shore by dinghy or else wade in. Visits need careful planning to avoid the boat being stranded at low tide.

Flora and fauna

Within the reserve there are nine native vegetation communities. Seagrass meadows, sand dunes, mud flats and salt marshes support a diversity of life ranging from marine invertebrates to fish and birds. Some 70 species of birds have been recorded on the Islands, which form essential breeding, feeding and roosting areas for sea birds and waders, many of them migratory.

Wind and tide are gradually changing the shape of the islands, although they are partly stabilised by a saltmarsh of Austral Sea-blite and Beaded and Shrubby Glasswort. The dense coastal scrub on the northern island has disappeared, apparently as a result of overgrazing by rabbits. Today only a single specimen of Coastal Teatree (Leptospermum laevigatum) remains.

The isolation of the islands provides protection from predators and makes them an ideal sanctuary for breeding seabirds, notably the five and a half thousand White-faced Storm-Petrels which, during summer, lay their eggs in burrows in the loose sand of Middle Island. During the day they feed at sea on shrimps and small fish, returning at night to feed their chicks. Although there are fewer than at nearby South Channel Fort, nearly a quarter of the White-faced Storm-Petrels in Victoria breed on Mud Islands.

Silver Gulls are even more numerous. Over the past twenty-five years the breeding population has built up to nearly one hundred thousand. Given a chance, gulls readily attack the eggs and young of other breeding seabirds. The Fisheries and Wildlife Service is studying the gulls' impact.

Other seabirds nesting on Mud Islands include nearly a thousand Crested Terns, one of the largest colonies in Victoria and the only one in Port Phillip Bay. Also important to the islands are the dozen breeding pairs of Caspian Terns and, in 1983 and 1986, several pairs of Australian Pelicans. Little Penguins and Fairy Terns have bred there in the past. The mud from which the islands get their name is excellent feeding habitat for migratory waders. More than 1 per cent of the known Australian populations of four wader species, Lesser Golden Plover, Grey Plover and Mongolian Plovers and Ruddy Turnstones spend the summer around Mud Islands. More than 5 per cent of the Victorian populations of Red Knots and Great Knots, Eastern Curlew and Bar-tailed Godwit feed in Swan Bay to the west but roost on the islands at high tide. The Common Tern also roosts in exceptionally large numbers and as many as 260 have been seen there at once. Two resident waders, the Pied Oystercatcher and the Red-capped Plover, regularly breed on undisturbed parts of the islands. Lewin's Rail, another waterbird, occasionally breeds in the saltmarsh but is so shy that nesting has not been observed in some years. No land birds are resident, although many species visit. Up to 100 of the rare Orange-bellied Parrot have been seen on the islands during winter when they migrate to the Australian mainland from Tasmania. In recent years, however, numbers appear to have declined, possibly because the increasing numbers of gulls has changed the chemistry of the soil and so the vegetation on which the parrots feed. Nevertheless the islands are an important habitat for this endangered species.

Mud Islands are a permanent reserve for the management of wildlife, and the surrounding waters and mudflats are part of the Harold Holt Marine Reserves.