2 July 2011

The Australian Bureau of Meteorology (BOM) recently got in touch asking about anomalies in their weather radar over Melbourne’s Port Phillip Bay.

These anomalies have been observed for some time but it was only when bird enthusiast Lynda Chambers joined BOM that she suggested they might be flocks of birds emanating from Mud Island, since the pattern doesn’t fit any particular weather anomaly.

Straw-necked Ibis are a familiar sight in farmland around Melbourne but nowhere more than the fields around Werribee.

During winter, the movement starts in a northerly-direction in the morning (from about 6:30am) and returns south in the evening (from about 6pm). The flocks are moving between southern Port Phillip Bay, around the tip of the Bellarine Peninsula and across the Geelong Arm to Werribee.

Mud Island is part of Port Phillip Heads Marine National Park. It’s not actually made of mud. It’s founded on the Great Sands, a massive shifting bar that separates the benign northern three-quarters of Port Phillip Bay with the heavily tidal south. The island hosts spectacular colonies of seabirds, including beautiful White-faced Storm Petrels. The surrounding seagrass and channels are even breeding grounds for Bronze-Whaler Sharks. In short, it’s a very rich and incredibly important part of Port Phillip Bay.

Swan Bay and the Port Phillip Islands are collectively, identified as an Important Bird Area by BirdLife International. About 95,000 pairs of birds nest on the island, including about 56,000 pairs of Straw-necked Ibis and about 30,000 pairs of Silver Gull.

Anyone who has spent time driving between Melbourne and Geelong will be familiar with the huge wheeling flocks of Straw-necked Ibis over the freeway. It’s quite likely that most of these birds breed on Mud Island. It’s appearing likely that the radar images are, for the most part, showing these ibis, along with some Australian White Ibis and Silver Gulls, moving in the direction of Werribee. The Western Treatment Plant and the surrounding agricultural land is a significant feeding area.

If anyone has any further insights, feel free to leave them as a comment and for more information, contact:

Dr Lynda Chambers
Centre for Australian Weather & Climate Research – Bureau of Meteorology
GPO Box 1289 MELBOURNE  Vic 3001 AUSTRALIA
Phone: +613 9669 4784   Fax: +613 9669 4660
E-mail: L.Chambers@bom.gov.au

If you’d like to visit Mud Island, there are trips every month with the Friends of Mud Islands group.