Birds

Shorebirds are commonly distinguished by their long beaks and equally long legs and at Port Phillip Bay there are three species used by scientists as indicators for the health of shorebirds more generally in the bay:

• red-necked stint
• curlew sandpiper
• sharp-tailed sandpiper.

An indicator species gives scientists a measure of the habitat the particular species lives in.

Western Port is renowned for its high biodiversity, particularly a high count of waterfowl.

To conclude, there’s an update on the beloved little penguin colonies on Phillip Island and at St Kilda.

Shorebirds are declining around the world, including populations that spend their non-breeding period in Australia. Most migratory shorebirds spend the non-breeding period in tropical and temperate regions, and breed in the Northern Hemisphere’s arctic tundra.

Shorebirds that breed in western Alaska and eastern Siberia, and spend the non-breeding season in Australia (and New Zealand), migrate along the East Asian-Australasian Flyway.

In order to conserve migratory shorebirds it is important to know where shorebird habitats are and to have monitoring programs that are able to detect changes in shorebird populations so that the right decisions are made to protect the shorebirds’ habitat.

• Roosting shorebirds in Port Phillip Bay are declining in line with the decline in populations throughout the world in the last 20 years.
• The migratory shorebirds can often stop at wetlands along the East Asian-Australasian Flyway, relying on local flora and fauna for nourishment. Land degradation and land-use change along the flyway is contributing to the overall decline in shorebird numbers.
• The pattern of migration is so ecologically important that the birds are subject to international agreements such as the Ramsar Convention (1971) to protect migratory birds and their habitats.  

Shorebird counts take place at high tide during roosting, twice a year at eight coastal sites:

• Laverton
• Altona
• Werribee
• Avalon
• Moolap Salt Works
• Lake Connewarra Area
• Swan Bay
• Mud Islands

The results, over the period 1981-2010 showed that of 16 migratory shorebird species examined at Port Phillip Bay and the Bellarine Peninsula Ramsar site, 10 species (62%) had significantly declined since 1981. Curlew sandpipers and lesser sand plovers show particularly strong declines.

Other results included:

• Marsh sandpiper numbers significantly increased during the monitoring period.
• Grey-tailed tattler numbers dropped dramatically between 1990 and 1991, then remained stable at very low levels from 1991 to 2010.

The results also included findings on resident species:

• Masked lapwing numbers decreased significantly at Laverton-Altona and Swan Bay and Mud Islands, but increased significantly at the Moolap Salt Works.
• Australian pied oystercatcher numbers decreased significantly at Swan Bay and Mud Islands and increased significantly at Moolap Salt Works.
• Neither resident species changed significantly overall when their annual count data from the five major shorebird areas were combined.

Tidal heights have a strong influence on the numbers of shorebirds that feed on the Port Phillip Bay’s coastal flats. The number of shorebirds reach a peak during the spring low tides and reduce in numbers during the autumn high tides.

Key areas have been identified where shorebirds are able to forage at high tidal levels. These are recognised as being crucial for conserving the shorebirds.

What we need to know

Several species of threatened shorebirds also use the WTP site (in low numbers because they are threatened) and it is unclear how the upgrades at the WTP have affected these species. Species such as eastern curlew are very vulnerable and numbers have declined at the WTP, for example. While the decline there is similar to other sites, a site-specific cause is possible.

The decline in nutrients (or some geomorphological process changing average particle size of sediments in the WTP intertidal area, especially at The Spit) may have triggered a change from large polychaete worms to other taxa, which could affect this large species of migratory shorebird. Ruddy turnstone and several other species have also declined at the WTP. The reasons have not been investigated.

Studies of benthic invertebrates revealed some striking changes over this short period of time, with a large decline in worms and a corresponding increase in crustaceans (mainly amphipods) in the middle of the decade. This is likely to affect some shorebird species.

Invertebrates are very diverse in the north of Port Phillip Bay, in part due to the additional nutrients from the Western Treatment Plant (WTP), Yarra River and Kororoit Creek inflows. This provides nutritious feeding grounds for shorebirds.  The nutrient rich water discharged to the bay supports the high level of infauna productivity, which in turn supports the high populations of intertidal shorebirds. 

At least 253 bird species have been recorded in Western Port, including 102 species of waterbird and 151 other species, including bush birds (passerines), raptors, cockatoos and parrots, pigeons, cuckoos and quail.

Western Port regularly supports over 10,000 individual shorebirds and over 10,000 individual waterfowl.

The area has considerable biodiversity and is recognised as a wetland of international importance under the Ramsar Convention (1971).

In 2010, Western Port was also listed as an Important Bird Area as it is regularly home to a significant proportion of the global population of eastern curlew, red-necked stint and Australian pied oystercatcher. It also hosts declining numbers of two threatened species, the fairy tern and the orange-bellied parrot. 

Long-term analysis conducted on 39 species showed 22 species had declined, including:

• four species of duck,
• five species of fish-eating bird (cormorants, terns and pelicans),
• one species each of grebe, gull and heron, and
• ten species of shorebird.

Only two species (Australian pied oystercatcher and straw-necked ibis) increased significantly over the same time period.

Several threats are known to affect waterbirds:

• Waterbirds are sensitive to disturbance by people and their pets, so public access to important roosting and foraging sites may disturb birds using those areas.
• Loss and degradation of shoreline vegetation through inappropriate land use practices reduces both roosting and breeding habitat.
• Erosion of foreshore substrate also reduces available feeding and roosting habitat.
• Sediment exports from the catchment have potentially contributed to past seagrass declines, which affect invertebrate and fish communities and thus, the birds that rely on those marine fauna for prey.

What we need to know

There is a considerable decline in the threatened fairy terns in both Port Phillip Bay and Western Port (and more broadly across Victoria) over the past 50 years, while cormorants and pelicans have remained stable.

The reasons for this decline are unclear but researchers consider recreational fishing is having an impact. Further study of fish takes and fish stocks is required.

Up to 1,500 little penguins come ashore each night on Summerland Beach, Phillip Island, at the world-famous ‘Penguin Parade’, an iconic Victorian tourist attraction.

Little penguins pick their breeding time according to the annual peak in ocean productivity when there is plenty of food.

Increased sea surface temperatures are expected to influence the penguins because sea-surface temperatures are linked to the penguins’ breeding patterns.

Higher sea surface temperatures lead to earlier breeding and heavier chicks.

This sounds good for the little penguins. However, studies have shown that the birds suffer increased moulting due to the heat and this ultimately impacts their survival through to adulthood.

Other threats to penguins include:

• the impact of winds
• southern oscillation index
• increased ocean acidification
• impacts on food supply like fishing and the survival rate of juvenile fish, and
• plastics and pollution.

Despite their proximity to Victoria’s largest cities, Melbourne and Geelong, Port Phillip Bay and Western Port are quite healthy overall.

To measure the environmental health of the bays, the Commissioner for Environmental Sustainability worked with marine scientists who identified 36 indicators across the six key topics you see on this website.

The indicators were chosen because they best ‘indicate’ whether that key topic is healthy.

Here’s how the birds measured up: