The estuarine ecosystems of Sydney Olympic Park provide habitat for migratory shorebirds – a group of birds that feed in the intertidal zones of bays and estuaries, and migrate from the northern hemisphere to Australia for the spring and summer months.
Migratory shorebirds (also called migratory waders) breed in Alaska, Siberia, and Japan between May and July each year, taking advantage of the northern summer before flying southward to warmer weather to escape the approaching winter. The sorts of birds that make this journey include godwits, sandpipers, stints, and knots. The smallest of these species, the tiny Red-necked Stint, travels 30,000 kilometres each year and weighs only 30 grams!
As migratory shorebirds fly to and from Australia each year they take the same route, along which they usually make a number of stopovers to rest and feed. This route is known as the East Asian-Australasian Flyway, and over four million birds travel along it each year. When these birds reach the Sydney region, they may stay for the whole summer or, after resting and feeding, they may continue southwards to Victoria, Tasmania or New Zealand.
Migratory shorebird species that have been recorded in the Parramatta River estuary (including Sydney Olympic Park) since 1992 are:
The species that most commonly occur at the Park are the Bar-tailed Godwit and Sharp-tailed Sandpiper. In recent years numbers observed during the day have been relatively low (in the order of 5-20 birds), but at night over 250 birds regularly fly in to roost at the Park.
Migratory shorebirds are typically present at Sydney Olympic Park between September and April. The birds feed at low tide on marine worms, crustaceans and shellfish found within estuarine mudflats, sandbars and saltmarsh. At high tide, they roost on low-lying areas with good visibility, located close to feeding sites.
The main habitats for migratory shorebirds at Sydney Olympic Park are:
The Park’s habitats are part of a network of migratory shorebird habitat within the Parramatta River estuary. Birds move between these habitats in response to the tide, wind speed and direction, time of day, availability of prey, disturbance and other factors. Other parts of this network include Mason Park wetlands, Homebush Bay, Hen and Chicken Bay, Iron Cove and Ermington Bay. All of these sites have an important role in meeting the habitat needs of migratory shorebirds.
As well as supporting migratory shorebirds that are resident in the Parramatta River estuary over the spring and summer months, the Park is also thought to function as a transit site for birds moving to and from summer habitats in more southerly parts of Australia. Thus the number of birds present at a particular time may be a significant underestimate of the number of birds reliant upon the Park’s habitats throughout the migratory shorebird season.
Migratory shorebirds and their habitat are protected under the Bonn Convention (Convention on Migratory Species), the Convention on Conservation of Biological Diversity, and agreements between the Australian government and the governments of Japan, China and Republic of Korea (JAMBA, CAMBA & ROKAMBA). These agreements commit the governments of each country to the protection of migratory bird habitat by actions including preservation and enhancement of their habitats and encouraging their conservation.
All of the migratory shorebirds that occur at Sydney Olympic Park are protected under the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999 as ‘matters of national environmental significance’.
Historical data shows that there has been a steady reduction in migratory shorebird populations in the Parramatta River estuary, including Sydney Olympic Park, with a sharper decrease occurring over the last 20 years. This decline has been due largely to habitat loss and disturbance. Other factors outside of Australia along the East Asian-Australasian Flyway are also contributing.
Tidal exchange was re-introduced to the Newington Nature Reserve wetland in 1997 and to the Waterbird Refuge in 2007 to provide intertidal foraging habitat for migratory shorebirds. Water levels are managed to mimic the tides, so that exposed mudflats provide foraging habitat at low tide, and shallow water and constructed islands provide roosting sites at high tide.
Strategic mangrove seedling removal prevents mangroves from colonising mudflats that provide foraging habitat for migratory shorebirds. As mangroves are protected in NSW under the Fisheries Management Act 1994, a permit is obtained to authorise this work.
Disturbance to migratory shorebird habitat is minimised by restricting access to certain wetland areas during the spring and summer months.
Predator control programs are ongoing to reduce populations of foxes and other introduced pests that may prey on migratory shorebirds.
For more information about migratory shorebirds, visit the Australasian Wader Studies Group