27 Jul 2021
Some birds search for berries and fruits to eat, other birds like to hunt for fish, and some birds snatch flying insects in the air. The migratory Bar-tailed Godwit likes to probe into mud of the Waterbird Refuge for its favourite food - benthic worms.
This species travels 22,000km annually. Starting after the breeding season, they travel from the northern hemisphere to south-eastern Australia via the East Asian-Australasian Flyway. Arriving in early spring after their journey, they have on average lost half of their body weight, and seek estuarine mudflats with plenty of food to offer and low disturbance so that they can eat, rest and recuperate. At the end of their stay, they leave in late summer to start the second leg of the journey back to northern Asia and Alaska in search of breeding grounds. Each year this return trip requires fuel; in this case, benthic invertebrates that live in mud.
At the Waterbird Refuge the Sydney Olympic Park Authority has been closely monitoring Bar-tailed Godwits since 2007. The majority of the Bar-tailed Godwit population of the Parramatta River estuary visit the Waterbird Refuge each year, with 91% recorded over the 2020-21 season. To help with management of the wetland, it was time to check the populations of this bird’s favourite food – the benthic worms.
The Authority’s benthic monitoring investigated invertebrates present in the mudflats by taking monthly samples of the sediment and sieving out any worms present. These were then identified and counted, providing an idea of the richness and abundance of species. The monitoring found that amongst other species, a healthy number of Polychaetes are present. Polychaetes are a diverse group of segmented worms otherwise known as bristle worms. Capitelids and Nereids were the most abundant present at the Waterbird Refuge. Captelids are small head-side down burrowers and Nereids crawl through the mud using their small hairs and leg-like appendages for locomotion.
These Polychaetes of different shapes and sizes are a good source of food for Bar-tailed Godwits, with the highest number of Polychaetes recorded at the Waterbird Refuge in early February 2021, around the same time that the highest number of Bar-tailed Godwits were recorded in the Waterbird Refuge (27th January).
Although Polychaetes such as Capitelids and Nereids may not be considered a delicacy for us, it can be acknowledged as internationally renowned food of the Bar-tailed Godwit and many other migratory shorebirds in need of a good feast!
Bar-tailed Godwits, internationally protected migratory shorebirds, probe their long bills into estuarine mudflats in search of food © Jon Irvine
|The Authority undertake benthic monitoring to see what is on the menu for migratory shorebirds at the Waterbird Refuge||
Many segmented worms are available at the Waterbird Refuge, ensuring the Bar-tailed Godwits a good meal during their non-breeding season