Australasian grebe

Article and images by Dr Julie O'Connor, senior conservation partnerships officer, Sunshine Coast Council

The industrious little Australasian grebe (Tachybaptus novaehollandiae) is a fairly common sight on reed-fringed ponds across much of Australia and parts of the Pacific. It was also self-introduced to New Zealand with the first breeding pair recorded near Wanaka in 1977.

In Australia, they mainly breed from September to January in southern Australia and from January to April in the north, but will also breed out of sync to take advantage of floods occurring in other months. The nest is a floating vegetation platform around 40cm high and anchored to floating vegetation.

The Australasian grebe has a broad diet that includes a range of fish, aquatic invertebrates and occasional small frogs. They also eat their own small downy feathers, a habit which is thought to protect the gut from sharp fish bones, and/or possibly to help fight gastric parasites. They also feed feathers to their young, presumably for the same reasons. Where they coexist with the similar hoary-headed grebe, resource partitioning has been recorded, with the prey type of the 2 species overlapping by only 28%.

Nest building and incubation is shared, as is parental care. The partly precocial young can swim from birth but do not become fully independent for another 8 weeks. During the crucial first couple of weeks they will often ride on a parent’s back under a protective layer of feathers. This probably serves the dual purpose of assisting tired young and protecting them from potential predators. While adults usually gather food for the chicks and themselves by diving, they tend to trawl along the surface more frequently when chicks are on their back.

Despite their small size, grebes are great defenders of their nest and brood, chasing off larger intruders, including eels. Nevertheless, chicks can frequently fall prey to other wetland birds, including common species such as purple swamphens and dusky moorhens. A 10 year observational study carried out at a number of urban wetlands in Sydney found that 39% of chicks survived to adult plumage. Even the small adults can fall victim to some avian wetland predators. In 2015, naturalist, Peter Valentine observed and photographed the deliberate stalking and predation of an adult Australasian grebe by a black-necked stork in North Queensland.

Parental favouritism and sibling rivalry has been observed in Australasian grebes. Sometimes favouritism can simply consist of ignoring young, but in other cases, it can involve active attacking of the less favoured. Researchers also observed the favoured chicks attacking their less fortunate siblings.

If you’ve ever watched a grebe diving, you may have wondered at the impressive speed and duration of the dive. Part of the secret is in the design of its densely packed waterproof feathers. With the underside of the feathers held at right angles to the skin, grebes are able to trap large air bubbles that enable them to float. When they press their feathers against the body, the process is reversed – air bubbles are released, reducing buoyancy and allowing the grebe to sink below the surface.

The grebe’s feet are another special adaptation to its aquatic lifestyle. While ducks and geese have webbed feet, the three front toes of the Australasian grebe are lobed rather than webbed. This creates an enhanced streamline effect when the grebe swims or dives, as the lobes alternately spread and retract.

Its small size and aesthetically unremarkable feathers may have served to protect the Australasian grebe from some of fashion’s worst excesses in the early 1900s. This was not so for its larger cousin, the great crested grebe. A writer to Adelaide’s Evening Journal (on 11 May 1907) quaintly extolled the virtues of the plumage of the great crested grebe, praising not their functionality for the grebe, but their value as a decorative addition to the popular headwear of the day:

Grebe, which makes a tentative reappearance every now and then, chiefly for children, is really very pretty wear for a fresh young girl. And a set consisting of toque, stole, and muff can look quite smart, and is certainly becoming with its pretty satiny white feathers shading to brown…

Fortunately for the grebe, fashions come and go.

References

Australasian little grebe, nzbirdsonline.org.nz
Mo, Matthew and Waterhouse, David R. 2015. Aspects of the breeding biology of the Australasian grebe (Tachybaptus novaehollandiae) in urban wetlands, Waterbirds 38 (3): 296-301.
Olsen, P. & Joseph, L. 2011. Stray Feathers: Reflections on the Structure, Behaviour and Evolution of Birds. CSIRO Publishing, Collingwood, Victoria
Valentine, P. 2016. An observation of Black-necked stork hunting and eating an Australasian grebe. North Queensland Naturalist 46 pp 86-89.