WA South Coast Shorebird network Newsletter - Vol. 2

Australasian Bittern Surveys on the South Coast

Sarah Comer, Regional Ecologist at DEC Albany describes what is being done to determine the locations of south west Western Australian populations of this endangered species in order to improve conservation outcomes.

The Australasian Bittern (Boordenitj in the south west) has become of increasing conservation concern in recent times. In August 2010 the status of bittern was ‘uplisted’ from Vulnerable to Endangered, in recognition that there has been a marked decline in the population in the last 30 years. Assessments of the status of the population in 2009 estimated that less than 2000 birds remain in the wild. In recent years it has become apparent that the south-west of Western Australia is the stronghold for Australasian Bitterns in Australia. Low rainfall in recent years has resulted in many wetlands being too dry for Australasian Bittern, highlighting the importance of those that are maintaining good water levels in dry years.

In the last few years Birds Australia, the Department of Environment and Conservation and numerous volunteers have joined forces to coordinate surveys for Bitterns (both Australasian and Little) and document the status of wetlands in the south west. In DEC’s south coast region the two areas targeted for surveys in recent years are between Lake Saide and Mettler Lake in the west, and a suite of wetlands to the east of Esperance.

The best survey times are in the evenings, when birds tend to call frequently. The call is described as a loud explosive boom and has even been associated with the legend of the Bunyip around Lake Alexandrina, the Coorong and the lower Murray-Darling in South Australia (Taplin 1874). Other survey methods used to locate wetlands that may provide habitat include searching for nesting platforms and trying to flush birds from suitable habitat during the day.

The 2010 south coast surveys for Australasian Bittern around Albany were very successful with seven to nine Australasian Bittern heard calling during the Albany Bittern Campout held in October. Similarly high numbers of Australasian Bittern were last recorded in these wetlands in 1986 during the South West Waterbird Surveys (Jaensch et al 1988). A large number of volunteers contributed to the successful surveys, with over 20 people participating in surveys of the Two Peoples Bay, Waychinicup and Manypeaks wetland suites.

In late October 2010 a smaller team including Alan Clarke (DEC Science Division), Sarah Comer and volunteers Maris Lauva, John and Judy Blyth conducted the first surveys in wetlands to the east of Esperance since 1991. Esperance staff Emma Adams and Steve Butler also joined several of the Esperance listening sessions. Only four Australasian Bittern were heard calling, and these were all found in one large wetland in unallocated crown land in the Cape Le Grand/Merrivale area. This equals the highest previous record of Australasian Bittern heard and seen in the region which was recorded in 1986 (Jaensch et al 1988). However, many of the wetlands that previously had Australasian Bitterns calling and that were visited during the October surveys are now dry or did not appear to have good food resources for bittern.

Photo of Bittern by
Patrick Gillespie

In spring 2011 surveys will continue along the south coast, and several previously unsurveyed wetlands will be targeted. In addition efforts will be made to document exact wetland habitat requirements for this species. Anyone interested in participating in surveys of south coast wetlands should contact Robyn Pickering 9312 1671 or Sarah Comer 9842-4500.

References:
Jaensch, RP; Vervest, RM; and Hewish,MJ 1988. “Waterbirds in Nature Reserves of South-Western Australia 1981-1985: Reserve Accounts” RAOU report No. 30.
Taplin, G. (1874). The Narrinyeri: an account of the tribes of South Australian