The Australasian Bittern is an endangered waterbird which occurs mainly in Australia and New Zealand. It inhabits tall, dense, emergent, reedy vegetation growing in shallow freshwater wetlands, where foraging, roosting and breeding all take place. They are often difficult to see: When a person walks through a bittern’s wetland, the bird’s initial reaction is to freeze and assume an erect posture — with its neck outstretched and its bill pointing skyward.  Sometimes a hiding bittern even sway with the breeze to enhance its concealment. When this pose is combined with its cryptic plumage (mottling, streaks ands striations), a bittern is easily overlooked alike.

The Australasian Bittern is threatened across its range by loss and degradation of suitable wetlands. This poorly know species is listed as Endangered (EPBC Act and IUCN Red List). It was only recently listed under the EPBC Act (early 2011) following nominations from Birds Australia. The distribution of the species from the first Atlas (1977-1981) and the New Atlas August 1998 to July 2003 and August 2003 to July 2008 are shown below. The number of 10-minute grids in which the species was recorded has decreased between each five year period.

For the past two years we have appealed for observers to submit their records of Australasian Bitterns to us. We have been surprised by how few reports have reached us and fear that the species may be rarer than has been thought. We feel that there is an urgent need to organise a Bittern survey, looking for both Australasian and Australian Little Bitterns across south-east and Western Australia this spring and summer. In Western Australia surveys are being coordinated by BAWA. We would like observers to get out and check their local wetlands for these species. Due to their skulking nature, they are difficult to detect and two different types of survey are proposed - listening surveys and wetland walks. To get involved download the ID kits at the bottom of the page and contact us for more information.

Populations of Australasian Bitterns

The population of Australasian Bitterns in Australia is perilously low. Based on the survey conducted in 2009–10, minimum and maximum numbers of mature Australasian Bitterns that could potentially inhabit each wetland were calculated.  The minimum figure is the actual number of birds recorded, while the maximum is the largest number that each wetland could potentially support.

Listening Surveys

Both Bittern species call at dusk and dawn through the spring and early summer at their breeding sites. Listening surveys should be conducted around sunset or sunrise. The number and location of calling birds should be recorded. At some sites where numerous birds are detected, more intensive techniques may be required to accurately access the number of calling birds.

Wetland Transects

We suspect that many Australasian Bitterns do not breed if conditions are not suitable. Non breeding birds would appear not to call, so the best way of detecting them is by walking through or around the wetland to try to flush the birds.

We are currently going through Atlas data to identify sites where Bitterns have been recorded. If these sites have water, we would like them to be surveyed this spring/summer using the two survey methods outlined.  If you have a local wetland that you are able to survey, please contact us and we will send you a survey package. We will also be contacting observers living near potential sites to ask them to assist us with this survey.

Australasian Bitterns in Western Australia

The Australasian Bittern has a fairly restricted range in Western Australia, with most records centred in four main areas: the Swan Coastal Plain, Manjimup wetlands, and two sections of the South Coast (between Augusta and Bremer Bay, and from Esperance to Cape Arid). However, during the non-breeding period, they may occur at other wetlands where the key requirements of food and shelter are met.

The population of Australasian Bitterns has been declining in Western Australia since at least the 1980s, mainly due to loss of habitat through changes to the water conditions through different drainage regimes and land use, and changes to the chemistry of the wetlands, such as salinisation and eutrophication.

The Australasian Bittern Project in Western Australia was established in 2007 to work in concert with the national Birds Australia Bittern Survey. Work currently undertaken by the Australasian Bittern Project in Western Australia includes:
•    conducting bittern surveys;
•    reviewing wetland chemistry data;
•    documenting wetland characteristics;
•    raising awareness and engaging local communities; and
•    recording bittern calls to determine whether individual birds can be identified on the basis of their calls.

Contacts

South-east Australia - This e-mail address is being protected from spambots. You need JavaScript enabled to view it 03 9347 0757
Western Australia - This e-mail address is being protected from spambots. You need JavaScript enabled to view it 08 9312 1671

Downloads

Little Bittern call (mp3) recorded by Marjorie Paul near Nathalia VIC
Australasian Bittern call (mp3) recorded by Andrew Corrick near Casterton VIC and Roger Jaensch at Lake Pleasant View WA

Bittern Survey Form
Bittern Survey Guide

Australasian Little Bittern ID Kit
Australasian Bittern ID Kit

Bittern Chronicle September 2011
Bittern Chronicle August 2010
Bittern Chronicle August 2009
WABN Bittern Article June 2008