Mallee emu-wren Stipiturus mallee

Transcription

1 COMPLETE CASE STUDY TRENDS IN SIGNIFICANT SPECIES AND COMMUNITIES - SOUTH AUSTRALIA Mallee emu-wren Stipiturus mallee Description The mallee emu-wren is one of Australia s smallest birds, weighing around 6 grams. The name emu-wren comes from its distinctive tail, which consists of long, filamentous feathers similar to emu feathers. Male mallee emu-wrens have a sky-blue face, throat and breast, while the females are quite plain. They form breeding pairs, but are also frequently seen in small groups, which suggests that co-operative breeding may occur. Mallee emuwrens nest in Triodia (porcupine grass) tussocks or dense shrubs. They feed mainly on invertebrates, foraging amongst low shrubs and on the ground. Mallee emu-wrens inhabit heaths and mallee-triodia systems in the semi-arid Murray Mallee region that straddles the South Australia/Victoria border. Triodia is an important habitat component, although the species can also use heaths without Triodia, providing they are structurally similar. The mallee emu-wren currently occurs in several disjunct populations, its former range having been fragmented by vegetation clearance and pastoral grazing. Within this fragmented distribution, fire is considered the main threat to this species persistence. In addition, recent declines during the current drought have elevated the risk of extinction of some small and isolated local populations. The population in South Australia is now likely to be less than 100 birds and is possibly restricted to Ngarkat Conservation Park. A small population in Billiatt Conservation Park has not been confirmed since Less is known about the Victorian population, but recent surveys (Clarke and Brown 2007) identified only four broad areas containing populations. The number of records in Hattah-Kulkyne National Park suggests this area may support the largest remaining local population, but the Murray-Sunset National Park is yet to be adequately surveyed and is likely to contain the largest areas of potential habitat (Clarke and Brown 2007). The species status in the Big Desert Complex needs clarification, though much of the area was burnt in Significance The mallee emu-wren was listed as Endangered under the Environment Protection and Biodiversity Conservation Act (EPBC) 1999 in September It is listed as Vulnerable in South Australia (National Parks and Wildlife Act 1972). In Victoria it is listed as threatened (Flora and Fauna Guarantee Act 1988) and classified as Vulnerable on the Advisory List of Threatened Vertebrate Fauna in Victoria (2003).

2 Data and information The populations of mallee emu-wrens in Ngarkat Conservation Park, South Australia, are now well documented. A long-term monitoring program has recorded trends since 1990 using permanent transects surveyed biannually (Paton and Rogers 2007). The Department for Environment and Heritage (DEH) conducted intensive population surveys in this reserve during 2005 and DEH also conducted surveys of Billiatt Conservation Park in 2003 and 2004 (Gates 2003, 2005), and follow up searches of known mallee emu-wren locations in this reserve were conducted in 2005/06. In Victoria, surveys were conducted around Nowingi in 2005 (Smales et al 2005), and the Department of Sustainability and Environment (DSE) commissioned surveys across the species former range in 2006 (Clarke and Brown 2007). Intensive surveys to determine species density have occurred in Hattah-Kulkyne National Park, as part of a doctoral thesis (S. Brown pers. comm.). Additional records generated from a tri-state research program on fire ecology, conducted by Deakin and La Trobe Universities, were compiled in the DSE survey report (Clarke and Brown 2007). Ecological research on mallee emu-wrens has begun only recently. Smith (2004) investigated the species habitat requirements at Ngarkat Conservation Park, and this was followed by attempts to create a habitat suitability model across their range (Clarke 2005). A doctoral student is studying aspects of the mallee emu-wren s ecology and population structure in Hattah-Kulkyne National Park, Victoria (S. Brown pers. comm.). Long term changes in the vegetation communities in Ngarkat Conservation Park have been studied by Associate Professor David Paton, Adelaide University. This research indicates that interactions between fire and drought have brought about declines in habitat suitability for fauna, including mallee emu-wrens. Management requirements and issues Wildfires ignited by summer lightning strikes are common in the mallee region and are a natural part of the system. The mallee vegetation has adapted to fire and is dependent on fire for regeneration in its absence these communities eventually senesce, with potentially permanent changes in diversity and structure. Prior to broad-scale land clearance, bushfires did not represent a severe threat to birds such as mallee emu-wrens. Although fires would have resulted in the loss of local populations, these losses were temporary; when the habitat recovered, birds from adjacent unburnt areas recolonised the area. However, vegetation clearance and probably also pastoral grazing have permanently fragmented the habitat, creating isolated patches. In these new landscapes the natural fire regime has caused the complete loss of habitat patches resulting in local extinctions of mallee emu-wrens, or substantial reductions in patch size and consequently population size. Isolation has reduced or prevented recolonisation, resulting in declines in the total population. 2 ASSESSMENT OF AUSTRALIA S TERRESTRIAL BIODIVERSITY 2008

3 Likewise, a lack of fire in some areas of this altered landscape has been associated with the long-term decline of mallee emu-wrens, with birds gradually disappearing from some long-unburnt areas. The lack of renewal of Triodia and other components of the vegetation causes a decline in habitat suitability and the consequent loss of Emu-wrens from localised areas. When this happens in an isolated patch, it results in a local extinction. Drought, another natural process, has also been implicated in this species decline (Paton 2000, Paton and Rogers 2007). Evidence from both the Ngarkat and Hattah surveys suggest that drought conditions increase adult mortality, and probably also reduce breeding productivity. Although population fluctuations with drought are normal, the small and isolated nature of current populations means that these declines represent a substantial increase to the risk of local extinctions. Drought also interacts with fire, affecting the regeneration and productivity of vegetation communities. For example, vegetation recovering from a 1990 fire in Ngarkat Conservation Park took only five years to resemble the pre-fire state, while an area burnt in 1999 still had not recovered to that extent after eight years of drought conditions following the fire (Paton and Rogers 2007). Further, the survival patterns of some important plant species indicate this habitat may not return to the same structural diversity as its pre-fire state. Such altered states reduce the carrying capacity of the habitat. To return to the pre-fire state, the vegetation will likely require another fire followed by several years of good rainfall. It is likely that mallee emu-wrens now occupy most of the currently available habitat in South Australia. It will be years before most of the recent fire scars provide suitable habitat again, especially if rainfall levels remain low. Therefore, another issue faced in managing this species is a slow rate of population recovery due to this resource limitation and the reduced number and distribution of extant populations. Management actions and responses The South Australian Department for Environment and Heritage employed a two person team in 2005 to run a Threatened Mallee Birds program, with the mallee emu-wren as a target species. This team has focused on determining distribution and population sizes, and has also commenced active management in collaboration with DEH fire managers, to protect remaining populations from bushfires. The following advances toward the recovery of the mallee emu-wren in South Australia have been achieved: A thorough literature review, compiling all information into a species profile A review of historical texts to ascertain the former distribution of the species, and the generation of GIS-based distributional data for South Australia ASSESSMENT OF AUSTRALIA S TERRESTRIAL BIODIVERSITY

4 Systematic searches of likely habitat across the region, and the identification 5-6 local populations in Ngarkat Conservation Park area. A population census at these sites in Assessment of the impacts of the January 2006 fire, which burnt a large area of habitat and caused the loss of two local populations. Development of Fire Management Plans for the Ngarkat and Billiatt districts, addressing the conservation requirements of mallee emu-wrens. Prescribed burns were completed in Ngarkat Conservation Park, designed to protect the largest population and its habitat from bushfires. The remaining Ngarkat populations were re-surveyed in An assessment of long-term survey data and measures of habitat change to identify conservation concerns and management options was completed (Paton and Rogers 2007). Surveys commenced in two habitat types to build on the habitat suitability model developed by Smith (2004). Discussions initiated to develop a co-ordinated management response between South Australia and Victoria, and the establishment of a National Recovery Team. Outcomes It is early days yet for the recovery of the mallee emu-wren, but awareness and recognition of this species as a conservation concern is increasing. Recent data show the population to still be in decline. Some of this decline is likely to be natural variation due to drought, from which the population would usually recover. However numbers are now so low that any losses could be devastating to the species long-term persistence. Substantial progress has been made in our understanding of the issues impacting on the mallee emu-wren and its habitat and this will allow for the development of sensible strategies for the species recovery. Strategic prescribed burning had achieved some level of protection from bushfire for the extant South Australian population. However, the effectiveness of these actions is unknown, due to the uncertainty associated with natural fires. Nevertheless, the mallee emu-wren is now acknowledged as an important issue in fire management throughout its South Australian range, and its requirements are addressed in long-term fire management plans for the region. Communication and collaboration between South Australia and Victoria with respect to the management of mallee-dependent species is improving. This will lead to better, integrated management across the region for many species including the mallee emu-wren. 4 ASSESSMENT OF AUSTRALIA S TERRESTRIAL BIODIVERSITY 2008

5 Future scenario Stabilising existing populations and protecting habitat recovering from fire should be the initial goals for the management of this species. Also, the Victorian distribution and population size should be clarified to enable an informed assessment of management options. Some management scenarios include: translocation of birds to isolated habitat to simulate natural recolonisation processes, a captive breeding program, and managing vegetation through ecological burning to shift degraded states toward more productive habitat. Translocation and captive breeding involve the removal of birds from extant populations, which can be a risk to the parent population and the species long-term persistence. Therefore, these actions require a good understanding of the capacity of local populations to provide a source of birds. Baseline information is still needed for this species (e.g. breeding productivity data and resource requirements within different systems), which would allow us to monitor recovery efforts and better predict the outcomes of particular actions. The establishment of a monitoring program across the species range that will assess existing populations and the recovery of potentially new populations is also a high priority. Mallee emu-wrens represent a group of species that are dependent on the Murray Mallee a system that requires effective cooperation between neighbouring states for its management. Improving the prospects of recovery for this species will improve our understanding and management of this system leading to greater security for this mallee community. ASSESSMENT OF AUSTRALIA S TERRESTRIAL BIODIVERSITY

6 Figure 1. Population distribution map for mallee emu-wrens Mallee Emu-wren. Photo Lynn Pedler 6 ASSESSMENT OF AUSTRALIA S TERRESTRIAL BIODIVERSITY 2008

7 References Clarke RH (2005). Ecological requirements of birds specialising in mallee habitats. Report to Department of Environment and Heritage. La Trobe University, Adelaide. Clarke RH and Brown S (2007). The mallee emu-wren in Victoria: recent surveys and an assessment of habitat preferences and population densities. Report to the Department of Sustainability and Environment. School of Life and Environmental Sciences, Deakin University, Melbourne. Gates J (2003). Ecology of Threatened Mallee Birds in Billiatt Conservation Park Baseline Distribution and Abundance Surveys, Unpublished report to the Wildlife Conservation Fund, Adelaide. Gates J (2005). Distribution of Threatened Mallee Birds in Billiatt Conservation Park 2004 Survey Results. Report to the Wildlife Advisory Committee. Department for Environment and Heritage. Murraylands Region, South Australia. Paton DC (2000). Biotic responses to fire and drought and developing a fire management strategy for Ngarkat Conservation Park: the importance of site fidelity and hot spots for biodiversity conservation. Report to the Department for Environment and Heritage. School of Earth & Environmental Sciences, University of Adelaide, Adelaide. Paton DC and Rogers DJ (2007). Status of Mallee Emu-wrens (Stipiturus mallee) in the Ngarkat complex of parks. Report to Wildlife Conservation Fund, Project # School of Earth and Environmental Sciences, University of Adelaide, Adelaide. Smales I. Koehler S, Miller J, and Harrington R. (2005). Survey for Mallee Emu-wren Stipiturus mallee in the region of the Long Term Containment Facility study area, Nowingi, Victoria. Report to Major Projects Victoria, Project Biosis Research, Victoria. Smith G (2004). Distribution and Habitat Requirements of Mallee Emu-wren (Stipiturus mallee) within the 1990 fire scar of Ngarkat Conservation Park: Towards a habitat suitability model. Honours Thesis. University of Adelaide, Adelaide. ASSESSMENT OF AUSTRALIA S TERRESTRIAL BIODIVERSITY