Data Zone
Justification of Red List category
This species has a population size of less than 10,000 mature individuals, with the largest probably containing only marginally more than 1,000. Given many subpopulations are inferred to be declining as a result of both natural and human-mediated fires, the species is currently believed to be at a moderate risk of extinction. As a result, it is listed as Near Threatened, but it should be closely monitored whether the larger subpopulations continue to decline.
Population justification
There were estimated to be about 5,000 A. m. merrotsyi in 2004 (Carpenter 2004) but the habitat of what was the largest subpopulation, around Stokes Hill in the south-east of Ikara-Flinders Ranges National Park, may no longer support 1,000 pairs (Carpenter 2004) because it has been degraded and there has been a significant reduction in the number of sightings in this area (Black and Gower 2017, A. B. Black in litt. 2021). Consequently, this subpopulation may now approach c.1,000 mature individuals in total (Carpenter et al. 2021a) and is placed in the range 1,001-1,500 mature individuals. Another 3,000 mature individuals are assumed to be spread among the other three subpopulations (Carpenter 2004). The population of A. m. pedleri was estimated in 2009 to be 300 birds at Paney Station in Gawler Ranges National Park, 200 each at Mt Ive Station and Hiltaba Nature Reserve and 50 at each of the four less important sites (G. Carpenter, A. B. Black unpublished, in Carpenter et al. 2021b) and is thought to be little changed. The global population size is therefore best estimated at c. 5,000 mature individuals, placed here in the range 4,000-6,000.
Trend justification
Trends of A. m. merrotsyi are highly uncertain as there have been no recent surveys, but birdwatchers have been unable to find any at many former locations (G. Carpenter unpublished, in Carpenter et al. 2021a). The population of A. m. pedleri is thought to be stable, although the subspecies is thought to comprise less than 20% of the total population. In 2005, A. m. pedleri occurred at 19/51 sites surveyed on Hiltaba and Kolendo Stations; in 2017, despite very dry conditions, they were present at 20/57 sites, of which 40% were on Hiltaba. Even though they were absent from 11 previously occupied sites in an area of about 100 km2 on Gawler Ranges National Park that was burnt in 2011, they were expected to return given the recovery of vegetation (SA AL NRMB 2018). Overall, a continuing decline in mature individuals is inferred based on evidence of the ongoing threats to the species and the lack of sightings at sites where the species has previously occurred (Carpenter et al. 2021a).
This species is endemic to Australia, where it is patchily distributed in southern South Australia. A. m. merrotsyi occurs in four subpopulations: between Dutchman's Stern and Buckaringa north of Quorn; in the Black Range east of Hawker; in and adjacent to the south-east corner of Ikara-Flinders Ranges National Park; and from about Italowie Gorge north through Vulkathunha-Gammon Ranges National Park to Mount Freeling in the north (Christidis et al. 2008, Black and Gower 2017). A fifth more southerly population at Telowie Gorge near Nelshaby was last recorded in 1981 and is thought to have been extirpated (Parker 1982). There are also unconfirmed sightings from the Horseshoe Range and near Saltia, east and west of Quorn respectively (Black and Gower 2017) and the Elder Range west of Hawker (B Williams pers. comm., in Carpenter et al. 2021a) In the last ten years, there have been only two records from the Dutchman's Stern population and one from the Black Range (BirdLife Australia 2020, eBird 2021, A. B. Black unpublished, in Carpenter et al. 2021a). A. m. pedleri occur in the central and western Gawler Ranges, (Christidis et al. 2008, Black and Gower 2017), where there are three main subpopulations: the eastern side of Mt Ive Station, the eastern side of Paney Station in Gawler Ranges National Park and on Hiltaba Reserve. Smaller areas of occupied habitat occur between Thurlga homestead and Lake Gairdner and at two sites between the Paney and Hiltaba locations (Black and Gower 2017).
A. m. merrotsyi inhabit rocky hillsides and gullies, stony rises and ridge-crests covered with mature spinifex Triodia spp. grassland, usually with scattered low shrubs and an open overstorey of low trees (Christidis et al. 2008). They reach peak densities 10–30 years after fire but will recolonise patches 5–7 years after a fire if the spinifex has recovered (G. Carpenter unpublished, in Carpenter et al. 2021a). A. m. pedleri live on rocky granitic hilltops, ridges and hillsides covered with spinifex Triodia tussock grassland and usually with scattered spiny shrubs (Christidis et al. 2008); in a survey in 2017, 75% of sites where grasswrens were detected had ≥20 % cover of spinifex >25 cm in height compared to only 38% of sites where grasswrens were not detected (SA AL NRMB 2018). Both subspecies forage mostly on the ground, eating seeds, fruits, insects and other invertebrates and lay two eggs in a domed nest hidden in spinifex (Higgins et al. 2001),
The main threat to A. m. merrotsyi is fires that are too large or frequent (Higgins et al. 2001): several large fire events could eliminate entire subpopulations (G. Carpenter unpublished, in Carpenter et al. 2021a) and are only likely to become more frequent and severe given changes in fire risk brought on by increases in the frequency and intensity of droughts and heat waves (Clarke et al. 2016; Evans et al. 2017; Herold et al. 2018). Much of the region is burned on average every ten years, particularly for sheep grazing (Whisson 1999; Carpenter 2004), but feral goats Capra hircus (Agnew et al. 2010) and rabbits Oryctolagus cuniculus also damage habitat (Cooke 2014) and Stokes Hill has been overgrazed by euros Osphranter robustus (Black and Gower 2017). Predation by foxes Vulpes vulpes, may also be significant, given the comparatively high population densities of A. m. merrotsyi in the heavily baited south-east of Flinders Ranges National Park (Carpenter and Bellchambers 2003; Carpenter 2004). Grasswrens are also known to be taken by cats Felis catus (Woinarski et al. 2018). Fire is also the main threat to A. m. pedleri, both natural and human-mediated (Department of the Environment 2014), with fire burning most of Gawler Ranges National Park in 2011 (SA AL NRMB 2018). Predation and overgrazing are also significant threats to A. m. pedleri. Unlike in the Flinders Ranges, there is not a severe declining trend in rainfall.
Conservation Actions Underway
The Flinders Ranges and Gawler Ranges National Parks protect significant parts of the range. Three of the four A. m. merrotsyi subpopulations are partly in protected areas. The largest populations of A. m. pedleri are protected, one in a private reserve. Listed as threatened under appropriate legislation. Fox, cat and goat control has been undertaken.
Conservation Actions Proposed
Monitor population trends at key sites. Determine numbers and trajectories of all subpopulations, including the conditions needed to re-establish populations after fire. Survey for additional populations of A. m. pedleri on Noning, Siam and Yardea Stations and Hiltaba Nature Reserve. Research optimal fire regimes for the species. Assess the impact of predation by foxes. Assess if any threats are likely to cause declines, particularly grazing impacts on habitat and food availability. Understand the impact of drought. Actively manage fires to reduce overall extent and frequency. Manage fire to ensure areas of old spinifex remain in the landscape. Reduce grazing pressure by sheep, goats and euros where necessary. Continue fox control.
Text account compilers
Vine, J.
Contributors
Garnett, S., Black, A. & Carpenter, G.
Recommended citation
BirdLife International (2024) Species factsheet: Short-tailed Grasswren Amytornis merrotsyi. Downloaded from
https://datazone.birdlife.org/species/factsheet/short-tailed-grasswren-amytornis-merrotsyi on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.