Data Zone
Justification of Red List category
This species has a small population size of c.1,100 mature individuals with less than 250 estimated to be in each subpopulation, and is undergoing a continuing decline as a result of large-scale and frequent fires. For these reasons, the species is classified as Endangered.
Population justification
Based on population densities at eight sites, Noske (1992) estimated the population at 50,000 individuals (14,000–182,000), while Woinarski (1992) estimated a much lower total of 5,000–10,000 individuals. Given the fire history of the species's range (it is dependent on large unburnt spinifex patches), Garnett et al. (2010) thought the population had declined to no more than 10,000 mature individuals; these estimations of distribution and abundance based on fire history afterwards proved accurate (Woinarski et al. 2012, NESP TSRH 2019). Based on more recent surveys and an evaluation of fire patterns, the population is re-estimated at 900-2,000 mature individuals (Einoder et al. 2021), with a best estimate of 1,100 following NESP TSRH (2019). Fire is thought to have substantially fragmented the range with what was once a formerly panmictic population now probably divided into more than 10 subpopulations, each with no more than 100 mature individuals (Einoder et al. 2021).
Trend justification
The species is inferred to be declining based on declining reporting rates, although there are some uncertainties with the trend. In Birdata (BirdLife Australia 2020), there were 24 records from 2000–2009 and three from 2010–2019. Of all complete eBird checklists (eBird 2021) from accessible suitable habitat in western Arnhem Land, 24% of the 80 before 2000 included the species, but only 18% of 89 for 2000–2009 and 3.3% of 271 for 2010–2019 (Einoder et al. 2021). In Kakadu, numbers in systematic replicated surveys at the same locations declined from a mean of 0.08 individuals/quadrat in 2001–2004 (recorded in 6/142 quadrats) to zero in 2010, although subsequent targeted searches in 2011 found 30 birds at 11 sites at 4/16 locations searched (93 hours, 139 km, Mahney et al. 2011). In Djelk IPA, no birds were found in the vicinity of a 1996 record; while one female Elder at Kolorbidadah outstation recognised the bird but had not seen it for at least 20 years. No one spending time in the rock country camping, hunting and fishing recognised the bird at all and birdwatchers now see the bird only rarely. The primary threat to this species is large-scale and frequent fire which is likely to be exacerbated by ongoing climate change (Garnett et al. 2013, Einoder et al. 2021).
Amytornis woodwardi is endemic to the Northern Territory, Australia. The species appears to be confined to the Arnhem Land plateau and escarpment, including the sandstone country of eastern Kakadu, Warddeken Indigenous Protected Area (IPA) and possibly Djelk IPA (NESP TSRH 2019). They may once have occurred in Nitmiluk National Park (J. McKean in Noske 1992), but there are no recent records.
White-throated Grasswrens live in mature spinifex Triodia spp. on bare flat plateaux and stepped or terraced hillsides along broad valleys, with or without narrow rocky gullies (Schodde and Mason 1975, Noske 1992), sometimes with open shrubland or woodland overstorey. They eat invertebrates, seeds and other vegetable matter and defend a territory of about 10 ha in which they build a domed nest within spinifex, usually laying two eggs (Noske 1992).
The primary threat is large-scale and frequent fire (Woinarski 2007) which is likely to be exacerbated by climate change (Garnett et al. 2013). Despite its rocky habitat offering protection from fires (Noske 1992), many fires are too hot and extensive to leave functional unburned refugia (NESP TSRH 2019). Fire regime may be improving. The size and frequency of fire in the Wardekken IPA has declined dramatically in the last two decades as a result of revitalised Indigenous burning (Ansell et al. 2020), protecting vulnerable ecosystems (Murphy et al. 2015). Fire management remained problematic in Kakadu National Park up to 2016 (Russell-Smith et al. 2017); since then a strategic burning program in Kakadu National Park has decreased the scale and intensity of fire in the stone country areas of the park (Director of National Parks unpublished, in Einoder et al. 2021). Other potential threats are predation by cats Felis catus and black rats Rattus rattus, although their impact on this species is yet to be studied or quantified (NESP TSRH 2019).
Conservation Actions Underway
Very limited baseline surveys have been completed. About 35% of the species's range is contained within Kakadu and Nitmiluk National Parks and most of the rest in the recently established Warddeken Indigenous Protected Area. The species formerly occurred in Nitmiluk National Park (contiguous with Kakadu), but there have been no recent sightings (and little sampling) there. It is listed as threatened under appropriate legislation, including as a National Threatened Species Strategy priority. Active fire management is producing fire regimes likely to be favourable to the species, at least in part of range.
Conservation Actions Proposed
Repeat past surveys at known sites and establish a more robust monitoring programme that is capable of detecting future declines. At known sites, determine the fire history, and make recommendations on appropriate conservation management. Undertake research to better understand key habitat and other requirements in relation to fire regimes and fire management options (J. Woinarski in litt. 2016). Determine the extent of movement between populations, using banding and genetic analysis. Document recovery time before spinifex can be reoccupied. Continue intensive fire management of Kakadu National Park and promote and support traditional fire management throughout western Arnhem Land.
20-22 cm. Robust, long-tailed, black, white and chestnut ground bird. Black top and sides of head and neck to mantle, with bold white streaks. Chestnut back and rump. Black wings and tail with chestnut edges to feathers. White lores, throat and upper breast. Black gorget on lower breast streaked white. Black sub-moustachial stripe joins breast gorget. Orange-buff belly in male. Sexes similar, but female is darker chestnut, especially on belly and flanks. Juvenile duller, streaking less distinct. Voice Rich, liquid trill. Buzzing contact calls. Hints Hops or scuttles rat-like between rocks and clumps of vegetation.
Text account compilers
Garnett, S., Berryman, A., Vine, J., Symes, A., Allinson, T
Contributors
Watson, C. & Woinarski, J.C.Z.
Recommended citation
BirdLife International (2024) Species factsheet: White-throated Grasswren Amytornis woodwardi. Downloaded from
https://datazone.birdlife.org/species/factsheet/white-throated-grasswren-amytornis-woodwardi 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.