Data Zone
Justification of Red List category
Recent monitoring data suggest rapid declines in one of the largest subpopulations at Barren Grounds/Budderoo due to unknown causes, and the subpopulation at Nadgee has also declined rapidly as a result of the severe bushfires in 2019-20. It is unclear whether these declines will continue, although some sites population are, for now at least, stable. The species is therefore listed as Vulnerable.
Population justification
The total population of D. b. brachypterus had previously been estimated at c.3,000 mature individuals (Bain et al. 2021), including 1,250 at Barren Grounds/Budderoo, 1,100 at Jervis Bay, 50 at Cataract, about ten at Red Rocks and 300 at Nadgee and Howe Flat (NESP TSRH 2019) with 140–160 birds at Howe Flat in 2020 (M. Bramwell unpublished; Clarke et al. 2020, Bain et al. 2021). An unknown number occur on the Beecroft Peninsula, but they are at all 40 monitoring sites established there (Lindenmayer et al. 2016). In 2020, 43 individual D. b. monoides were known to be alive in the wild, with another two sites having recent possible sightings, suggesting in total 45–46 birds were present (D. Charley unpublished, in Charley et al. 2021). Of these, four were confirmed in Queensland and 39 confirmed in NSW. The total number of D. b. monoides is therefore thought to be 25-40 mature individuals, with a best estimate of 30 (Charley et al. 2021). However, rapid declines in some populations have rendered some of these estimates no longer appropriate. Given a suspected decline of 30–49% of D. b. brachypterus reported at Barren Grounds/Budderoo and Nadgee/Howe Flat (but population stability at at least some other sites), the global population size is revised to 1,500-2,100 mature individuals, with a best estimate of 1,800.
Trend justification
Until recently, the population of D. b. brachypterus at Nadgee had increased steadily to about 400 (NESP TSRH 2019) before fire in 2020 burnt most of the suitable habitat (Oliver & Malolakis 2020). Based on initial assumptions about mortality at different severity classes (severity low: 20%; medium: 50%; high: 100%; very high: 100%) and maps of fire severity, the fires killed an estimated 9% of the total population of D. b. brachypterus with estimates ranging from 5% to 11%, depending on the fire-related mortality assumptions adopted (G. Ehmke, S.T. Garnett unpublished, in Bain et al. 2021). Taken alone, the Nadgee population alone declined by 81% in one year (D. Bain in litt. 2022). Elsewhere in New South Wales, annual monitoring demonstrated steady increases at Cataract and Budderoo, probable increases at Beecroft Peninsula, stability at Jervis Bay and fluctuations at Barren Grounds (NSW OEH 2018, 2019). However, recent monitoring data suggest that these fluctuations at Barren Grounds/Budderoo are actually a decline: over the past three generations (12.9 years; Bird et al. 2020), the population has apparently declined by 78% from unknown causes (the area was not burned) (D. Bain in litt. 2022). This is equivalent to a loss of approximately 1,000 birds and is thought to have caused a c.32% decline in the global population if all other sites remained stable. Average densities of bristlebirds detected along transects in Booderee National Park during annual spring surveys since 2015 have been fairly constant across years, though with a sharp drop in 2018 followed by the highest density so far recorded in 2019 (Director of National Parks unpublished, in Bain et al. 2021). At Beecroft Peninsula, they were detected 337 times on 152 surveys, at least twice the detection rate of any other species except New Holland Honeyeaters Phylidonyris novaehollandiae, with effects of bombardment during military training having no impact on detection frequency (Lindenmayer et al. 2016). In Victoria, numbers at Howe Flat in 2008 (120–160; Bramwell 2008) differed little from those in 2020. Taking into account the losses in Nadgee following the severe 2019-20 bushfires and the reported declines from Barren Grounds/Budderoo, the total decline of D. b. brachypterus over the past three generations could be as high as 39–43%.
Numbers of D. b. monoides have been stable or slightly increasing in the last decade: in 2014, 11 birds were recorded, suggesting 13–30 birds present; in 2016, 18 birds were recorded (suggesting 20–30 birds present; NESP TSRH 2019); and in 2018, 25 birds were recorded suggesting 30–40 birds were present (D. Charley unpublished, in Charley et al. 2021). However, this was preceded by a long history of attrition: in 1988, 154 individuals were located in 103 territories; in 1996, there were 36 birds in 30 territories; in 1997–1998, there were 26 birds in 16 territories; and, in 2010, there were 25–30 individuals (Garnett et al. 2011).
Overall, the population is therefore suspected to have declined 30–49% over the past three generations based on the assumption that some unmonitored sites have remained stable. The principal cause of declines at Barren Grounds/Budderoo has not been identified and whether it is likely to continue in the future, or affect other sites (at least some of which have populations that have remained stable in the same time window) is wholly unknown.
Dasyornis brachypterus is endemic to Australia. D. b. brachypterus occurs in Victoria at Howe Flat in Croajingolong National Park, in southern New South Wales at Nadgee Nature Reserve and in central coastal New South Wales at Barren Grounds Nature Reserve, Budderoo National Park, the Jervis Bay area, near Cataract Dam and at Red Rock Nature Reserve (Baker 1997, 1998; Bramwell 2008, NSW OEH 2012, BirdLife Australia 2020). Subpopulations on Beecroft Peninsula, and Cataract on the Woronora Plateau, were reintroduced for conservation purposes (Baker et al. 2012). Fires in 2019–2020 burnt 15% of all 1x1 km squares from which birds have been recorded since 1990 (G. Ehmke unpublished, in Bain et al. 2021) with <10% of the habitat remaining at Nadgee (Oliver & Malolakis 2020). D. b. monoides are confined to the hinterland of coastal south-east Queensland and north-east New South Wales. In Queensland, they are currently known from one site near Mt Gipps on the Queensland/New South Wales border and possibly one at Mt Barney (Department of Environment and Science 2018). In New South Wales, they occur at several sites near Kyogle in the Border Ranges (NESP TSRH 2019). They are presumed to have been extirpated from Conondale Ranges, the Stretcher Track, Razorback Mountains, Mt Burrell, Big Scrub, Mt Richmond, the Dorrigo Plateau and probably Spicer's Gap; in none of these areas have there been confirmed records for over a decade despite searching. Fires in 2019–2020, initially thought to have burnt out some subpopulations, missed all of them with the exception of the possible Mt Barney subpopulation (D. Charley unpublished, in Charley et al. 2021).
D. b. brachypterus inhabits dense, low heathland, sedgeland and swamp communities but also occur in open sclerophyll woodland or forest with an understorey of shrubs and a dense ground layer of grasses or bracken Pteridium esculentum. They are eliminated by severe fire but can recolonise recently burnt areas if there are adequate nearby unburned refuges (Bain et al. 2008, Lindenmayer et al. 2009). Population density increases until at least a decade after fire (Baker 2001, Bain and McPhee 2005), but habitat suitability is influenced by long-term successional changes in vegetation communities which is not simply a function of time since fire (Lindenmayer et al. 2016, Foster et al. 2017). They feed on small invertebrates, seeds and small fruits (Gibson & Baker 2004) and usually lay two eggs in a hidden domed nest built low in dense vegetation (Higgins and Peter 2002). D. b. monoides occurs in open eucalypt forests or woodlands on highly fertile volcanic soils in a region with high rainfall and warm summers. Although they are always close to rainforest, they require an understorey dominated by large patches of diverse, tall, thick grass, a habitat rapidly replaced by woody shrubs, rainforest understorey trees and weeds unless burnt frequently by low-intensity fires (Holmes 1989; Rohweder 2000; Rennison 2016; Stone et al. 2018, 2019). They have also been recorded in montane heath on Mount Barney and in sedges and mat-rushes along watercourses on the Dorrigo Plateau (Holmes 1989). They feed on or near the ground on small invertebrates, seeds and small fruits (Gibson & Baker 2004), with invertebrate numbers and nutritional quality being highest in the dense grass near rainforest that they favour (Stone et al. 2019). They lay two eggs, but rarely raise more than one fledgling, in a domed nest set in the crown of a tussock grass under a canopy gap (Higgins and Peter 2002, D. Charley unpublished, in Charley et al. 2021) with canopy gaps appearing to be an essential nesting habitat requirement (D. Charley unpublished, in Charley et al. 2021).
Extensive fire is the main threat to D. b. brachypterus (NSW OEH 2012, NESP TSRH 2019), extirpating the subspecies from 10/11 known locations in Victoria from 1978–1994 (Clarke & Bramwell 1998), and severely affecting subpopulations at Barren Grounds in 1968 and Nadgee in 1980 (Baker 1998) and 2020 (Oliver & Malolakis 2020). Most historic sites in Victoria that no longer support birds were again affected by fire in 2020. Although the overall risk from fire is now reduced because of the increase in the number of subpopulations, extreme fire weather is likely to increase in frequency (Di Virgilio et al. 2019, Dowdy et al. 2019) driven by increases in the frequency and severity of drought and heat waves (Evans et al. 2017, Herold et al. 2018). Most heath is floristically intact, and the removal of bitou bush Chrysanthemoides monilifera, increasing habitat quality, has assisted bristlebirds at one site (Lindenmayer et al. 2017). Historically clearance for agriculture and fire are assumed to have extirpated populations north of Sydney (NSW OEH 2012). Changes in rainfall patterns and sea-level rise may impact on the wetland complex of Howe Flat where the bird is dependent on riparian scrub vegetation, often less than 5 m in elevation (M. D. Bramwell unpublished, in Bain et al. 2021). The main current threat to D. b. monoides is a change in fire regime, particularly a regime in which fire is insufficiently frequent to maintain a dense grass sward, and from the isolation and small size of the remaining severely fragmented habitat patches, a legacy of historical land clearance (Rennison 2016; Stone et al. 2018, 2019). However, major wildfire can sometimes eliminate particularly isolated populations and excessively frequent fires can eliminate tussocks which are then replaced with blady grass Imperata cylindrica or weeds. Heavy grazing has the same effect, but there is little grazing in remaining occupied locations. Predation by foxes Vulpes vulpes and cats Felis catus may be a threat, given the scarcity of the birds and their ground-dwelling habit, as may natural nest predators, such as Pied Currawongs Strepera graculina and native small mammals such as the bush rat Rattus fuscipes (NSW OEH 2012, Department of Environment and Science 2018, Charley et al. 2021). Climate change, particularly increases in the frequency and intensity of drought (Evans et al. 2017) and heat waves (Herold et al. 2018), may also be placing increasing pressure on the birds and their prey. There are also concerns that such a small population must be, or will soon become, genetically depauperate (Stone 2018). Intriguingly, the most recent declines seen at Barren Grounds have occurred in spite of fire (D. Bains in litt. 2022) and the cause remains unidentified.
Predation by foxes Vulpes vulpes (Lindenmayer et al. 2009), and possibly cats Felis catus (Woinarski et al. 2017), especially predation following fire (Lindenmayer et al. 2018, N. Dexter unpublished, in Bain et al. 2021), is also thought to be significant but bristlebird populations at Budderoo and Cataract had been increasing despite the presence of both (NSW OEH 2019).
Conservation Actions Underway
D. b. brachypterus: Almost the entire population is within protected areas. Listed as threatened under appropriate legislation, including as a National Threatened Species Strategy priority. The three main southern populations in New South Wales (Barren Ground-Budderoo, Jervis Bay-Booderee and Nadgee Nature Reserve) have undergone surveys and initial ecological research. Habitat mapping has been conducted at Jervis Bay. Research has been conducted over three years into the ecology and translocation of 50 birds from Bhewerre Peninsula to Beecroft Peninsula in the Jervis Bay region, including habitat selection by the species after fire. A second translocation of approximately 50 birds from Barren Grounds Nature Reserve to Sydney Catchment Authority (SCA) lands has been undertaken. Other fire ecology research has been conducted. Research on the southern population has shown that not all habitat needs to be constantly maintained as greater than 14 years unburnt, as long as large, adjacent and long unburnt (for over 20 years) areas are protected for emigration from and recolonisation of more recently burnt areas (Bain et al. 2008, Lindenmayer et al. 2009). Annual monitoring is carried out at Jervis Bay National Park, Barren Grounds Nature Reserve and Nadgee Nature Reserve. At Nadgee, habitat monitoring is conducted every two years. Fox control is carried out for the Jervis Bay-Booderee and Barren Grounds-Budderoo populations. Weed control, particularly of Bitou Bush has been undertaken at Booderee National Park, though recent studies have shown that the species can utilise Bitou Bush as post-fire refugia. The vegetation where the northern population can be found is currently being investigated as to how it interacts with fire. Results indicate that most areas need to be burnt on a 4 – 5 year cycle to maintain a healthy understory (D. Stewart in litt. 2016). In response to the Australian Black Summer bushfires, emergency conservation intervention was implemented where birds were captured from Cape Howe to establish an ex situ insurance population; birds were re-released to the wild within 2 months once the fires had ceased (Selwood et al. 2022).
D. b. monoides: Some birds in public and private protected areas. Listed as threatened under appropriate legislation, including as a National Threatened Species Strategy priority. Fences and fire-breaks have been constructed. Research into preferred fire regimes is being completed in 2016 and results indicated a requirement for a frequent fire regime with interfire intervals of 3-6 years (Tasker and Watson pers. comm. 2016). Integrated fire and weed management is being implemented on key NSW sites. Some pig and cat control is undertaken. Vegetation monitoring sites are being established. The majority of the territories in the northern population have been mapped. Current efforts to locate occupied sites include using trained dogs in SE Queensland and NE New South Wales (I. Gynther in litt. 2016). Subpopulations regularly monitored, particularly after habitat management works and fire. The population is now the focus of an intense captive breeding programme with the aim of re-establishing the species at several sites.
Conservation Actions Proposed
D. b. brachypterus: Continue to monitor the density of the species in long unburnt habitat and study the relationship between the species and the post-fire age of habitat (OEH 2012). Develop contingency plans for fire. Assess the need for the genetic rescue of southern populations. Monitor populations annually. Monitor habitat every two years. Determine the conditions under which feral predator control is necessary. Encourage public participation and provide information. Minimise the loss of habitat on private land from future residential and commercial developments in the Jervis Bay area. Retain and manage known or potential habitat corridors between reserves (OEH 2012). Continue active management of fire in the habitat of remaining populations. Continue to expand the number of locations supporting bristlebird populations. Conduct ecologically sensitive hazard reduction burns at central populations (Barren Grounds-Budderoo and Jervis Bay-Booderee National Parks) to reduce the impacts of large intense fires.
D. b. monoides: Continue to survey for a new population in the vicinity where the species once occurred. Identify additional territories and potential habitat. Continue to monitor annually or biannually, involving landholders, feeding the information directly to managers. Release captive-bred birds into areas with small populations and where the species has been recently recorded. Investigate the fate of birds in supplemented populations. Determine how to improve breeding success in the captive population. Expand the capacity for captive breeding to allow releases at multiple sites. Judiciously augment the captive breeding population with birds from the southern subspecies. Improve connectivity of fragmented habitat patches where possible through targeted fire management and shrub/weed control. Manage fire at multiple sites in Queensland and New South Wales on both private and public lands.
Both subspecies: Determine a suitable fire management strategy. Continue studies on population genetics. Control weeds, foxes and cats.
18-22 cm. Medium-sized, sturdy, grey-brown passerine. Sexes similar, female slightly smaller. Dark cinnamon-brown upperparts. Rufous-brown upperwing and uppertail. Grey-brown underparts, faintly scalloped. Grey-brown sides of belly and flanks. Brown undertail-coverts. Dull rufous-brown undertail. Red iris. Juvenile, pale brown iris. Similar spp. Similar in jizz and skulking behaviour to Rufous Scrub-bird Atrichornis rufescens but lacks barring on upperparts. Voice Frequent, ringing contact call, loud, melodious song and chattering, staccato, squeaky notes.
Text account compilers
Vine, J., Berryman, A., Garnett, S.
Contributors
Bain, D., Baker, L., Gynther, I., Oliver, D. & Stewart, D.
Recommended citation
BirdLife International (2024) Species factsheet: Eastern Bristlebird Dasyornis brachypterus. Downloaded from
https://datazone.birdlife.org/species/factsheet/eastern-bristlebird-dasyornis-brachypterus on 23/11/2024.
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 23/11/2024.