Justification of Red List Category
This species has a very restricted range. Large fires since 2001 have substantially reduced the population in the past, and although there has been a slow increase in numbers in the last three generations, a continuing decline in habitat quality and mature individuals is projected in the next three generations as a result of fire. As a result, the species is classified as Endangered.
Noisy Scrub-bird numbers are currently about 1,380 mature individuals (Burbidge et al. 2018, Comer et al. 2020) based on a ratio of 2.5 individuals for each territorial male (Danks et al. 1996).
The population increased exponentially from about 1983 to 2001 but fires in that year, 2004 and 2015 severely reduced the population on each occasion: on the mainland, there were 569 singing males in 1999, 733 in 2001, 278 in 2005, 379 in 2011, about 520 in 2015 and 415 in 2019 (estimated 1037 mature individuals) (Comer 2002; Comer et al. 2005, 2020; Danks and Comer 2006; Burbidge et al. 2018). In 2019, there were 137 singing males on Bald Island (estimated 342 mature individuals) (Comer et al. 2020). Reasons for a 75% population decline on Mt Gardner since 1994 are not well understood, but the pattern is not correlated with territory size, marginal declines in rainfall or fire impacts (Roberts et al. 2020). Most of this decline has been in the last decade – 70% since 2011 (Comer et al. 2020). Overall, there has been a 28% decline since 2001 but in the last three generations monitoring indicates a change in trajectory with the population increasing by about 10%. There is a high probability, however, that fire will cause population declines in the next three generations based on the increasing frequency of droughts and heat waves in the region (Comer et al. 2021).
Atrichornis clamosus is found on the south coast of Western Australia, Australia, between Two Peoples Bay and Cheyne Beach, where natural spread from Mt Gardner, where rediscovered in 1961, has been augmented by translocations to Mt Manypeaks and the Mermaid area near Cheynes Beach. The species was also introduced to nearby Bald Island (Danks et al. 1996, Gilfillan et al. 2009, Burbidge et al. 2018). In the 19th century, birds were recorded from near Waroona, in the Margaret River-Augusta area and closer to Albany (Whittell 1943, Abbott 1999) but attempted reintroductions to the Darling Ranges, Porongurup National Park, Mt Taylor, Gull Rock and sites west of Albany have failed (Tiller 2009, Comer et al. 2010). The outcome of a recent trial translocation to Mondrain Island (Archipelago of the Recherche) is not yet known (S Comer unpublished).
Noisy Scrub-birds live in the shrub-layer and understorey of dense vegetation where sedges or piles of debris for nesting are interspersed with small open areas with a thick layer of leaf-litter where they forage for terrestrial arthropods (Danks 1991, Danks and Calver 1993, Danks et al. 1996). The female lays a single egg in a domed nest, which is usually built in a clump of sedge. Historically, the species may have occupied swamp vegetation within Jarrah Eucalyptus marginata and Marri E. calophylla forest (Smith 1985). Dispersing birds cross roads but not cleared land (Danks 1991).
The historical disappearance of the species from most of its former range has been attributed to changes in fire regime following the disruption of Aboriginal fire management before the 1880s. In 1976, the single, remnant population survived in an area protected from fire by the terrain. The frequent burning of swamps to make them more suitable for cattle-grazing, as well as their drainage and clearance for horticulture, would have had major impacts. Currently the major threat is from extensive, intense bushfires (Comer and Burbidge 2006, Danks and Comer 2006, Burbidge et al. 2018); habitat may take up to ten years to recover fully following fire (Danks and Comer 2006). In 1994, a fire at Mt Taylor destroyed most of a recently translocated population, with remaining birds disappearing within the subsequent year. The largest subpopulation was formerly on Mt Manypeaks, following a remarkable recovery since translocations began in 1983, however in summer 2004/2005, a fire there burnt a 4,500 ha block of habitat (Comer and Burbidge 2006), amounting to the loss of one third of the suitable habitat for the species in the Albany area (Danks and Comer 2006). Surveys in 2005 revealed a 55.6% reduction in the number of singing males in the Albany Management Zone compared to numbers in 2001, largely as a result of the loss of birds from within the burnt area at Mt Manypeaks (Danks and Comer 2006), with the loss of almost all of the birds (c.1,000) in the 427 territories counted in 2001 (Comer and Burbidge 2006). Post-fire monitoring in 2011 found small numbers of birds had recolonised some of the gullies that had experienced rapid post-fire regrowth on Mt Manypeaks, and breeding was confirmed through locating active nests. Further fires in 2015 and early 2016 impacted on occupied habitat between Mt Manypeaks and Two Peoples Bay, and Mt Gardner (the original parent population) where over 90% of known habitat was lost (S. Comer in litt. 2016). Almost all birds are now on protected land, but habitat clearance on private land could cut corridors, fragmenting populations and preventing dispersal. Breeding success is relatively good, but various native and introduced mammals and reptiles may raid nests and kill adults (Danks et al. 1996), and evidence for predation by feral cats was confirmed by the discovery of a scrub-bird feather in the stomach of a feral cat trapped on Mt Gardner (DPaW 2014). Birds in recovering habitat may also be particularly vulnerable to predation by cats Felis catus (Danks 1997, Comer and Danks 2000). The increasing frequency of droughts and heat waves in the region (Dey et al. 2019; Herold et al. 2018) are likely to increase the probability of fire in the region (Di Virgilio et al. 2019, Dowdy et al. 2019).
Conservation Actions Underway
CITES Appendix I. Almost the entire range is within protected areas. The species has undergone 50 years of intense research, monitoring and management, including protection from fire and translocation. The population at Mt Manypeaks was established following translocations in 1983 and 1985 (Comer 2002, Comer and Burbidge 2006). Following a fire at Mt Manypeaks a project was started in March 2005 to begin long-term monitoring of the species's recovery, including studies on invertebrate food resources and the vegetation associated with its habitat, as well as increased fox control, cat trapping and improved fire management capabilities (Danks and Comer 2006). Between June and August 2006, eight males were translocated from the Mermaid-Waychinicup area to karri forest in Porongurup National Park, and fitted with radio transmitters during the process (Anon. 2007). Radio-tracking proved unsuccessful (Berryman 2007), but call monitoring was carried out (Anon. 2007, Berryman 2007), revealing that one male moved 1.2 km from the release site (Berryman 2007). In 2008, following a fire that burnt through the park, only one male from the translocation was still being heard (Tiller 2009) and this bird had disappeared by 2009. Similarly translocations took place in Gull Rock National Park in 2007 but only one bird could be located the following year (Tiller 2009). The search for potential translocation sites continued and in 2010, following significant pre-translocation work, a small group of six scrub-birds (5M:1F) were released as a trial in Jane National Park. Two of the males were predated days after being released. No birds were found in 2011. The recovery of this species is being managed by the South Coast Threatened Birds Recovery Team (A. Burbidge in litt. 2007).
Conservation Actions Proposed
Establish populations where appropriate habitat persists throughout its former range. Understand the effect of changes in vegetation structure and food availability following fire. Maintain active fire protection and habitat management at all sites. Survey and monitor all known populations at five-year intervals. Continue the translocation program. Continue to support coordination of management by the South Coast Threatened Birds Recovery Team.
22-26 cm. Skulking passerine with short, rounded wings, long, rounded tail and characteristically triangular head profile. Adult dark brown above with faint dark barring and contrasting rufous wings. Grey-brown below merging to rufous on vent and undertail-coverts and cream on lower breast. Male has diagnostic blackish triangle on throat with bold whitish stripes at sides. Female has whitish throat. Juvenile unbarred above with rich, buff foreneck and breast. Similar spp. Western Bristlebird Dasyornis longirostris lacks dark barring and has pale scallops on back and breast. Voice Male calls powerful, penetrating and directional. Main territorial song highly variable within and between individuals; generally a sweet, descending crescendo, falling and accelerating into ear-splitting climax.
Text account compilers
Dutson, G., McClellan, R., Benstead, P., Symes, A., Garnett, S., Harding, M., North, A., Taylor, J., Vine, J.
Burbidge, A.H., Garnett, S. & Comer, S.
BirdLife International (2022) Species factsheet: Atrichornis clamosus. Downloaded from http://www.birdlife.org on 07/10/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 07/10/2022.