15 AUSTRALIAN Field Ornithology 2012, 29, 15–22 Distribution of the Thick-billed in the Northern Territory

ANDREW B. BLACK South Australian Museum, North Terrace, Adelaide, South 5000 (Email: [email protected])

Summary Contrary to conventional views, Thick-billed Amytornis modestus in the Northern Territory were not distributed continuously. They occurred as two subspecies separated by up to 200 km and in distinct habitats. The nominate A.m. modestus is now presumed long extinct, but formerly occurred in a limited area of central Australia in valley floors of the upper Finke River drainage, whereas a small population presumed to be of the subspecies A.m. indulkanna occurs near the Northern Territory–South Australia border. About 100 km south of that population are further records of the latter subspecies, which occupies a large area of the western Lake Eyre drainage basin in South Australia. Further field searches are needed to establish both the size and degree of isolation of the small remnant Northern Territory population.

Introduction Storr (1977, p. 80) described the former distribution of the Thick-billed Grasswren Amytornis modestus (North, 1902) in the Northern Territory (NT) as ‘from Mereenie Bluff and the upper Hugh, south to Laurie’s Creek, McMinn’s Creek [Illamurta] and the lower Finke’ but considered the species extinct in the NT since 1936. Eldridge & Pascoe (2004) reported recent observations of the species near the Finke River floodout close to the South Australian (SA) border and suggested (p. 183) that it had once been distributed ‘throughout the entire Finke River drainage basin’ (Figure 1). This species was one of three collected from within the MacDonnell and associated Ranges during the 1894 Horn Expedition to central Australia. The others were the Dusky A. purnelli (Mathews, 1914) and Striated A. striatus (Gould, 1840) Grasswrens, but neither the Thick-billed nor was recognised as a ‘new’ species, both being misidentified as A. textilis (Dumont, 1824), the (North 1896). North (1902) subsequently recognised the Thick-billed Grasswren as a distinct species A. modestus but continued to regard the Dusky as A. textilis. The latter was subsequently named as a species, A. purnelli, by Mathews (1914). It was recognised as a species in the Royal Australasian Ornithologists Union’s official checklist of 1926 (RAOU Checklist Committee 1926), but was subsequently reduced to a subspecies of A. textilis in the eighth supplement to the checklist (RAOU Checklist Committee 1960) following Keast (1958). Parker (1972) returned the Dusky Grasswren to a full species but combined the Western and Thick-billed Grasswrens. Schodde (1982a) followed Parker (1972) but, in the same year and in another context, Schodde (1982b: pp. 213–214, 216) presented an alternative view that the Western Grasswren, including the subspecies occurring on the Eyre Peninsula of SA, and Thick-billed Grasswren were separate species. Black et al. (2010) confirmed the latter with morphological, genetic and biogeographical evidence supporting separate species status. They further showed that central Australian Thick-billed Grasswrens are phenotypically and taxonomically distinct from SA populations; the former represent the nominate A.m. modestus and the latter include the north- western SA subspecies A.m. indulkanna (Mathews, 1916). In this paper I explore AUSTRALIAN 16 BLACK Field Ornithology

The clutch of grasswren eggs, allegedly from Erldunda, collected by Cowle and sent to Keartland. Now held in the Royal Scottish Museum. Plate 3 Photo: Bob McGowan the taxonomic distinction between the central Australian and South Australian populations in relation to an historical review of the distribution and habitats of Thick-billed Grasswrens in the NT.

Methods I have reviewed information on the distribution and habitat of Thick-billed Grasswrens in the NT contained in published reports and in museum databases (as cited below). I have examined all skin specimens of the Amytornis textilis–modestus complex (Western and Thick-billed Grasswrens) in the South Australian Museum, Adelaide (SAMA), Australian Museum, Sydney (AM), Museum Victoria, Melbourne (MV), Australian National Wildlife Collection, CSIRO Sustainable Ecosystems, Canberra (ANWC), and Western Australian Museum, Perth. I have also examined all clutches of eggs of the A. textilis–modestus complex (24 clutches of Western Grasswren, and 50 clutches of Thick-billed Grasswren), and all clutches of Striated A. striatus (48 clutches) and Dusky A. purnelli (10 clutches) Grasswrens in the SAMA, AM, MV and ANWC.

Results and discussion

Published distributional records Parker (1972) identified the following localities for A. modestus in the NT (see Figure 1): • Laurie’s Creek, comprising two specimens (originally labelled 40C and 40D), which probably vanished at an early date (see Black 2011), and VOL. 29 (1) MARCH 2012 Thick-billed Grasswren in NT 17

Figure 1. Map of central Australia showing places mentioned in the text, including locations of specimen records of Thick-billed Grasswrens A.m. modestus (solid squares) and other confirmed records, all presumably of subspecies A.m. indulkanna (solid triangles). HS = homestead, R = river.

Idracowra, comprising an unlocated specimen that probably never existed (see Black 2011); these specimens were from the 1894 Horn Expedition (North 1896, 1902; Keartland 1904); • Hermannsburg and the surrounding Mission Plain, specimens (White 1914; Whitlock 1924); • the upper Hugh River, west of , specimen (White 1914); • Mereenie Bluff and Illamurta (now Illamurta Springs Conservation Reserve), the type specimens, collected by Constable C.E. Cowle of Illamurta (North 1902); and • near Old Crown Station, on the lower Finke River, a sight record only (Whitlock 1924). AUSTRALIAN 18 BLACK Field Ornithology

Parker (1972) doubted the tentative claim of Jarman (1953) from Palm Valley, and regarded a clutch of eggs taken at Hermannsburg in August 1936 by H. Collins, and now in the collection of the late Jack Bourne of Bool Lagoon, SA, as the last authentic record to have been made in the NT. Since Parker (1972) there have been further reports of the species in the NT, but all have been from near the SA border, farther south than the earlier records: a sighting east of Kulgera in September 1967 by Len Harvey (Black & Longmore 2009), and observations east of Charlotte Waters near the Finke River floodout in August 1994 by Julian Reid (Eldridge & Reid 2000; Black & Baxter 2003). In the latter area they have been seen at up to four sites by Steve Eldridge and others in 1995, 2003, 2004, 2005, 2006 and, possibly, 2008 (Eldridge & Pascoe 2004; Pavey 2006; C. Pavey pers. comm.; J. Reid pers. comm.). There is a 1992 sight record from ~16 km south-west of that area in SA (R. Brandle pers. comm.), but otherwise the nearest known localities to the Finke River floodout in the NT are >100 km distant on Macumba and Todmorden Stations. At a similar distance, the nearest locality south of Kulgera is the Indulkana Range, where the type specimen of A.m. indulkanna was obtained (Mathews 1916; Black et al. 2011; Figure 1).

Clutches from central Australia At least 21 clutches of grasswren eggs were collected by Cowle, and sent to Keartland, between October 1895 and February 1903 (I. Mason pers. comm.; ABB unpubl. data). Six were said to be eggs of the A. striatus—four clutches from Illamurta and one each from Idracowra and Erldunda. The remaining clutches included eight listed as A. textilis, five as A. modestus and two as A. purnelli, but I could not determine how Keartland made such identifications. Localities named are: Illamurta (seven clutches), ‘central Australia’ (four clutches), and Mereenie Bluff, Stokes Pass, ‘Alice Springs’ and Erldunda (the latter four all single clutches). Beruldsen (2003) described eggs of the Striated Grasswren (p. 284) as ‘white, slightly lustrous and spotted and blotched over the whole shell, but mostly towards and over the larger end, with pale reddish-brown and some underlying markings of lavender’; those of the Thick-billed Grasswren (p. 286) as ‘white to pinkish-white, slightly lustrous and spotted and blotched over the whole shell, but mostly towards and over the larger end, with rich reddish-brown and some underlying markings of lavender’; and eggs of the Dusky Grasswren as ‘difficult to distinguish in colour, size, clutch or shape from those of [the Thick-billed Grasswren]’. Earlier Campbell (1900) and North (1901–04) had recognised that eggs of the Striated Grasswren were rather finely and lightly speckled compared with the more boldly spotted eggs of ‘the Grass-Wren A. textilis’ (actually Thick-billed or Dusky Grasswrens, or both). Based on my examination of eggs of Striated, Dusky, Western and Thick-billed Grasswrens (see Methods), the ground-colour of eggs is: white to creamy white in Striated Grasswren; off-white to pale pink in Dusky Grasswren; off-white to pink in Western Grasswren; and white, off-white or very pale pink in Thick-billed Grasswren. The varyingly dark reddish to reddish-brown spotting of the eggs is: very light or light, occasionally moderately heavy, in the Striated Grasswren; moderately heavy to heavy in the Dusky Grasswren; moderately heavy in the Western Grasswren; and light to heavy in the Thick-billed Grasswren. A coalescent zone of similar colour at the broader end is present: occasionally in eggs of the Striated Grasswren; in only a very few eggs of the Dusky Grasswren; in most eggs VOL. 29 (1) MARCH 2012 Thick-billed Grasswren in NT 19 of the Thick-billed Grasswren; and in almost all eggs of the Western Grasswren (ABB unpubl. data). I found, consistent with Campbell (1900), North (1901–04) Beruldsen (2003) and Johnstone & Storr (2004), that the generally much paler and less-heavily marked eggs of Striated Grasswrens (including three Cowle–Keartland clutches), were readily distinguished from the others [see illustrations in Beruldsen 2003 (p. 132), Johnstone & Storr 2004 (pp. 386–387) and Black & Longmore 2009 (pp.136–137)]. Most Dusky Grasswren eggs appear darker than eggs of Western and Thick-billed Grasswrens, largely because the markings are generally heavier and more evenly distributed. Eggs of Thick-billed Grasswrens tend to be paler than eggs of Western Grasswrens, especially at the narrower end, but the degree of overlap between eggs of these three species did not allow me to assign to species the 12 individual Cowle–Keartland clutches examined that were named variously Thick-billed, Dusky or (erroneously) Western (A. textilis) Grasswrens. On the other hand, none of these 12 clutches contained eggs resembling those of the Striated Grasswren.

Observations of habitat North (1896, p. 81) reported that eggs sent by Cowle to Keartland shortly after the return of the Horn Expedition (named ‘textilis’ at the time) were from nests ‘found at the foot of cane grass [Zygochloa] on banks of creeks’, which indicates (see below) that they were eggs of the Thick-billed Grasswren Amytornis modestus. Despite this, Keartland stated in the same report (p. 81) that they were ‘limited to the rocky gorges and sides of the ranges’, which is habitat of the Dusky Grasswren A. purnelli. North (1901–04) and Keartland (1904) were never certain of the habitat preferences of the two species and generally transposed them. Whitlock (1924, p. 269), however, was precise and referred to central Australian A. modestus as the ‘Cane Grass Wren’; he described the habitat on Mission Plain, Hermannsburg, where he obtained eight or nine of 10 skin specimens, saw many nests and took clutches, as ‘a long narrow flat, abundantly clothed with flourishing clumps of [Sandhill] canegrass [Zygochloa] paradoxa, with a few much eaten saltbushes’. Whitlock thought he might also have seen the species ‘with some difficulty’... ‘some five or six miles east of the Mission in soft spinifex (Triodia pungens) and a little mallee’ but, as noted by Parker (1972), those were most likely to have been Striated Grasswrens which he did not otherwise record. White (1914, p. 432) declared that they were ‘always in the dry sandy watercourses’, and he and Whitlock (1924) observed that they occasionally nested in, or took refuge in, masses of flood debris in the river bed. In agreement with Parker (1972), I doubt Jarman’s (1953) possible records from Palm Valley, which were said to be in stony areas; Whitlock had examined the locality thoroughly and recorded (and collected skins and eggs of) only A. purnelli. The last authenticated record of central Australian A. modestus, the 1936 Hermannsburg clutch, was taken from ‘a nest in a large clump of cane-grass on the river bank’ (Parker 1972, p. 161). Keartland (1904) himself made one clear reference to the canegrass habitat of A. modestus, although (as above) he mixed the species (named ‘textilis’, by which he implied the Dusky Grasswren A. purnelli) as well as the locality (see below). In contrast, the most recent records from the NT near the SA border have not been in canegrass. Eldridge & Pascoe (2004, p. 183) described their occurrence ‘in a drainage line amongst gibber, dominated by old-man saltbush Atriplex nummularia (dwarf variant) [ = subspecies omissa ‘Oodnadatta Saltbush’] and bluebush Maireana sp.’ Pavey (pers. comm.) described the habitat as dominated by Old Man Saltbush Atriplex nummularia with Cottonbush Maireana aphylla and other chenopods. AUSTRALIAN 20 BLACK Field Ornithology

Conclusions and uncertainties The localities named (pp. 16–18) for Thick-billed Grasswrens in the NT (listed from north to south) are: Mereenie Bluff, Stokes Pass, the upper Hugh River, Hermannsburg, Laurie’s Creek, Illamurta, Idracowra, Erldunda, Old Crown Station, and near Charlotte Waters. The Idracowra record inferred by Parker (1972) is erroneous and is based on Keartland (1904), who described his frustration at nearly destroying two specimens of a that he had not seen before after a prolonged chase through canegrass. The extreme damage of these specimens, undoubtedly the two from Laurie’s Creek, explains why they ‘vanished at an early date’ (Parker 1972, p. 158); that is, they were probably discarded from the AM very soon after being received there (see Black 2011). Between Illamurta and Old Crown Station is a gap of ~200 km, with the Erldunda clutch the only intervening record. All records from Illamurta and northward appear to have been in habitat of very restricted occurrence: Sandhill Canegrass on or near sandy beds and banks of the upper Finke River drainage, and with a total range of perhaps only ~100 × 200 km. Recent records from near Charlotte Waters (south-east of Old Crown Station) have been from habitat more typical for the species: chenopod on stony flats and drainage lines, the dominant species being Oodnadatta Saltbush and Cottonbush. Low of Oodnadatta Saltbush and Cottonbush accounted for 73% of all habitats at sites where grasswrens were recorded throughout the distribution of the north-western SA subspecies A.m. indulkanna (Black et al. 2011). The area surrounding Erldunda contains no Sandhill Canegrass in sandy creek beds that might support central Australian Thick-billed Grasswrens and, although there is much porcupine grass Triodia spp. on sand-dunes suitable for the Striated Grasswren, there is none on rocky hills or gorges suitable for the Dusky Grasswren (C. Nano pers. comm.). To the south-east of Erldunda, however, there are stony areas with scattered Oodnadatta Saltbush and Cottonbush (C. Nano pers. comm.; J. Reid pers. comm.), the habitat of more recent southern NT and northern SA records of Thick-billed Grasswrens. The Erldunda clutch is in the Royal Scottish Museum, labelled ‘Amytis textilis Grass Wren, Erldunda C.A.’. A photograph (Plate 3) forwarded by Bob McGowan, Curator of Birds, Royal Scottish Museum, shows eggs that are not those of Striated Grasswren but could be of either Thick-billed or Dusky Grasswren. It is possible, therefore, that this clutch represents the most northerly of all southern NT records but it is also plausible that the locality is erroneous, as were many of Keartland’s localities. Erldunda is slightly less than 100 km from the former Old Crown Station and ~65 km from Kulgera. I conclude that the distribution of the Thick-billed Grasswren in the NT consists of two disjunct populations separated by 100–200 km and occupying distinct environments: one in the sandy river-valley floors within the ranges and another on open stony plains and continuous (albeit tenuously) with the north- western SA population. The former population, now presumed extinct, was of the long-tailed, darker subspecies A.m. modestus. The other persists in low open chenopod shrublands that are more typical for the species, and is almost certainly of the wide-ranging short-tailed subspecies A.m. indulkanna of north-western SA (Black et al. 2010; Black 2011). Because of pervasive ambiguities surrounding the identity and habitats of two of the three apparently sympatric grasswren species encountered by the Horn VOL. 29 (1) MARCH 2012 Thick-billed Grasswren in NT 21

Expedition of 1894, the distributional limits and other knowledge of the presumed extinct central Australian subspecies of Thick-billed Grasswren must rely largely on documentation retained with, or otherwise related to, skin specimens, all old and some apparently discarded. Another source of information, the large number of variously or incorrectly named clutches collected by Cowle, and sent to Keartland, has proved of limited value because their identity has not been determined with confidence. It is possible that, if examined concurrently with a large and reliably named series, or if diagnostic DNA could be extracted from them, some or all might prove identifiable, but this would not overcome the uncertainties of their places of origin. Further fieldwork is needed to investigate the possible presence of Thick-billed Grasswrens between Charlotte Waters, Kulgera and Erldunda in the chenopod shrublands of the subspecies A.m. indulkanna; it is also important to establish whether grasswrens are distributed continuously between the NT–SA border region and known localities farther south. Although nominate A.m. modestus is almost certainly extinct, it is possible that it yet survives within the ranges in its preferred habitat of Sandhill Canegrass in sandy river beds of the upper Finke River drainage. Attention is also drawn to the former presence of Striated Grasswrens at several places in the area covered by this review: Illamurta, Idracowra, Alice Well (North 1896), Erldunda and east of Hermannsburg (Whitlock 1924). There have been few if any recent records of Striated Grasswrens east of Uluru (J. Reid pers. comm.), and further search effort should be directed towards that species too.

Acknowledgements I thank Bob McGowan for details and the photograph of the ‘Erldunda’ clutch and Brian Blaylock and Graham Carpenter for preparation of the map; Chris Pavey, Julian Reid and Catherine Nano for information concerning the vegetation of the area surrounding Erldunda; also Ian Mason, CSIRO, Canberra, for his help with egg collections; and Philippa Horton, South Australian Museum, and Wayne Longmore, Museum Victoria, who have supported my grasswren interests over several years. I am grateful also to reviewers Chris Pavey and Julian Reid and editor Peter Higgins for very constructive advice for improvements to the submitted draft.

References Beruldsen, G. (2003), Australian Birds Their Nests and Eggs, Author, Kenmore, Qld. Black, A.B. (2011), ‘What became of the first Thick-billed Grasswren specimens from central Australia?’, Australian Field Ornithology 28, 84–87. Black, A.B. & Baxter, C.I. (2003), ‘Observations of Thick-billed Grasswrens on the North Olary Plains’, South Australian Ornithologist 34, 70–74. Black, A.B. & Longmore, N.W. (2009), ‘Notes on grasswren eggs in Len Harvey’s collection, Museum Victoria’, Australian Field Ornithology 26, 132–141. Black, A., Carpenter, G. & Pedler, L. (2011), ‘Distribution and habitats of the Thick-billed Grasswren Amytornis modestus and comparison with the Western Grasswren Amytornis textilis myall in South Australia’, South Australian Ornithologist 37, 60–80. Black, A.B., Joseph, L., Pedler, L.P. & Carpenter, G.A. (2010), ‘A taxonomic framework for interpreting evolution within the Amytornis textilis–modestus complex of grasswrens’, Emu 110, 358–363. Campbell, A.J. (1900), Nests and Eggs of Australian Birds, Author, Sheffield, UK. Eldridge, S. & Pascoe, B. (2004), ‘Northern Territory records of the Thick-billed Grasswren Amytornis textilis and Rufous Fieldwren Calamanthus campestris’, South Australian Ornithologist 34, 183–184. Eldridge, S. & Reid, J. (2000), A Biological Survey of the Finke Floodout Region, Northern Territory, Arid Lands Environment Centre, Alice Springs, NT. AUSTRALIAN 22 BLACK Field Ornithology

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Received 27 October 2010 