Red-tailed black-cockatoo (inland subspecies) (Calyptorhynchus banksii samueli) - vulnerable species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Red-tailed Black-Cockatoo (inland subspecies) Calyptorhynchus banksii samueli Mathews, 1917 as a VULNERABLE SPECIES in Part 1 of Schedule 2 of the Act, and as a consequence, to omit reference to Calyptorhynchus banksii (Latham, 1790) from Part 1 of Schedule 2 (Vulnerable species) of the Act. Listing of Vulnerable species is provided for by Part 2 of the Act.
NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Red-tailed Black-Cockatoo is a large (60 cm) black cockatoo with a bushy crest and a red tail panel; the female has a white bill, fine yellow spots and bars on the head and body, and an orange tail panel with fine black bars. It is very similar to the smaller Glossy Black-Cockatoo, which has a small crest, softer and less discordant calls, and females have a grey bill and large yellow blotches on the head. The Yellow-tailed Black-Cockatoo has a yellow ear patch and tail panel, and loud wailing calls.
2. The Red-tailed Black-Cockatoo is distributed throughout much of Australia, but its southern and inland populations are fragmented into isolates that constitute separate subspecies (Higgins, 1999). In NSW, the Red-tailed Black-Cockatoo (inland subspecies) C. b. samueli, is typically found in the Darling Riverine Plain Bioregion. It is known to occur on the Darling River south to about Menindee, and its northern tributaries upstream to about Nyngan on the Bogan River, and Walgett or possibly Boggabilla on the Barwon River (Higgins 1999). It inhabits riparian woodland and adjacent wooded plains, and nests in large hollow trees. Given the high mobility of this species (Higgins 1999) the inland NSW birds are likely to constitute a single subpopulation, which may have interchange with the Queensland population or retreat into Queensland during drought in NSW. Recent reports of ‘Red-tailed’ Black-Cockatoos on the slopes and tablelands of NSW are referable to the Glossy Black-Cockatoo.
3. The precise number of C. b. samueli in inland NSW is unknown, but where flocks of hundreds were regularly reported at some sites ( e.g. Bourke) before 2000, observed flocks now number in the tens or rarely up to 100 (NSW Field Ornithologists Club annual bird reports). In November 2002, during a drought period when C. b. samueli would be expected to forage and roost near rivers, a survey was conducted along the Barwon-Darling Rivers between Walgett and Menindee (M. Cameron in litt. November 2008). Surveyors estimated a population of 1600 birds were present in this core range of the species. No new areas of concentrated numbers have been reported in recent years. On this basis, the number of mature individuals in NSW is very likely to be moderately low.
4. The subspecies was reported in 18 one-degree grids in NSW in the first national bird atlas in 1977-81, at low to high reporting rates (Blakers et al. 1984), and 12 one-degree grids in the second national bird atlas in 1998-2002, at low to moderate reporting rates (Barrett et al. 2003). Its index of abundance (reporting rate) declined by 34% between the two atlases over 20 years ( i.e. only one generation). This is a non-significant trend (Barrett et al. 2007), probably owing to the small sample size of records, yet suggests a possible decline of much more than 30% may have occurred or be occurring over three generations (60 years). The Darling Riverine Plains Bioregion has had 23% of its native vegetation cleared to date (all types, including non-woody vegetation), 97% of its area is grazed, and it has a moderate landscape stress rating of 3 out of 6 (Barrett et al. 2007). These values are probably conservative estimates of recent impacts on C. b. samueli as approximately 1800 km2 of coolibah-dominated woodland alone has been cleared on the upper Darling floodplain in NSW during the past two decades (NSW Scientific Committee unpublished data). Cox et al. (2001) also documented substantial clearing of other woodland types, including more upland types such as those containing poplar box, in the same region between 1985 and 2000. Clearing has targeted riparian and floodplain woodland in the north-east of the bioregion during the past 30 years with the expansion of cotton farming and other cropping. It thus affected the cockatoo’s breeding sites, although a concurrent decrease in its food supply is uncertain given that the cockatoo can eat the seeds of some weed species.
5. The main threat to the species comes from clearing of riparian eucalypts, especially individual old trees with large hollows, and there is a lack of recruitment into this age class under current land management regimes. Another subspecies, C. b. graptogyne (listed federally, and in Victoria and South Australia, as Endangered) is adversely affected even by loss of dead nesting trees in paddocks (Maron 2005), a situation that is inferred to apply in the upper tributaries of the Darling Riverine Plains Bioregion. Other threats include overgrazing, which degrades habitat and causes loss of riparian trees through erosion of river banks; cultivation of riparian flats, which may negatively affect food supply and deny water to riparian trees (thus causing tree death); and poaching for aviculture (including destruction of nests to obtain chicks). Birds in noisy communal roosts are also sometimes illegally shot. An unexplained dieoff of C. b. samueli was documented in 2002 along the Barwon River (M. Cameron in litt. November 2008). Necropsies indicated that the birds had died from neither starvation nor pesticide poisoning. An unidentified disease or toxin may have caused this dieoff. ‘Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands’, ‘Clearing of native vegetation’, ‘Loss of Hollow-bearing Trees’ and ‘Removal of dead wood and dead trees’ are listed as Key Threatening Processes under the NSW Threatened Species Conservation Act 1995.
6. Calyptorhynchus banksii samueli is not listed as threatened under other state or federal legislation. The separate population in the Tweed River area of far north-east NSW is the nominate subspecies C. b. banksii, which is unlikely to have interchange with the inland population. In Queensland C. b. samueli is sparsely distributed on major watercourses in the Channel Country and Mitchell Grass Downs Bioregions, except for concentrations on the upper Cooper Creek. The core Queensland population is distant (400 km) from the NSW population (Higgins 1999; Barrett et al. 2003).
7. Calyptorhynchus banksii samueli Mathews, 1917 is not eligible to be listed as an Endangered or Critically Endangered species.
8. The Red-tailed Black-Cockatoo (inland subspecies) Calyptorhynchus banksii samueli Mathews, 1917 is eligible to be listed as a Vulnerable species as, in the opinion of the Scientific Committee, it is facing a high risk of extinction in New South Wales in the medium-term future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:
Clause 14
The species has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time frame appropriate to the life cycle and habitat characteristics of the taxon:
(c) a moderate reduction in population size,
based on:
(d) an index of abundance appropriate to the taxon
(e) geographic distribution, habitat quality or diversity, or genetic diversity.
Clause 16
The estimated total number of mature individuals of the species is:
(c) moderately low,
and:
(d) a projected or continuing decline is observed, estimated or inferred in:
(i) an index of abundance appropriate to the taxon
(ii) geographic distribution, habitat quality or diversity, or genetic diversity.
Dr Richard Major
Chairperson
Scientific Committee
Proposed Gazettal date: 31/07/09
Exhibition period: 31/07/09 - 25/09/09
References:
Barrett G, Silcocks A, Barry S, Cunningham R, Poulter R (2003) ‘The new atlas of Australian birds.’ (RAOU: Melbourne)
Barrett GW, Silcocks AF, Cunningham R, Oliver DL, Weston MA, Baker J (2007) Comparison of atlas data to determine the conservation status of bird species in New South Wales, with an emphasis on woodland-dependent species. Australian Zoologist 34, 37-77.
Blakers M, Davies SJJF, Reilly PN (1984) ‘The atlas of Australian birds.’ Melbourne University Press: Melbourne)
Cox J, Sivertsen DP, Bedward M (2001) Clearing of native woody vegetation in the NSW Wheatbelt: extent, rate of loss and implications for biodiversity conservation. Cunninghamia 7, 101-155.
Higgins PJ (Ed.) (1999) ‘Handbook of Australian, New Zealand and Antarctic birds (Vol. 4).’ (Oxford University Press: Melbourne)
Maron M (2005) Agricultural change and paddock tree loss: implications for an endangered subspecies of Red-tailed Black-Cockatoo. Ecological Management and Restoration 6, 207-212.
NSW Field Ornithologists Club (1990-2007) NSW annual bird reports, published annually in Australian Birds.