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Subspecies Conservation Summary Slender-billed Thornbill (Gulf St Vincent) Acanthiza iredalei rosinae Mathews, 1913 Acanthizidae Conservation status Vulnerable B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) Reasons for listing Extent of occurrence is <5000 km2 and birds occupy <500 km2 but not severely fragmented and risk from coastal development, with a consequent decline in EOO, AOO, quality of habitat, and number of locations, subpopulations and mature individuals, is spread across at least 10 locations Status 2000 Vulnerable B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) Status 1990 Vulnerable B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) Taxonomy A. i. hedleyi (south-east South Australia and central western Victoria) and A. i. iredalei (southern arid zone of Western Australia and South Australia west to Spencer Gulf) are Least Concern, as is the species Taxonomic uniqueness: medium (14 genera/family, 12 species/genus, 3 subspecies/species) Range This subspecies is patchily distributed around the northern shores of the Gulf of St Vincent, South Australia (Higgins and Peter 2002) from St Kilda to Ardrossan with 3 population foci: Price, Clinton Conservation Park to Sandy Point and Port Prime south to Torrens I. (Matthew 1994). The Price and Clinton Conservation Park regions are assumed to exchange birds occasionally along the narrow coastal strip as there is a record from between the 2 at Port Arthur (Matthew 1994). Specimens were collected at Port Broughton, Spencer Gulf, in 1917, but there have been no records since (Matthew 1994) despite searching. This subpopulation is assumed to have been lost, and may in case have been more closely related to A. i. iredalei than A. i. rosinae (L. Pedler in litt.). The bird has also probably disappeared from around Port Adelaide (Matthew 1994). It is assumed that some of the loss has occurred within the last 3 generations (37 years), constituting a small but continuing decline. The AOO is calculated from the approximate area of suitable habitat around Gulf St Vincent. Given the number of tenures within the AOO, there are at least 10 locations, though many of the smaller ones would not hold viable populations on their own. Abundance There are probably about 4300 mature individuals. Based on densities of about 5.6 birds/ha, and adjusting the esti- mates of maximum numbers from Matthew (1994) to his subsequent lower estimate of density (Matthew 2002), there are likely to be no more than 600 mature individuals at Price, 2200 from Clinton Conservation Park to Sandy Point, and about 1500 from Port Prime south to Torrens I. (assuming lower densities than at Clinton Conservation Park; Matthew 1994). Matthew (1994) thought there might still be 1000 birds on Spencer Gulf but, after 93 years, this assumption is not made here, especially given the taxonomic uncertainty. The subspecies has also disappeared from around Port Adelaide (Matthew 1994). Ecology Occupies chenopod shrublands, particularly samphire dominated by Sclerostegia arbuscula, on narrow coastal saline mudflats, usually within 20 m of a tidal channel or saline lakes. It also occasionally feeds in Grey Mangrove Avicennia marina and among other chenopod species (Mathew 1994, 2002). They build globular nests in low shrubs, laying 2–4 eggs (Higgins and Peter 2002). Densities of 2.9–8.4 birds/ha have been recorded in suitable habitat at Clinton Conservation Park, but are thought to be lower in the southern subpopulation (Matthew 1994). A generation time of 12.3 years (BirdLife International 2011) is derived from an age at first breeding of 1.0 years (extrapolated from congeners) and a maximum longevity of 23.5 years (extrapolated from Striated Thornbill A. striatus, Australian Bird and Bat Banding Scheme). Threats This subspecies has suffered from habitat loss, particularly cumulative minor developments in the southern part of its range (Grady and Brook 2002), though its disappearance from Port Broughton is unexplained. Though generally unattractive for rural or residential development, the fringes of some salt-flats have been reclaimed for recreational and industrial use, such as for salt works. Other coastal residential and commercial developments, such as marinas, are proposed in parts of the subspecies’ range. Inappropriate water management and use also © Birds Australia 2011 Published by CSIRO Publishing, http://www.publish.csiro.au/ Citation: Garnett ST, Szabo JK, Dutson G (2011) The Action Plan for Australian Birds 2010. CSIRO Publishing, Melbourne. Current eligibility against IUCN Red List Criteria IUCN category A Criteria eligibility Not applicable: past, current or future population declines are thought unlikely to exceed 20% in any 3-generation period B Vulnerable: EOO <20 000 km2, AOO <2000 km2, population at ≤10 locations, inferred continuing decline in EOO, AOO, area, extent and quality of habitat, no. locations, no. subpopulations, no. mature individuals C Not applicable: population 2500–10 000 mature individuals, continuing decline not observed or estimated, largest subpopulation >1000 mature individuals, >1 subpopulation D Not applicable: population >1000 mature individuals, >5 locations E Not applicable: no population viability analysis undertaken IUCN Red List assessment data Estimate Reliability Extent of occurrence trend 1600 km2 decreasing high medium Area of occupancy trend 60 km2 decreasing medium medium No. of mature individuals trend 4300 decreasing low medium No. subpopulations 2 medium No. locations 10 medium 2200 low Largest subpopulation Generation time Global population share 12.3 years low 100% high threaten their habitat. Other threats include recreational activities and site disturbance, grazing and disturbance by rabbits Oryctolagus cuniculus and predation by foxes Vulpes vulpes and feral and uncontrolled cats Felis catus (Willson and Bignall 2009). Grady M, Brook J (2000) ‘Submission by The Conservation Council of South Australia Inc. to the Senate Inquiry into Gulf St Vincent’. The Conservation Council of South Australia Inc., Adelaide. Retrieved 10 May, 2011 from <http:// www.ccsa.asn.au/submissions/gulfstvincent.htm>. Conservation objectives 1. Existing subpopulations retained and viable Higgins PJ, Peter JM (Eds) (2002) Handbook of Australian, New Zealand and Antarctic Birds. Volume 6: Pardalotes to Spangled Drongo. Oxford University Press, Melbourne. Information required 1. Population trends, particularly near developed areas 2. Impacts of proposed threats 3. Extent of movement between subpopulations/regions Management actions required 1. Establish annual monitoring sites, particularly at fringes of range 2. Determine genetic connectivity between subpopulations/regions 3. Work with local government and the Coast Protection Board to secure all remaining habitat Bibliography Matthew J (1994) The status, distribution and habitat of the Slender-billed Thornbill Acanthiza iredalei in South Australia. South Australian Ornithologist 32, 1–23. Matthew JS (2002) Notes on the ecology of the Slender-Billed Thornbill Acanthiza iredalei rosinae. South Australian Ornithologist 34, 15–22. Willson A, Bignall J (2009) ‘Regional recovery plan for threatened species and ecological communities of Adelaide and the Mount Lofty Ranges, South Australia’. Department for Environment and Heritage, South Australia. Comments received from Graham Carpenter, Jamie Matthew, Lynn Pedler BirdLife International (2011) ‘Species factsheet: Acanthiza iredalei’. Retrieved 17 January, 2011 from <http://www.birdlife.org/>. © Birds Australia 2011 Published by CSIRO Publishing, http://www.publish.csiro.au/ Citation: Garnett ST, Szabo JK, Dutson G (2011) The Action Plan for Australian Birds 2010. CSIRO Publishing, Melbourne.