White-throated Grasswren Amytornis woodwardi · In a survey in Warddeken in 2012, grasswrens were found nearly everywhere that they were expected based on fire history and habitat

Threatened Species Strategy – Year 3 Priority Species Scorecard (2018)

1 Information current to December 2018

White-throated Grasswren Amytornis woodwardi

Key Findings

White-throated Grasswrens historically occurred across the Arnhem Land sandstone. However, due to its reliance on large unburnt spinifex patches and the fire history of the habitat, numbers are likely to have declined as the habitat has become fragmented. Intensive fire management in Arnhem Land over the last decade has reduced the total area affected by destructive late season fires, allowing more spinifex to mature to an age when it can support White‑ throated Grasswren. Photo: Peter Cooke

Significant trajectory change from 2005-15 to 2015-18? Yes, was declining and now increasing.

Priority future actions

• Continue effective fire management across the range of the species, allowing recovery of old growth spinifex across the landscape.

• Localised cat and rat control if a proven problem for the grasswrens

Full assessment information Background information

1. Conservation status and taxonomy 2. Conservation history and prospects 3. Past and current trends 4. Key threats 5. Past and current management 6. Support from the Australian Government 7. Measuring progress towards conservation

2018 population trajectory assessment

8. Expert elicitation for population trends 9. Immediate priorities from 2019 10. Contributors 11. Legislative documents 12. References 13. Citation

The primary purpose of this scorecard is to assess progress against achieving the year three targets outlined in the Australian Government’s Threatened Species Strategy, including estimating the change in population trajectory of 20 bird species. It has been prepared by experts from the National Environmental Science Program’s Threatened Species Recovery Hub, with input from a number of taxon experts, a range of stakeholders and staff from the Office of the Threatened Species Commissioner, for the information of the Australian Government and is non-statutory. It has been informed by statutory planning documents that guide recovery of the species, such as Recovery Plans and/or Conservation Advices (see Section 11). The descriptive information in this scorecard is drawn from Department of the Environment (2014), unless otherwise noted by additional citations.

The background information aims to provide context for estimation of progress in research and management (Section 7) and estimation of population size and trajectories (Section 8).



1. Conservation status and taxonomy

Taxonomy: No infraspecific taxa described. Taxonomic distinctiveness medium: 5 genera/family, 11 species/genus, 0 subspecies/species.

2. Conservation history and prospects The White-throated Grasswren historically occurred across the Arnhem Land sandstone, including many parts of Kakadu National Park. Early estimates suggested that there could be as many as 50,000 birds, but given the reliance of the species on large unburnt spinifex (Triodia spp.) patches and the fire history of the habitat, numbers have almost certainly declined and been severely fragmented into small sub-populations. Recent success in reducing the frequency and extent of late dry season fires, however, may have allowed some recovery of the population but monitoring is inadequate to determine trends in numbers or distribution of the birds themselves.

3. Past and current trends Based on population density estimates at eight sites, Noske (1992) estimated the total population at c. 50,000 (14,000-182,000) individuals, but Woinarski (1992) suggested a total population of c. 5,000-10,000 individuals. Given the fire history of the habitat, population was estimated as no more than 10,000 mature individuals in Garnett et al. (2010). Woinarski et al. (2012) reported a significant decline in Kakadu National Park, from a mean of 0.08 individuals/quadrat in 2001-2004 (recorded in 6/142 quadrats) to zero in 2010. In a survey in Warddeken in 2012, grasswrens were found nearly everywhere that they were expected based on fire history and habitat (A. Stevens pers.comm.) with 25 birds in 6 groups (55 hours, 95 kms walked, Stevens and Rangers of the Warddeken and Djelk Indigenous Protected Areas 2102). Several local people from Kabulwarnamyo knew the bird. A search in Djelk Indigenous Protected Area was unable to locate birds in the vicinity of a 1996 record, and only one old lady at Kolorbidadah outstation recognised the bird but had not seen it for at least 20 years, while no one spending time in the rock country camping, hunting and fishing recognised the bird at all. Most potential habitat in Djelk is regularly burnt in the early season and there is little spinifex. A survey in Kakadu NP in 2011 found 30 birds at 11 sites in four of 16 locations searched (93 hours, 139 kms, Mahney et al. 2011). A systematic survey in Kakadu NP in 2016 found birds at 4 of 14 sites surveyed (L. Einoder pers. comm.).

Conservation status 2018

IUCN Vulnerable

EPBC Vulnerable

NT Vulnerable



Monitoring (existing programs): In Kakadu NP meander searches with intermittent use of call playback were undertaken in 2011, 2012 and 2014. In 2016 a new monitoring protocol involving timed area searches was instituted and undertaken by the Flora and Fauna Division of NT DENR. In Warddeken Indigenous Protected Area there is regular camera trapping for mammals that also detects grasswrens, but no grasswren specific monitoring program.

Population trends: Tables 1 and 2 summarise the overall trend and status of the White-throated Grasswren. The information provided in these tables is derived from the Conservation Advice (2014), with some adjustments made by contributing experts based on new information.

Table 1. Summary of the available information on White-throated Grasswren distribution and population size, and (where possible) trend estimates between 2015 and 2018 for each parameter.

Population parameters Published baseline 2015 Estimate 2018 Estimate Confidence in

estimates

WILD*

Extent of Occurrence 10,000km2 16,000km2 16,000km2 Low

Area of Occupancy 1000km2 500km2 520km2 Low

Dates of records and methods used

As per Bird Action Plan

No. mature individuals 10,000 1000 1100 Low

Any other measure of relative abundance

Area not burnt in late fires

No. of subpopulations >10 >10 >10 Medium

No. of locations >10 >10 >10 Medium

Generation time 3.2 n/a n/a

High, based on global modelling by

BirdLife International



Table 2. Estimated recent (2005-2015) and current (2015-2018) population trends for the White-throated Grasswren

Sub-population

Est. % of total pop’n (pre-2015)

2005-2015 trend

Confidence in

2005-2015 trend

2015-2018 trend

Confidence in

2015-2018 trend

Est. % of total pop’n (2018)

Details

Warddeken Indigenous Protected Area

90

Low

Low 90

Intensive fire management has greatly decreased the frequency of large scale late dry season burns but no information is available on bird trends

Kakadu NP 5

Low

Low 5

Greater effort is being made to reduce the frequency of late dry season fires, with benefits from neighbouring Warddekken

Djelk Indigenous Protected Area and other Arnhemland populations

5

Low

Low 5

Populations are assumed to exist but there is little knowledge of their extent or the trends in habitat

Whole population

100

Low

Low 100

Trends reflect those of Warddeken where the largest population is thought to persist

KEY:

Improving Stable Deteriorating Unknown Confidence Description

? High Trend documented Medium Trend considered likely based on documentation Low Trend suspected but evidence indirect or equivocal

4. Key threats The threats listed here are derived from the Department of the Environment (2014), with some amendments from contributing experts based on new information. Note that we do not consider all plausible threats, but a subset of the threats that are likely to have the largest impact on populations, though, in this case, there have been no detailed studies of the impacts of putative threats on this species, so the assessment of threats is largely inferential.



Increasing fire frequency and/or extent An increase in extent and frequency of fire is likely to be a threat to the White-throated Grasswren. Fire regimes across western Arnhem Land have been characterised in recent decades by high annual frequencies of large late dry season fires that cover large areas. Despite the rocky habitat offering protection from fires, many are too hot and extensive to leave functional unburned refugia (Garnett et al. 2011).

Weeds The progressive vegetational change, notably annual sorghum Sarga spp., may reduce habitat suitability as well as supporting further hot fires (Russell-Smith et al. 2002) but is unlikely to effect change at a landscape level relevant to the Grasswrens (J. Russell-Smith pers.comm.).

Climate change White-throated Grasswrens have been identified as one of 39 Australian bird species occurring in terrestrial habitats and inland waters that are most exposed to either a loss of climate space or a reduction in climatic suitability. They are also one of 55 Australian bird taxa considered likely to be exposed to increases in the frequency and intensity of fires as a result of climate change (Garnett et al. 2013).

Feral cats (Felis catus) Feral cats are considered a threat to several Grasswren species, particularly following fire (Garnett et al. 2011) but the threat has not been assessed for this species.

Black rats (Rattus rattus) Black rats have recently been recorded within the range of the species but the extent to which they pose a threat is unknown.

The impacts of the major threats are summarised in Table 3.

Table 3. The major threats facing the White-throated Grasswren and their associated impact scores.

CURRENT THREAT IMPACT

Threat Timing Extent Severity

1. Increase in fire frequency/intensity Continuing/ongoing >90% of range 20-29%

2. Feral cats Continuing/ongoing >90% of range 20-29%

3. Black rats Continuing/ongoing 1-50% of range Negligible declines (<1%)

Timing: continuing/ongoing; near future: any occurrence probable within one generation (includes former threat no longer causing impact but could readily recur); distant future: any occurrence likely to be further than one generation into the future (includes former threat no longer causing impact and unlikely to recur). Extent: <1% of range; 1-50%; 50-90%; >90%. Severity: (over three generations or 10 years, whichever is sooner) Causing no decline; Negligible declines (<1%); Not negligible but <20%; 20-29%; 30-49%; 50



5. Past and current management Recent and current management actions thought to be contributing to the conservation of the White-throated Grasswren are summarised in Table 4. This information is a collation of material provided by experts.

Recovery action for the species is guided by Conservation Advice (2014) (see Section 11).

Table 4. Management actions thought to be contributing to the conservation of the White-throated Grasswren.

Action Location Timing Est. %

population Contributors and partners

Landscape scale improved fire management (increased broad-scale patchiness and less severe fire) in part of range (west Arnhem Land): Successfully reducing late dry season fire and increasing broad-scale patchiness with expected benefits to grasswren.

Warddeken Indigenous Protected

Area

2010- 90 Warddeken Indigenous Protected Area

Fire management. Strategic fire management since 2016 has reduced the total area affected by fire from close to 50% in 2014 and 2015 each year to 20%-30% of stone country in 2017 and 2016 and minimised the occurrence of destructive late fires from approximately 30% of stone country with late dry season fire before 2016 to <4% since 2016.

Kakadu National

Park

2016-2018

5 Kakadu National Park, Parks Australia: Kakadu National Park Operational budget

6. Actions undertaken or supported by the Australian Government resulting from inclusion in the Threatened Species Strategy The TSS raised the profile of the species and there has been an increasing effort to find and monitor the birds, particularly in Kakadu National Park where improved fire management is assumed to be allowing grasswren numbers to increase. The “Targeting Threats from Fire, Weeds and Feral Animals in Kakadu National Park” project enabled additional fire management for a short time in several areas of the park.



7. Measuring progress towards conservation Table 5. Progress towards management understanding and management implementation for each of the major threats affecting the White-throated Grasswren in 2015 (i.e. timing of TSS implementation) and 2018, using the progress framework developed by Garnett et al. 2018.

PROGRESS IN MANAGING THREATS

Threat Year Understanding of how to manage threat Extent to which threat being managed

1. Increase in fire frequency/ intensity

2015 2. Research has provided strong direction on how to manage threat

3. Solutions have been adopted but too early to demonstrate success

2018 4. Trial management under way but not yet clear evidence that it can deliver objectives

4. Solutions are enabling achievement but only with continued conservation intervention

2. Feral cats

2015 1. Research being undertaken or completed but limited understanding on how to manage threat

0. No management


0. No management

3. Black rats


0. No management


0. No management

> Green shading indicates an improvement in our understanding or management of threats between years 2015 and 2018, while red shading indicates deterioration in our understanding or management of threats. KEY:

Score Understanding of how to manage threat Extent to which threat is being managed 0 No knowledge and no research No management

1 Research being undertaken or completed but limited understanding on how to manage threat Management limited to trials

2 Research has provided strong direction on how to manage threat

Work has been initiated to roll out solutions where threat applies across the taxon’s range

3 Solutions being trialled but work only initiated recently

Solutions have been adopted but too early to demonstrate success

4 Trial management under way but not yet clear evidence that it can deliver objectives

Solutions are enabling achievement but only with continued conservation intervention

5 Trial management is providing clear evidence that it can deliver objectives

Good evidence available that solutions are enabling achievement with little or no conservation intervention

6 Research complete and being applied OR ongoing research associated with adaptive management of threat

The threat no longer needs management



8. Expert elicitation for population trends An expert elicitation process was undertaken to assess population trends for the period 2005-2015 and post-2015 under the following management scenarios. Please note that differences between Management Scenarios 2 and 3 (Fig. 1) are difficult to attribute, as it can be difficult to determine whether actions undertaken after 2015 were influenced by the Threatened Species Strategy or were independent of it (see Summary Report for details of methods).

Management Scenario 1 (red line): no conservation management undertaken since 2015, and no new actions implemented.

• Fires allowed to burn unimpeded across the landscape • No attempt at cat control

Under this scenario at least 40% of the landscape is likely to burn annually, as happened before any fire management was introduced.

Management Scenario 2 (blue line): continuation of existing conservation management (i.e. actions undertaken before implementation of the Threatened Species Strategy).

• Fire management in Indigenous Protected Areas and Kakadu National Park but with little effort beyond them.

Under this scenario much less of the landscape is burnt, with most fire being during the early dry season when relatively cool.

Management Scenario 3 (green line): continuation of existing management, augmented by support mobilised by the Australian Government under the Threatened Species Strategy.

• As for the Scenario 2 but with slightly more fire management in Kakadu National Park for a short period

Under this scenario the amount burnt in Kakadu National Park was slightly less in 2015-2018.

Overall estimated population trajectories subject to management scenarios considered The White-throated Grasswren is currently being managed under Scenario 3 (green line).



Figure 1. Estimated relative percentage change in population under each of the management scenarios described above. Data derived from 7 expert assessments of White-throated Grasswren expected response to management, using four-step elicitation and the IDEA protocol (Hemming et al. 2017), where experts are asked to provide best estimates, lowest and highest plausible estimates, and an associated level of confidence. The dashed line represents the baseline value (i.e. as at 2015, standardised to 100). Values above this line indicate a relative increase in population size, while values below this line indicate a relative decrease in population size. Shading indicates confidence bounds (i.e. the lowest and highest plausible estimates). NB: upper and lower bounds wider than what is shown in both graphs.

Population size projections based on expert elicitation are extended here to 2025, 2035 and 2045 (i.e. 10, 20 and 30 years after the establishment of the Threatened Species Strategy) on the grounds that some priority conservation management actions may take many years to achieve substantial conservation outcomes. However, we note also that there will be greater uncertainty around estimates of population size into the more distant future because, for example, novel threats may affect the species, managers may develop new and more efficient conservation options, and the impacts of climate change may be challenging to predict.



Improved trajectory (Threatened Species Strategy Year 3 target): The primary purpose of this scorecard is to assess progress against achieving the year three targets outlined in the Australian Government’s Threatened Species Strategy, i.e. a demonstrated improved trajectory for at least half of the priority species (10 birds and 10 mammals). To assess this, we first use the expert-derived trend between 2005-15 (i.e. 10 years prior to implementation of the TSS) as a baseline for assessing whether there has been an improvement in trajectory in the time since implementation of the TSS (i.e. 2015-18). Table 6 below summarises this information, where negative values indicate a declining population, and positive values indicate an increasing population. We used Wilcoxon match-paired tests to compare trajectories for these two periods; a significant result (probability <0.05) indicates that there was a high concordance amongst experts that their trajectory estimates for 2005-15 were different to their estimates for 2015-18.

Table 6. A comparison of the relative annual percentage population change for the periods 2005-2015 and 2015-2018.

Pre-TSS trend (2005-2015)

Post-TSS trend

(2015-2018)

Year 3 target met?

Significant concordance among elicitors?

Annual percentage population change

-4.82 2.47

The trajectory has improved since 2015, with significant concordance among

elicitors.

Additional actions that could improve trajectory The potential impact of carrying out specific additional conservation measures on the population trajectory of the White-throated Grasswren was also evaluated through expert elicitation. Current management includes fire management in kakadu and neighbouring IPAs.

Additional actions that could further improve the population trajectory include:

• Effective fire management across the range of the species persists, allowing recovery of old growth spinifex across the landscape.

• Localised cat and rat control if a proven problem for the grasswrens

Sustained fire management will allow gradual expansion of the area of old spinfex, reconnecting previously isolated groups.



9. Immediate priorities from 2019 The priorities listed here are derived from Department of the Environment (2014), with some amendments made by contributing experts based on new information. Identification of these priorities in this document is for information and is non-statutory. For statutory conservation planning documents, such as Recovery Plans or Conservation Advices, please see Section 11.

Data collection: • Research on threats and pressures that affect the species’ range and abundance, particularly

response to fire management and interaction with feral cats • Continue/expand monitoring of distribution and abundance, ideally coordinated across Warddeken

and Kakadu National Park

Management actions: • Continue fire management in Kakadu National Park and Warddeken to achieve favourable fire

regimes • If necessary, control of feral carnivores at sites where grasswrens known to occur

10. Contributors Luke Einoder, Simon Ward; Nicholas MacGregor (Parks Australia); Michelle Hall; Stephen Garnett, Sarah Legge, John Woinarski, Hayley Geyle (NESP TSR Hub); Guy Dutson; Peter Menkhorst; Richard Loyn.

11. Legislative documents SPRAT profile: http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=564

Department of the Environment (2014). Conservation Advice Amytornis woodwardi whitethroated grasswren. Canberra: Department of the Environment. Available from: http://www.environment.gov.au/biodiversity/threatened/species/pubs/564-conservation-advice.pdf. In effect under the EPBC Act from 06-Nov-2014

12. References Department of the Environment (2014). Conservation Advice Amytornis woodwardi White-throated Grasswren. Canberra: Department of the Environment Garnett, S.T., Franklin, D.C., Ehmke, G., VanDerWal, J.J., Hodgson, L., Pavey, C., Reside, A.E., Welbergen,

J.A., Butchart, S.H.M., Perkins, G.C. and Williams, S.E. (2013). Climate change adaptation strategies for Australian birds. National Climate Change Adaptation Research Facility, Gold Coast.

Garnett, S.T., Szabo, J. and Dutson, G (2010) ‘The Action Plan for Australian Birds 2010’. CSIRO Publishing: Melbourne.

Garnett, S.T., Butchart, S.H.M., Baker, G.B., Bayraktarov, E., Buchanan, K.L., Burbidge, A.A., Chauvenet, A.L.M., Christidis, L., Ehmke, G., Grace, M., Hoccom, D.G., Legge, S.M., Leiper, I., Lindenmayer, D.B., Loyn, R.H., Maron, M., McDonald, P., Menkhorst, P., Possingham, H.P., Radford, J., Reside, A.E., Watson, D.M., Watson, J.E.M., Wintle, B., Woinarski, J.C.Z., and Geyle, H.M. (2018) Metrics

http://www.environment.gov.au/biodiversity/threatened/species/pubs/564-conservation-advice.pdf

http://www.environment.gov.au/biodiversity/threatened/species/pubs/564-conservation-advice.pdf



of progress in the understanding and management of threats to Australian Birds. Conservation Biology https://doi.org/10.1111/cobi.13220.

Hemming, V., Burgman, M.A., Hanea, A.M., McBride, M.F., and Wintle B.C. (2017) A practical guide to structured expert elicitation using the IDEA protocol. Methods in Ecology and Evolution, 9, 169-180.

Noske, R.A., (1992). The status and ecology of the White-throated Grasswren Amytornis woodwardi. Emu, 92(1), pp.39-51.

Russell-Smith, J., Ryan, P. G., & Cheal, D. C. (2002). Fire regimes and the conservation of sandstone heath in monsoonal northern Australia: frequency, interval, patchiness. Biological Conservation, 104(1), 91-106.

Stevens, A. and Rangers of the Warddeken and Djelk Indigenous Protected Areas. (undated). Yirlinkirrkkirr Yirrindjirrin Djirnidjirnirrinjken White-throated Grasswren Amytornis woodwardi. Unpublished report.

Mahney, T., Brennnan, K., Fegan, M., Trikojus, N., Young, S. and Fisher, A. (2011). Yirlin-kirrk-kirr (White-throated Grasswren) Kakadu National Park Survey 2011. Biodiversity Conservation Division, Department of Natural Resources, Environment, The Arts and Sport.

Woinarski JCZ (1992) The conservation status of the white-throated grass-wren Amytornis woodwardi, an example of problems in status designation. Northern Territory Naturalist 13, 1-5.

Woinarski, J.C.Z., Fisher, A., Armstrong, M., Brennan, K., Griffiths, A.D., Hill, B., Choy, J.L., Milne, D., Stewart, A., Young, S. and Ward, S. (2012). Monitoring indicates greater resilience for birds than for mammals in Kakadu National Park, northern Australia. Wildlife Research, 39 (5), pp.397-407.

13. Citation Please cite this document as: National Environmental Science Program Threatened Species Research Hub (2019) Threatened Species

Strategy Year 3 Scorecard – White-throated Grasswren. Australian Government, Canberra. Available from: http://www.environment.gov.au/biodiversity/threatened/species/20-birds-by-2020/white-throated-grasswren

http://www.environment.gov.au/biodiversity/threatened/species/20-birds-by-2020/white-throated-grasswren

http://www.environment.gov.au/biodiversity/threatened/species/20-birds-by-2020/white-throated-grasswren

Documents

White-throated Grasswren Amytornis woodwardi · In a survey in Warddeken in 2012, grasswrens were found nearly everywhere that they were expected based on fire history and habitat