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Thick-billed Grasswren (Amytornis modestus)

The Thick-billed Grasswren is a small, mostly sedentary bird of chenopod shrublands in arid and semi-arid inland Australia. On development sites, it is most likely to occur in dense saltbush and bluebush vegetation along drainage lines, run-on areas, broad alluvial plains and other locations that have not been heavily disturbed. Clearing, fragmentation, grazing, altered water regimes, pollution and disturbance during breeding can affect local populations.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

New South Wales, Biodiversity Conservation Act 2016: Critically endangered.

Northern Territory, Territory Parks and Wildlife Conservation Act 1976: Critically endangered.

Breeding season

The species is generally sedentary and does not undertake a regular long-distance migration. Breeding is concentrated from late winter through spring, but rainfall can trigger breeding outside the main period.

Seasonal timing varies among populations and with rainfall. The month pattern is a practical guide based on the breeding records supplied, not a substitute for site-specific survey.

  • Breeding: Active nests have been recorded from late June to September. Breeding has also been reported in January and April after sufficient rainfall.
  • Young: Dependent young may be present during and shortly after the recorded nesting periods. The supplied documents do not give a precise fledging or dependency period.
  • Movement or dispersal: The species is sedentary or probably sedentary. Pairs may occupy the same home range throughout the year, and no regular migration is documented.
  • Highest clearing risk: Risk is highest during the main nesting period from June to September and can also increase from January to April after rainfall, when additional breeding may occur. Clearing should be preceded by targeted surveys and nest checks.

Identification

The Thick-billed Grasswren is a small, long-tailed ground bird that usually stays within dense low shrub cover. It is cryptic and can be difficult to detect unless observers move slowly through suitable chenopod vegetation.

Adults are about 15 to 20 cm long. The upperparts are dull brown, the underparts are paler fawn, and the feathers have fine white streaks. The bill and feet are dark grey and the eyes are dark brown.

The female has a chestnut patch on each side of the lower breast or flanks. Plumage varies among subspecies. The Flinders Ranges form, Amytornis modestus raglessi, is generally pale and lightly streaked, with a somewhat longer tail than the north-western form.

Length: 15 to 20 cm

Recorded mass: 17 to 20 g

Typical plumage: Dull brown above, paler fawn below, with white streaking

Identification: Similar species

Within its range, it may be confused with Eyrean Grasswren, Amytornis goyderi, and short-tailed grasswrens. The survey guidance also identifies the Striated Grasswren and short-tailed Amytornis species as possible confusion species in some regions.

The Thick-billed Grasswren is distinguished from the closely related Western Grasswren by its lighter body colour and heavier bill. Subspecies can differ in tail length, bill proportions, plumage tone and the strength of underpart streaking, so regional reference material and photographs should be used during field assessments.

  • Check the bill shape, tail length, body colour and degree of white streaking.
  • Treat a small, pale grasswren in dense chenopod shrubland as a possible Thick-billed Grasswren until it is identified with confidence.
  • Record the location, habitat, photographs and call description for all uncertain sightings.

Identification: Field signs and detection

The species is furtive and usually moves through low, dense vegetation close to the ground. It may briefly climb to a vantage point before disappearing back into cover.

The call is soft and high pitched, and can be difficult to hear in windy conditions. Birds are usually seen singly, in pairs or in small groups. The species feeds on the ground, so repeated movement through narrow gaps in dense shrub cover can be a useful visual clue.

Nests are semi-dome structures made from twigs, grasses and fibres. They are usually built within the foliage of a saltbush or bluebush shrub. No reliable species-specific tracks or scats are described in the supplied documents.

  • Search suitable habitat early in the morning, when birds are more active and vocal.
  • Use slow area searches and transects, listening for soft calls and watching the base and interior of shrubs.
  • Use call playback only under an approved survey method and avoid repeated playback near active nests.
  • Inspect dense saltbush and bluebush foliage for semi-dome nests before clearing.

Distribution: States and bioregional range

The species formerly occupied a broad area of arid and semi-arid southern Australia, but its distribution is now fragmented among regional populations and subspecies. Records and conservation information are concentrated in South Australia, the Northern Territory and western New South Wales.

In South Australia, the species occurs across inland chenopod shrublands, including the Lake Eyre basin, the North Flinders Ranges and the southern Lake Frome basin. The Flinders Ranges subspecies, A. m. raglessi, occurs around the North Flinders Ranges periphery and was recorded near the former Leigh Creek mine.

The north-western form, A. m. indulkana, occurs in drainage systems flowing towards Lake Eyre and extends to the Stuart Shelf and western Lake Torrens basin. In the Northern Territory, a small population was recorded near Charlotte Waters along drainage lines.

The species has also been recorded in western New South Wales. The Grey Range population, A. m. obscurior, was rediscovered in 2008 after being considered extinct and is described as a tiny, highly endangered population. The MacDonnell Ranges form in the Northern Territory has not been recorded since 1936 and is considered extinct.

  • South Australia: Lake Eyre basin, North Flinders Ranges, southern Lake Frome basin, western Lake Torrens basin and adjacent stony rangelands.
  • Northern Territory: Finke drainage formerly, and a small surviving population near Charlotte Waters.
  • New South Wales: western inland areas, including the Grey Range region.

Distribution: Known strongholds and subpopulations

The Leigh Creek area supports the Flinders Ranges subspecies, A. m. raglessi. Records and suitable habitat occur within the wider PEL 650 area, particularly along major drainage lines and broad alluvial plains with dense spiny shrubs. The Australian Government considered this population important for maintaining genetic diversity.

The north-western Northern Territory population is concentrated near Charlotte Waters. Surveys identified birds at four sites within an area of about 25 km², although the available assessment treated the area as one small population.

Other recognised populations include A. m. indulkana in inland South Australia, A. m. curnamona around the southern Lake Frome basin, A. m. obscurior in western New South Wales, and the restricted Cowarie population in the Sturt Stony Desert.

  • Prioritise surveys along drainage lines, run-on areas and broad alluvial plains with intact chenopod shrub cover.
  • Do not assume that highly disturbed mine or infrastructure areas are unsuitable without checking nearby intact habitat and connected drainage vegetation.
  • Map each observation and retain records at the subspecies or regional form level where this can be determined.

Distribution: Population size and trend

Population size is not known for the species as a whole. Several subspecies have very small or extinct populations, and the species has contracted from its former range.

The Northern Territory population near Charlotte Waters is estimated at fewer than 50 mature individuals. The restricted Cowarie population in South Australia was estimated at fewer than 1,000 mature individuals, based on an estimated density of about four adults per km² and an estimated area of occupancy of less than 60 km².

Two subspecies, A. m. modestus and A. m. inexpectatus, are extinct. The north-western form has declined to a highly fragmented population, while the western New South Wales form is described as Critically Endangered.

Northern Territory population: Fewer than 50 mature individuals, recorded at four sites within about 25 km²

Cowarie population: Probably fewer than 1,000 mature individuals

Cowarie estimated density: About four adults per km²

Cowarie estimated area of occupancy: Less than 60 km²

Habitat: Vegetation communities

Thick-billed Grasswrens depend on low, dense chenopod shrublands, especially where shrubs form continuous cover close to the ground. Habitat is often associated with drainage lines, run-on areas, stony plains and broad alluvial plains.

The species is almost entirely associated with chenopod low shrublands. Important plant groups include saltbushes, Atriplex species, and bluebushes, Maireana species.

The Flinders Ranges form uses low shrublands dominated by Blackbush, Maireana pyramidata, and less frequently Low Bluebush, Maireana astrotricha. Other regional habitats include Cottonbush, Maireana aphylla, Old-man Saltbush, Atriplex nummularia, Spiny Saltbush and related chenopod communities.

Some populations use shrublands with scattered low trees or shrubs, including western myall, black oak, Australian boxthorn, bullock bush and sugarwood.

Habitat: Key structural features

The most suitable habitat has dense stands of spiny shrubs that provide continuous cover at ground level and through the lower shrub layer. Drainage lines and run-on areas can support especially dense saltbush or bluebush growth.

At Leigh Creek, suitable habitat was concentrated along major drainage lines and broad alluvial plains in areas not previously disturbed by mining. The project footprint itself was highly disturbed, but suitable habitat occurred in the surrounding area.

  • Retain intact chenopod shrub cover along drainage lines and broad alluvial plains.
  • Map dense shrub patches separately from sparsely vegetated ground, even where both occur within the same vegetation community.
  • Avoid widening access tracks through continuous shrub cover where an alternative route is available.
  • Treat habitat beside drainage lines as potentially occupied until targeted surveys demonstrate otherwise.

Habitat: Climate and elevation

The species occurs in arid and semi-arid inland Australia. The supplied documents do not provide a reliable elevation limit. Habitat is associated more clearly with regional drainage, run-on and shrubland structure than with a stated elevation range.

Foraging habitat: Food and feeding locations

The Thick-billed Grasswren feeds on the ground within dense chenopod shrubland. Available information identifies seeds and invertebrates as the main food types, but does not provide a complete species-specific diet.

Birds feed on the ground, taking seeds and invertebrates among saltbush, bluebush and other low chenopod shrubs. The dense shrub layer provides feeding cover as birds move through the vegetation.

The species is usually encountered singly, in pairs or in small groups. The north-western form is sedentary, so feeding habitat is likely to remain within or close to the pair's occupied area.

  • Search the ground and lower shrub layer within dense Atriplex and Maireana communities.
  • Retain leaf litter, low branches and inter-shrub spaces where they form part of the ground-foraging habitat.
  • Avoid disturbing drainage-line shrubland solely because no birds are visible during a brief inspection.

Foraging habitat: Foraging range

Pairs of the north-western subspecies usually occupy home ranges of 20 to 40 ha. The eastern form has been reported to keep to the same 4 to 5 ha throughout the year, although the source of that estimate is identified as uncertain in the survey guidance.

The species is described as sedentary or probably sedentary. Construction impacts can therefore remove feeding habitat from an established home range even where birds do not disperse from the site.

North-western subspecies home range: Usually 20 to 40 ha per pair

Eastern form reported home range: 4 to 5 ha per pair, occupied throughout the year

Breeding habitat: Breeding biology

Breeding occurs within dense chenopod shrubland, where shrubs provide concealed nesting sites and nearby ground-foraging habitat. Breeding may be linked to seasonal rainfall in some populations.

The nest is usually a semi-dome made from twigs, grasses and fibres. It is built within the foliage of a shrub, usually a bluebush or saltbush.

Active nests have been recorded from late June to September. Breeding has also been reported in January and April after sufficient rainfall, and a second brood in a year has been suggested. The supplied documents do not provide reliable information on age at maturity, incubation period, fledging period or lifespan.

Breeding season: Usually spring to summer; active nests recorded from late June to September, with additional breeding reported from January to April after rainfall

Clutch size: Two to three eggs

Nest type: Semi-dome of twigs, grasses and fibres

Nest placement: Within foliage of a saltbush or bluebush shrub

Incubation: Not stated in the supplied documents

Age at maturity: Not stated in the supplied documents

Lifespan: Not stated in the supplied documents

Breeding habitat: Habitat needed for breeding

Breeding habitat requires dense, low chenopod vegetation with foliage suitable for concealing a semi-dome nest. Saltbush and bluebush stands along drainage lines and run-on areas can provide both nest sites and nearby feeding cover.

Before clearing, inspect dense shrubs at ground level and within the lower foliage. A bird that is absent during a daytime inspection may still have an active nest in the work area.

  • Mark dense saltbush and bluebush patches for pre-clearance inspection.
  • Inspect proposed clearing areas during the breeding period and after substantial rainfall when additional nesting may occur.
  • Establish no-go areas around active nests in accordance with the project approval and fauna handling procedure.
  • Do not remove nest-bearing shrubs until the relevant environmental representative has confirmed the required controls.

Sheltering habitat: Ground cover and shrub refuges

The species shelters within dense shrub cover rather than using documented tree hollows, burrows or caves. Its main refuge is the low, spiny chenopod layer, which also provides concealment from predators and people.

Birds move through dense saltbush, bluebush and related chenopod vegetation close to the ground. They are furtive, often disappearing rapidly into cover after a brief view.

Suitable shelter occurs particularly along drainage lines, run-on areas, broad alluvial plains and stony rangelands where shrub cover remains dense. The supplied documents do not identify a specific refuge size, roost tree, hollow, burrow or den used by the species.

  • Retain connected patches of dense low shrub cover around drainage lines and construction margins.
  • Avoid stockpiling materials, parking vehicles or placing spoil on dense chenopod refuges.
  • Keep temporary fencing, lighting and access routes outside intact shrub patches where practicable.
  • Inspect dense shrubs before slashing, grading or vehicle access.

Sheltering habitat: Handling and relocation

The supplied documents do not provide a species-specific capture, relocation or refuge construction method. If a bird is trapped or injured during works, follow the approved fauna management plan and use an appropriately experienced wildlife carer or ecologist.

  • Stop work if a bird is injured, trapped or repeatedly flushed from a small clearing area.
  • Record the exact location and habitat condition before any fauna handling.
  • Do not construct artificial nest sites or release birds into unsuitable shrubland without an approved method.

Threats: Clearing and fragmentation

The main risks on development sites are removal and fragmentation of chenopod shrubland, disturbance of occupied habitat, grazing and changes to water quality or drainage. Small regional populations are particularly sensitive to loss of habitat and declining habitat condition.

Clearing of dense chenopod shrubland can remove feeding, sheltering and nesting habitat. Fragmentation is a concern because the species is sedentary, occupies established home ranges and can occur in small, isolated populations.

At Leigh Creek, the former mine footprint was highly disturbed and direct habitat loss within the project area was considered unlikely to be significant because preferred habitat was absent there. Suitable habitat and records occurred in the surrounding PEL 650 area, particularly along drainage lines and broad alluvial plains.

  • Avoid clearing intact saltbush and bluebush shrubland, especially along drainage lines and broad alluvial plains.
  • Use existing disturbed areas for compounds, access tracks and laydown areas where practicable.
  • Map habitat outside the direct footprint because indirect effects can extend into nearby occupied areas.
  • Retain links between shrub patches rather than creating isolated remnants.

Threats: Grazing, watering points and drought

High stocking rates, severe drought and increased cattle activity can reduce shrub cover and habitat quality. In the Northern Territory, concern was raised about expansion of watering points and associated increases in cattle use within Atriplex nummularia habitat.

The evidence for the specific role of artificial watering points is not conclusive across the species. However, grazing, resource concentration around water and habitat degradation should be considered when assessing nearby pastoral or infrastructure activities.

  • Prevent construction activities from creating new cattle access to intact shrubland.
  • Manage temporary water points so they do not concentrate stock in occupied habitat.
  • Inspect fencing and gates for changes that could redirect stock into drainage-line shrubland.
  • Record drought-related loss of shrub cover as a cumulative impact.

Threats: Water, pollution and air emissions

Changes to groundwater or surface-water connections, contamination and altered drainage can degrade shrubland used by the species. The Australian Government identified potential indirect impacts at Leigh Creek from water contamination, air pollution, routine and fugitive gas emissions, poisoning and bioaccumulation.

Ground and surface-water impacts may affect habitat even where no vegetation is cleared directly. This is particularly relevant where works occur near drainage lines, alluvial plains, groundwater-dependent vegetation or artificial water points.

  • Maintain drainage patterns and avoid concentrating runoff onto occupied shrubland.
  • Prevent sediment, hydrocarbons, chemicals and contaminated water from entering drainage lines or run-on areas.
  • Monitor vegetation condition where a project may alter groundwater levels or water quality.
  • Assess routine and fugitive emissions where they may affect nearby habitat.

Threats: Fire, predators and other pressures

Land clearance, fire and introduced predators are identified among the broader pressures associated with decline in arid and semi-arid rangelands. The supplied documents do not establish a single species-specific fire regime or quantify predator impacts for Thick-billed Grasswrens.

Artificial watering points can benefit introduced foxes and feral cats by increasing water or prey availability in arid areas. Predation risk may therefore increase around concentrated water and food resources.

  • Do not use unplanned fire or burn dense chenopod habitat as a construction measure.
  • Manage food waste and carcasses around camps so they do not attract foxes or feral cats.
  • Avoid creating permanent artificial water sources close to occupied shrubland unless they are required and assessed.
  • Include fire, predator access and cumulative grazing pressure in the site risk assessment.

Threats: Survey and construction risk

The species is difficult to detect, especially in windy conditions and during the middle of the day. An absence of sightings during a brief inspection is not evidence that a habitat patch is unoccupied.

For areas less than 50 ha, the national survey guidance recommends 15 hours over 3 days for area searches or transects, 15 hours over 3 days for broadcast surveys and, where suitable, 15 hours over 3 days for mist-netting. Area searches should be conducted early in the morning, and playback is expected to be most effective during breeding.

Area searches or transects: 15 hours over 3 days for areas less than 50 ha

Broadcast surveys: 15 hours over 3 days for areas less than 50 ha

Mist-netting: 15 hours over 3 days where suitable

  • Use targeted surveys before clearing in suitable chenopod habitat.
  • Survey early in the morning and include call detection as well as visual searches.
  • Use the recommended survey effort as a starting point, then adjust it to habitat extent, season, access and project risk.
  • Apply the precautionary principle where suitable habitat is present but survey coverage is inadequate.

Survey methodology: 1. Area searches and transects

Survey the Thick-billed Grasswren in chenopod shrublands, especially dense saltbush and bluebush along drainage lines, run-on areas and broad alluvial plains. The species is furtive, usually sedentary and difficult to detect, so absence should not be assumed without suitable survey effort.

Search suitable habitat on foot during the early morning, when birds are most active and vocal.

Use sightings and calls to detect birds, and search slowly through dense, low chenopod cover.

The species is usually seen singly, in pairs or in small groups, and may briefly climb to a vantage point before disappearing into cover.

Use the survey guideline effort of 15 hours over 3 days for areas smaller than 50 hectares.

Record the search route, survey hours, weather, wind, rainfall, observers, habitat condition and all detections.

Preferred habitat: Chenopod shrublands, particularly saltbush Atriplex species and bluebush Maireana species, including drainage lines, run-on areas and broad alluvial plains

Recommended timing: Early morning

Minimum guideline effort: 15 hours over 3 days for areas smaller than 50 hectares

Survey methodology: 2. Broadcast surveys

Use broadcast surveys in suitable dense shrubland, particularly during the breeding season when territorial responses may be stronger.

Conduct the survey during the early morning and listen carefully for a soft, high-pitched call that can be difficult to hear in windy conditions.

Use the survey guideline effort of 15 hours over 3 days for areas smaller than 50 hectares.

Keep a record of broadcast locations, timing, call sequence, volume, weather, wind and any visual or auditory response.

Do not treat a non-response as evidence of absence, especially in windy conditions or degraded, fragmented habitat.

Recommended timing: Early morning, with particular value during the breeding season

Minimum guideline effort: 15 hours over 3 days for areas smaller than 50 hectares

Detection note: The call is soft and high-pitched, and may be difficult to hear in wind

Survey methodology: 3. Mist-netting where appropriate

Use mist-netting only where it is safe, lawful and necessary to supplement searches and broadcast surveys in low, dense vegetation.

Set the bottom pocket of the net at ground level because the species is a ground-feeding bird that moves through low cover.

Maintain continuous supervision and check nets at the frequency required by the relevant permit, animal ethics approval and state or territory guidance.

Use the survey guideline effort of 15 hours over 3 days for areas smaller than 50 hectares.

Restrict capture, handling and release to appropriately authorised personnel.

Recommended habitat: Low, dense vegetation

Minimum guideline effort: 15 hours over 3 days for areas smaller than 50 hectares

Handling requirement: Use appropriately authorised personnel and comply with permit and animal welfare requirements

Survey methodology: Minimum effort and reporting

  • Complete a habitat assessment before deciding that a site is unsuitable, including drainage lines, run-on areas, broad alluvial plains and dense chenopod shrubland.
  • Use the guideline effort of 15 hours over 3 days for area searches, broadcast surveys and, where used, mist-netting in areas smaller than 50 hectares.
  • Survey in suitable weather, avoid strong wind where possible, and document any departures from the guideline effort and the reason for them.
  • Map all records with coordinates, date, time, detection method, number of birds, behaviour, photographs or recordings where available, and the associated habitat.
  • Submit confirmed records and negative survey results, where requested, to the relevant state or territory wildlife database and the Australian Government species information system.
  • Report the subspecies or regional form where it can be identified reliably, because the species includes geographically distinct populations and subspecies.

Before habitat disturbance: Avoid and minimise

Treat occupied or suitable chenopod shrubland as a potential habitat constraint before clearing or construction. The Flinders Ranges population near Leigh Creek was considered important for maintaining genetic diversity, and habitat outside disturbed mine areas supported dense shrub cover along drainage lines and alluvial plains.

  • Avoid clearing dense saltbush and bluebush shrubland, particularly along drainage lines, run-on areas and broad alluvial plains.
  • Retain continuous blocks of low chenopod cover and avoid creating gaps between retained habitat patches.
  • Keep machinery, laydown areas, access tracks, spoil and stockpiles out of retained shrubland and drainage lines.
  • Maintain natural drainage and prevent sediment, pollutants and contaminated water from entering retained habitat.
  • Do not rely on the absence of birds from a highly disturbed footprint to rule out indirect effects on nearby habitat.

Before habitat disturbance: Approvals and work planning

National status: Vulnerable under the EPBC Act

Breeding period identified in the survey guideline: June to September, with possible breeding in January and April after sufficient rainfall

State listings provided for this profile: Critically Endangered in New South Wales and the Northern Territory

  • Check whether the action may significantly affect the EPBC Act listed species and refer the action if required before starting controlled works.
  • Obtain the relevant state or territory approvals, wildlife permits and scientific or animal ethics approvals before surveying, capturing, handling or relocating birds.
  • Confirm the applicable state listing and conservation requirements for the work area, including the critically endangered state listings identified for New South Wales and the Northern Territory.
  • Schedule clearing outside the main breeding period of June to September where practicable, and reassess timing after substantial rainfall because breeding can also occur in January and April when conditions are suitable.
  • Prepare a fauna management plan that identifies habitat, survey effort, exclusion areas, authorised personnel, stop-work triggers, injured animal procedures and reporting requirements.

Before habitat disturbance: Site preparation

  • Complete the pre-clearance survey using suitable early morning searches and broadcast surveys before vegetation disturbance.
  • Mark retained chenopod shrubland, drainage lines, run-on areas and all no-go areas on approved plans and on the ground.
  • Install exclusion fencing where it can prevent machinery and workers entering retained habitat, and inspect the fencing before and during works.
  • Brief all workers on the species' appearance, quiet call, habitat, exclusion areas, stop-work triggers and reporting chain.
  • Plan access routes so vehicles do not drive through dense shrub cover or across drainage lines.

During habitat disturbance: Daily controls

Use a controlled clearing sequence that gives birds a chance to move into retained habitat. The species is a small, ground-feeding bird that can remain hidden in dense shrub cover, so visual checks alone are not sufficient.

  • Inspect exclusion fencing, signs and no-go areas before work starts each day.
  • Use a fauna spotter catcher during vegetation clearing and any activity that can disturb suitable chenopod habitat.
  • Clear progressively towards retained habitat, where this is safe and consistent with the approved fauna management plan.
  • Keep machinery speeds low near retained shrubland and stop unnecessary engine noise during searches and fauna handling.
  • Stop work in suitable habitat during strong wind, poor visibility or other conditions that prevent effective detection and safe fauna handling.

During habitat disturbance: Spotter catcher and machinery

  • The fauna spotter catcher should inspect the next clearing section before machinery enters and maintain communication with the operator by radio or agreed hand signals.
  • Search dense shrub bases, drainage-line vegetation and ground cover before removing vegetation or placing machinery, materials or spoil.
  • Require the operator to stop immediately when the spotter catcher gives the agreed stop signal.
  • Do not allow unauthorised workers to chase, catch, handle or release a grasswren.
  • Record each clearance area, inspection time, personnel, weather, habitat condition, detection outcome and any fauna action taken.

During habitat disturbance: If a grasswren is found

  • Stop work and allow the bird to move without pursuit if it can leave the work area safely.
  • Keep people and machinery back and maintain a clear route to nearby retained habitat.
  • Use capture or handling only when authorised personnel determine that it is necessary to prevent injury or comply with an approved fauna management plan.
  • Release a captured bird into nearby retained habitat that matches its chenopod shrubland requirements, only where the release is approved and safe.
  • Do not move the bird to an unrelated habitat type or distant location without specific approval and ecological justification.
  • Take an injured bird to an appropriately qualified veterinarian or authorised wildlife carer as soon as practicable, and record the transfer.
  • Stop work and obtain advice from the project ecologist or relevant wildlife authority if the bird cannot be safely moved, if repeated birds are detected, or if an active nest or dependent young is found.

During habitat disturbance: Habitat features and stop-work triggers

  • Protect dense saltbush and bluebush cover, drainage-line vegetation, run-on areas and broad alluvial shrubland as the relevant habitat features for this species.
  • Do not remove logs, rocks, burrows or other ground features in suitable shrubland without checking the approved fauna management plan and state requirements.
  • Stop work for any confirmed Thick-billed Grasswren detection within the active clearing area until the spotter catcher and project ecologist agree on the response.
  • Stop work if clearing enters marked habitat, exclusion fencing fails, water or sediment moves into retained habitat, or a suspected nest or dependent young is found.
  • Escalate any chemical spill, dust event, smoke, air emission or contaminated-water incident that could affect retained habitat or nearby drainage lines.

After habitat disturbance: Post-clearance checks

Post-clearance work should confirm that the approved footprint was respected and that retained chenopod habitat remains connected and functional. Indirect effects, including water contamination and air pollution, were identified as potential risks for this species.

  • Inspect the cleared boundary and retained habitat immediately after each clearance stage for injured, trapped or isolated fauna.
  • Check exclusion fencing, drainage controls, erosion controls and access restrictions after rain and after heavy vehicle movements.
  • Remove waste, spoil and temporary materials from retained shrubland and drainage lines.
  • Confirm that no unauthorised clearing, vehicle damage, sediment deposition or chemical contamination has affected retained habitat.
  • Record all fauna observations, incidents, mortalities, injuries, relocations and corrective actions.

After habitat disturbance: Monitoring and reporting

  • Repeat early morning area searches and broadcast surveys in retained habitat where the approval or fauna management plan requires post-work monitoring.
  • Use the same search areas, methods and recording standards before and after the works so detection results can be compared.
  • Monitor retained drainage-line and alluvial shrubland for loss of dense cover, weed invasion, grazing pressure, erosion and altered water flow.
  • Report results, incidents, corrective actions and any new records to the project approval authority and the relevant state wildlife database.
  • Review controls if birds are detected in work areas, if habitat quality declines, or if water, dust or emissions affect retained habitat.

After habitat disturbance: Offsets and compliance close-out

  • Confirm whether the approval requires an offset, habitat restoration or another compensatory measure for unavoidable impacts.
  • Map the final disturbance footprint and the area and condition of retained or restored chenopod habitat.
  • Do not close the fauna management action until required monitoring, incident reporting, rehabilitation and offset commitments are documented.

Rehabilitation actions: Restore species habitat

Rehabilitation should recreate the low, dense chenopod structure used by the species rather than establishing a generic grass cover. Prioritise habitat along drainage lines, run-on areas and broad alluvial plains, while protecting restored areas from grazing and other pressures.

  • Use locally appropriate saltbush Atriplex species and bluebush Maireana species identified from the pre-clearing vegetation assessment.
  • Re-establish dense, low shrub cover with connected patches rather than isolated plantings.
  • Reinstate natural drainage and run-on patterns without concentrating flow through retained or restored shrubland.
  • Use locally sourced seed or propagation material where practicable and consistent with the approved rehabilitation plan.
  • Do not replace chenopod shrubland with irrigated pasture, lawn or a vegetation type that does not provide dense low cover.

Rehabilitation actions: Protect and manage restored areas

  • Fence or otherwise exclude stock from new plantings until plants are established and the rehabilitation area can support the required cover.
  • Control weeds and prevent rubbish, vehicle access and stockpiling in restored habitat.
  • Manage introduced predators and other threats in accordance with approved state, territory and project plans, without using unapproved poisons or control methods.
  • Plan fire management so fire does not remove connected chenopod cover across the restored area at the same time.
  • Avoid artificial watering points that could increase cattle use, predator activity or habitat degradation in restored grasswren habitat.

Rehabilitation actions: Monitor success

  • Inspect restored areas after establishment, after significant rainfall and at the monitoring intervals required by the approval.
  • Measure plant survival, chenopod cover, weed cover, erosion, drainage condition, grazing signs and connectivity with retained habitat.
  • Use early morning area searches and broadcast surveys to check whether Thick-billed Grasswrens use restored or retained habitat once vegetation provides suitable cover.
  • Set success measures around the return and persistence of dense, low chenopod shrub cover and the protection of functioning drainage-line and run-on habitat.
  • Submit rehabilitation monitoring results and all grasswren records to the relevant project authority and state wildlife database.

Sources