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Australasian Bittern (Botaurus poiciloptilus)

The Australasian Bittern is a large, secretive heron of freshwater wetlands, reedbeds, rushes and sedgelands across southern and eastern Australia. It is listed as Endangered under the EPBC Act and is sensitive to wetland clearing, altered water regimes, fire, grazing, predators and disturbance during breeding. Rice fields can also provide important habitat, particularly in the Riverina.

Conservation status

Commonwealth, EPBC Act 1999: Endangered.

Queensland, Nature Conservation Act 1992: Endangered.

New South Wales, Biodiversity Conservation Act 2016: Endangered.

Victoria, Flora and Fauna Guarantee Act 1988: Critically endangered.

South Australia, National Parks and Wildlife Act 1972: Endangered.

Western Australia, Biodiversity Conservation Act 2016: Endangered.

Australian Capital Territory, Nature Conservation Act 2014: Endangered.

Breeding season

Timing varies with rainfall, flooding, irrigation and local wetland conditions. The pattern below combines the regular breeding period with documented Western Australian calling and movement periods, and should be adjusted to local records and water levels.

Before clearing or construction, check current wetland water levels, vegetation condition, recent records and breeding calls. Seasonal timing is not a substitute for a site assessment because flooding and irrigation can shift breeding activity.

  • Breeding: Breeding is generally from October to February. In southern Western Australia, calling commonly occurs from September to December and peaks in October and November. Inland flooding can result in breeding outside the regular season.
  • Young: Young are expected in nests or dependent on adults during and after the breeding period. The species-specific incubation and fledging periods are not known in the supplied sources, so the full dependent-young period cannot be defined precisely.
  • Movement and dispersal: Outside breeding, birds may disperse between wetlands, move to drought refuges and form small groups. In Western Australia, some birds may use estuaries and south coast refuges from late summer to mid-winter. Movements of up to 600 km have been recorded in eastern Australia.
  • Highest clearing risk: Clearing, draining, burning or construction disturbance is most likely to harm the species from September to February because breeding, nesting and dependent young may occur. Risk can extend outside these months after flooding or where birds are using drought refuges.

Identification

Australasian Bitterns are large, stocky herons with strongly streaked brown and buff plumage. They are difficult to detect in dense wetland vegetation, so calls, flushed birds and careful searches of suitable reedbeds are important during project surveys.

Adults have a long, thick neck, a straight brownish yellow bill, yellow eyes, pale green legs and feet, and a pale eyebrow and throat. The upperparts are mottled dark brown, buff and black, while the underparts are streaked brown and buff.

When alarmed, a bird may freeze with its neck extended and bill pointing upwards. It can sway with the reeds and remain almost invisible. In flight it has broad wings, slow shallow wingbeats and dangling legs.

Length: Up to 76 cm

Wingspan: More than 1 m

Typical appearance: Heavy-set, thick-necked heron with mottled brown upperparts and streaked buff underparts

Identification: Calls and field signs

The male has a deep, resonant booming call during the breeding season. The call may carry more than 1 km in good weather and is the most useful detection method in dense vegetation.

Feeding platforms may be made from trampled reeds over deeper water and can contain prey remains. Nests are shallow platforms of broken reeds, sedges or sticks, usually 5 to 10 cm above the water surface.

  • Listen for repeated low booming calls from dense reed, rush or sedge beds, especially from September to December in southern Western Australia and from October to February across the broader range.
  • Inspect dense wetland vegetation for flattened reed platforms, prey remains and shallow nests, but avoid entering occupied reedbeds unless the survey method and approvals allow it.

Identification: Similar species and sex

The supplied sources list Nankeen Night-Heron, Striated Heron and Australian Little Bittern as species requiring comparison. They do not provide detailed diagnostic comparison characters for these species.

Australasian Bitterns are sexually dimorphic in behaviour during breeding, with the male producing the characteristic booming call. The supplied sources do not provide reliable plumage differences between adult males and females. Juveniles are described as much paler than adults.

  • Treat a large, cryptic heron in dense wetland cover as a possible Australasian Bittern until its size, structure, plumage and call are resolved.
  • Use photographs, audio recordings and an experienced ornithologist for confirmation where a sighting could affect clearing or construction decisions.

Distribution: National range

The species occurs mainly in southern, south-eastern and south-western Australia, with additional records in Queensland and Tasmania. It is widespread but uncommon, and its distribution is patchy because suitable wetlands are scattered and fluctuate with water availability.

The Australasian Bittern is recorded in Victoria, Tasmania, New South Wales, South Australia, Western Australia, Queensland and the Australian Capital Territory. It also occurs in New Zealand, but this profile concerns Australian project work.

In Australia, the documented range extends from south-eastern Queensland through eastern and southern Australia to Tasmania and south-western Western Australia. It occurs in coastal and sub-coastal areas, the Murray-Darling Basin, south-eastern South Australia and the eastern Tasmanian marshes.

  • Relevant Australian states and territories are ACT, NSW, Queensland, South Australia, Victoria, Western Australia and Tasmania.
  • The species may occur in freshwater wetlands, rice fields and brackish estuaries within its range.

Distribution: Bioregions and strongholds

NSW records or predicted habitat span many IBRA regions, including the Riverina, Darling Riverine Plains, Murray Darling Depression, South Eastern Highlands, South East Corner, Sydney Basin, NSW North Coast, NSW South Western Slopes, Cobar Peneplain, Mulga Lands, Nandewar, New England Tablelands and Brigalow Belt South.

In Western Australia, the recovery plan identifies the Swan Coastal Plain, Jarrah Forest, Warren and Esperance Plains IBRA regions. The Muir-Unicup system and south coast wetlands are the current Western Australian strongholds.

  • The largest known nesting population is in irrigated rice fields in the Riverina.
  • Important Western Australian wetland suites include Muir-Unicup, Lake Pleasant View and the Mount Manypeaks wetlands, Cape le Grand wetlands, Benger Swamp, Vasse-Wonnerup, the Gingilup, Quitchup and Jasper wetlands, Lake Maringup, Boat Harbour and Owingup wetlands, and the Moates Lake suite.
  • Historical or recent Western Australian locations include Forrestdale Lake, James Swamp, Thomsons Lake, Benger Swamp, Lake Qualeup, Vasse-Wonnerup and wetlands from Augusta to Cape Arid.

Distribution: Population and trend

The species is difficult to count because it is cryptic, dispersed and often detected by male calls rather than direct sightings. The Western Australian population was estimated at fewer than 150 mature individuals, with an estimate of 38 to 154 in 2009 to 2010.

The Western Australian population was estimated to have declined by 25 to 50 percent between the 1980s and 2010. The global population was assumed to be fewer than 2,500 mature individuals in the recovery plan.

Western Australian population: Estimated 38 to 154 individuals in 2009 to 2010, with fewer than 150 mature individuals stated in the recovery plan

Western Australian trend: Estimated decline of 25 to 50 percent between the 1980s and 2010

Global population estimate: Fewer than 2,500 mature individuals

Habitat: Wetland types

Australasian Bitterns require wetlands with water and dense emergent vegetation. Habitat suitability depends on both the wetland itself and the local catchment that maintains its surface water or groundwater.

The species uses permanent and semi-permanent freshwater wetlands with dense beds of reeds, rushes, sedges, bullrushes and cutting grass. It can also use moderately brackish wetlands and estuarine areas with suitable emergent cover.

Australian rice fields provide extensive artificial wetland habitat. Irrigated rice fields can offer more reliable water than some natural wetlands, and the Riverina supports the largest known nesting population.

  • Assess natural swamps, marshes, reedbeds, sedgelands, floodplain wetlands, rice fields and suitable brackish estuaries for potential use.
  • Include adjacent areas and the local surface water and groundwater catchment in habitat assessment where they maintain wetland water levels.

Habitat: Vegetation and structure

Preferred vegetation includes rushes, reeds and sedges, particularly Baumea, Gahnia, Typha, Eleocharis and low fine sedges. Melaleuca shrubs can also be associated with breeding habitat.

Foraging habitat generally has shallow water, less than 30 cm deep, with low to medium density water plants mixed with or near short fine sedges. Nesting habitat has denser emergent vegetation.

  • Retain intact reed, rush and sedge beds, including their wetland edges and hydrological connections.
  • Map areas of shallow water, dense emergent vegetation and open movement channels through the vegetation.
  • Avoid assuming that open water alone is suitable habitat. The species depends on the structure and cover provided by wetland plants.

Habitat: Climate and elevation

The supplied sources describe occurrence from south-eastern Queensland to Tasmania and south-western Western Australia, including coastal, sub-coastal and inland wetland systems. They do not provide a species-specific elevation limit.

Wetland suitability varies with rainfall, flooding, irrigation and groundwater. Drought can reduce habitat availability and increase the importance of permanent wetlands and other drought refuges.

Elevation limit: Not specified in the supplied sources

Water conditions: Western Australian critical habitat includes fresh to moderately brackish wetlands with pH 5.5 to 8.5

Foraging habitat: Diet

Australasian Bitterns forage mainly at night in shallow wetland water and among emergent vegetation. They use waiting, slow stalking and active pursuit to capture prey.

The diet includes fish, frogs, yabbies, snails, insects, spiders, other invertebrates, mice, small birds and small reptiles. Available prey varies with water depth, wetland condition and vegetation structure.

The bird may use wing and leg movements to confuse or attract prey. Feeding platforms constructed from trampled reeds over deeper water may contain prey remains.

Foraging period: Mainly at night

Recorded prey: Fish, frogs, yabbies, snails, insects, spiders, mice, small birds and small reptiles

  • Search for feeding platforms and prey remains in reedbeds where direct observations are unlikely.
  • Treat shallow water with abundant aquatic and terrestrial prey as potential foraging habitat, even where no birds are detected during daytime searches.

Foraging habitat: Foraging structure and movements

In Western Australia, preferred foraging areas have water less than 30 cm deep, low to medium density water plants and short fine sedges. Dense vegetation is needed nearby for concealment and nesting.

Individuals can move between wetlands when local water conditions change. Satellite tracking in eastern Australia recorded movements of up to 600 km between otherwise separate wetlands outside the breeding season.

Preferred foraging depth in WA: Less than 30 cm

Recorded movement distance: Up to 600 km between wetlands outside the breeding season

  • Retain shallow wetland margins, low fine sedges and connected reed and rush cover.
  • Consider nearby wetlands and possible movement routes when assessing a project that could remove or isolate a wetland.
  • Do not define the foraging area only by the wetland footprint. Hydrological changes in the local catchment can alter water depth and prey availability.

Breeding habitat: Breeding biology

Breeding occurs in dense wetland vegetation when water conditions are suitable. Males call to attract mates and defend territory, while nests are placed close to or above shallow water.

Australasian Bitterns usually breed in summer, although inland flooding can trigger breeding outside the regular season. In southern Western Australia, calling usually follows peak wetland water levels and is concentrated from September to December, with peak calling in October and November.

Nests are shallow platforms in dense reeds, rushes or sedges. In Western Australia they are approximately 30 to 40 cm in diameter and are built about 5 to 10 cm above the water.

Typical breeding season: October to February across the broader range; October to January in NSW; September to December in southern Western Australia

Peak male calling in southern WA: October and November

Clutch size: Usually 4 to 6 eggs. The Western Australian recovery plan gives 4 to 5 eggs.

Nest size: Approximately 30 to 40 cm in diameter

Nest height: Approximately 5 to 10 cm above water

Incubation and fledging: Not known for the Australasian Bittern. The WA plan states that incubation and fledging are likely to be similar to the Eurasian Bittern, but this is an extrapolation.

Age at maturity: Not specified for the Australasian Bittern in the supplied sources

Lifespan: Not specified as a direct species measurement. Estimated generation length is 5.5 years.

  • Treat booming males, occupied reedbeds and shallow nest platforms as breeding indicators.
  • Schedule vegetation clearing, earthworks, dewatering and high-noise activities outside the likely breeding period where practicable, or undertake targeted assessment and apply site-specific controls.

Breeding habitat: Habitat needed for breeding

Breeding habitat includes dense, relatively undisturbed beds of Baumea, Gahnia, Typha and other reeds and sedges, with shallow water and sufficient cover around the nest. Melaleuca shrubs may also be associated with nests.

Breeding wetlands need suitable water levels and a functioning local catchment. Water levels that fall too far can expose nests and increase fire risk, while excessive inflow or altered drainage can damage wetland vegetation.

  • Retain dense emergent vegetation and avoid trampling, grazing, burning or machinery access through likely nesting areas.
  • Protect wetland inflows, groundwater connections and adjacent habitat that support suitable water levels.
  • Use call surveys during the breeding season because birds may remain hidden even where breeding habitat is occupied.

Sheltering habitat: Day shelter and concealment

The species relies on dense wetland vegetation for concealment, daytime shelter and protection from predators. It does not use tree hollows, dens or burrows according to the supplied sources.

During the day, Australasian Bitterns hide in dense reeds or rushes. When disturbed, they freeze with the neck and bill raised, using their streaked plumage and the movement of surrounding vegetation as camouflage.

Suitable shelter includes dense beds of Baumea, Gahnia, Typha, Eleocharis, other rushes, sedges and reeds, with enough water and vegetation density for movement and concealment.

  • Retain continuous dense wetland cover around open water and shallow foraging areas.
  • Avoid clearing narrow strips through reedbeds unless the effect on cover, movement and nesting habitat has been assessed.
  • Check dense vegetation carefully before slashing, burning, draining or entering with machinery.

Sheltering habitat: Drought refuges and seasonal shelter

Permanent wetlands and estuarine or south coast wetlands can provide refuge when semi-permanent wetlands dry. In Western Australia, some birds may move to estuaries and south coast drought refuges from late summer to mid-winter.

During dry periods, birds can gather in the remaining wet portions of wetlands. Small groups of 8 to 10 birds have been recorded in a restricted area where water remained, although the species is usually solitary or found in pairs.

Recorded drought refuge aggregation: 8 to 10 birds in a remaining wet area at one Western Australian wetland

Typical social pattern: Usually solitary, occasionally in pairs, with dispersed aggregations of up to 12 birds reported

  • Protect remaining wet areas and dense vegetation during drought, including wetlands that are not occupied in every year.
  • Avoid assuming that an apparently dry or sparsely occupied wetland has no value. Suitable habitat can return after flooding or wet seasons.
  • Include connected wetlands and potential drought refuges in project impact assessments.

Threats: Clearing, fragmentation and hydrology

The main project risks are loss of wetland area, altered water regimes, damage to reed and sedge cover, fire, grazing, pollution and predation. Impacts can occur beyond the clearing footprint because wetland hydrology depends on the surrounding catchment.

Drainage, filling, clearing and urban development remove or degrade wetland habitat. Diversion of water, groundwater abstraction, reduced inflows, excessive runoff and altered drainage can change water depth and vegetation structure.

Wetland salinisation and acidification have caused loss of habitat in Western Australia. Habitat critical to survival includes occupied wetlands, adjacent suitable habitat, and the surface water or groundwater catchment that maintains them.

  • Avoid clearing reed, rush and sedge beds, shallow wetland margins and wetland connections.
  • Assess changes to inflow, groundwater, drainage, sediment movement, salinity and water depth, not only direct vegetation removal.
  • Maintain wetland refuges and nearby suitable habitat during drought and construction dewatering.
  • Protect rice field habitat and consult with land managers where irrigation or cropping changes could reduce habitat availability.

Threats: Fire, grazing and vegetation damage

Intense or frequent fire can remove the reed, rush and sedge cover used for shelter and breeding. Dry wetlands burn more readily, and Baumea habitat may take more than a decade to recover after fire.

Cattle, horses, deer, goats and pigs can trample nests, reduce cover and damage foraging habitat. Inappropriate grazing and frequent burning are also identified threats in NSW.

Potential Baumea recovery time after fire: More than 10 years

  • Exclude stock from occupied and potentially suitable wetlands where practicable.
  • Do not burn wetland vegetation during the breeding season or when nests or dependent young may be present.
  • Protect wetlands from construction ignition sources, hazard reduction burns and machinery damage.
  • Manage fire differently between wetlands because the appropriate regime depends on vegetation type and location.

Threats: Predators, pollution and disturbance

Foxes and feral cats are important introduced predators. Rats and pigs may also affect nests and young. Native predators include swamp harriers, rakali, bush rats, snakes and Australian Ravens.

Siltation, pollution, salinity, herbicides, pesticides and other chemicals near wetlands can reduce water quality, prey availability or wetland condition. Construction noise, movement and access through dense vegetation may disturb cryptic birds and expose nests.

  • Control foxes and feral cats near important wetlands using approved methods and site risk controls.
  • Prevent sediment, fuels, concrete washout, herbicides, pesticides and other pollutants from entering wetlands or drainage lines.
  • Fence or otherwise restrict access to breeding habitat during construction where disturbance cannot be avoided.
  • Use fauna spotter catchers experienced with cryptic wetland birds and stop work if a bird, nest or breeding call indicates an active impact area.

Survey methodology: 1. Nocturnal call surveys

Australasian Bitterns are secretive wetland birds that hide in dense reeds, rushes and sedges and are more readily detected by their deep booming calls than by daytime searches. Survey effort should focus on wetlands and associated catchments that may be affected by the project, including permanent, semi-permanent, freshwater and moderately brackish sites.

Survey after dark because Australasian Bitterns feed mainly at night and males call during the breeding season.

Use listening surveys during the main calling period, generally October to February, with September to December calling reported in southern Western Australia and peak calling in October and November there.

Listen from wetland edges and suitable vantage points for the distinctive deep booming call, which can carry more than 1 kilometre in good weather.

Give priority to dense stands of reeds, rushes and sedges, including Baumea, Typha, Gahnia and Eleocharis habitats, and record calls from all directions.

Reported breeding season: October to February

Reported southern WA calling period: September to December, peaking in October and November

Call distance reported in good weather: More than 1 kilometre

  • Record the date, start and finish time, weather, wind, observer position, wetland water level, vegetation type and the direction and estimated location of each call.
  • Do not treat the absence of a call on one visit as evidence that the species is absent, because calling and detectability vary with environmental conditions and birds are difficult to see.

Survey methodology: 2. Nocturnal wetland searches

Search suitable wetland margins and dense emergent vegetation after dark, when the species is mainly feeding.

Use quiet, slow searches from existing access routes or wetland edges where safe, with a torch used to scan shallow water and vegetation without entering unstable or sensitive wetland areas.

Look for birds standing or stalking in shallow water, feeding platforms made from trampled reeds, prey remains and movement through reedbeds.

Favoured foraging water depth in WA: Less than 30 centimetres

Typical adult length: Up to 76 centimetres

Typical wingspan: More than 1 metre

  • Search shallow water less than 30 centimetres deep where low to medium density vegetation occurs near short fine sedges, and inspect nearby denser vegetation suitable for nesting.
  • Record all observations, including birds, feathers, tracks, feeding platforms, nests and prey remains, with a mapped location and habitat description.
  • Avoid relying on spotlighting alone, because the species is highly camouflaged and may freeze with its neck and bill pointing upwards.

Survey methodology: 3. Daytime habitat and breeding inspection

Inspect the full wetland and its supporting catchment during daylight to map habitat that could be disturbed by clearing, drainage, access tracks, construction or changes to water levels.

Map dense reed, rush and sedge beds, shallow foraging areas, open water, wetland margins, adjacent potential habitat and drainage lines that maintain wetland inflows.

During the breeding period, inspect suitable vegetation for shallow nests built on platforms of bent reeds or sedges, generally 5 to 10 centimetres above the water in the Western Australian recovery plan.

Reported nest height in WA: Approximately 5 to 10 centimetres above water

Reported clutch size in WA: 4 to 5 eggs

Reported clutch size in NSW profile: Usually 6 eggs

  • Treat all wetlands known to support the species, wetlands that are regularly occupied, adjacent similar habitat, the local surface and groundwater catchment, and suitable undiscovered habitat as survey areas where relevant.
  • Do not enter dense nesting vegetation unless the work is authorised, necessary and controlled by the fauna management plan.
  • Record water depth, salinity or visible water quality issues, vegetation structure, fire history, grazing or trampling, weeds and evidence of foxes, cats, pigs or other predators.

Survey methodology: 4. Seasonal and follow-up surveys

Plan repeat surveys across suitable water conditions because Australasian Bitterns may use permanent wetlands, semi-permanent wetlands, rice fields and drought refuges at different times.

Include follow-up surveys after rainfall or changes in wetland water levels where this is safe and relevant, because birds may move between wetlands and can travel up to 600 kilometres between otherwise separate wetlands outside the breeding season.

Survey both the proposed impact area and nearby retained wetlands that could receive displaced birds.

Recorded movement between wetlands: Up to 600 kilometres outside the breeding season

Western Australian population estimate: Fewer than 150 mature individuals, based on estimates ranging from 38 to 154

  • Increase survey coverage where the wetland is drying, where dense habitat is fragmented, or where construction may alter inflows, groundwater, drainage or environmental water delivery.
  • Use the same listening points and observation routes on repeat visits so that changes in occupancy and habitat condition can be compared.
  • There is no species-specific survey effort, such as a prescribed number of nights or transect length, in the supplied documents, so document the rationale, coverage and limitations of the effort used.

Survey methodology: Minimum effort and reporting

  • Survey every wetland, reedbed, rushbed, sedgeland, rice field, wetland margin and supporting drainage area that may be cleared, filled, dewatered, burned, polluted or otherwise disturbed.
  • Use nocturnal call and visual searches, together with daytime habitat and nest inspections, and repeat the work when initial conditions are unsuitable or the project could affect wetland hydrology.
  • Record survey dates, times, observers, methods, weather, water conditions, habitat, effort, detection results, photographs, mapped locations and any constraints on access or visibility.
  • Have a suitably experienced wetland bird ecologist review negative results where habitat is suitable or the project could affect a known or potential wetland refuge.
  • Submit confirmed and significant incidental records to the relevant state wildlife database and provide records through the project approval and environmental reporting systems.
  • Retain the survey data and spatial layers with the project environmental records so that future monitoring and compliance checks can use the same locations.

Before habitat disturbance: Avoid and minimise habitat loss

Avoid disturbance to wetlands and their hydrology wherever possible. The species depends on dense emergent vegetation, shallow foraging water, nesting cover and wetland catchments, and may use artificial wetlands such as rice fields when natural habitat is unavailable.

  • Redesign the project to retain wetlands known to support Australasian Bitterns, dense reed, rush and sedge beds, shallow foraging areas, wetland margins and adjacent potential habitat.
  • Avoid drainage, filling, diversion of inflows, groundwater abstraction, altered water levels, pollution, sedimentation and construction activities that could change wetland salinity, acidity or water quality.
  • Retain connectivity between occupied wetlands, nearby seasonal wetlands and drought refuges because birds can disperse between otherwise separate wetlands.
  • Keep project infrastructure and access routes outside wetland catchments where practicable, and prevent works from severing surface water or groundwater processes that maintain habitat.

Before habitat disturbance: Check approvals and plan the works

National listing: EPBC Act Endangered

States and territories identified in the supplied records: ACT, NSW, Queensland, South Australia, Victoria and Western Australia

  • Check whether the proposed action is likely to have a significant impact on this EPBC Act Endangered species and obtain project-specific Commonwealth advice or referral decisions before work starts.
  • Check the current threatened species, wildlife, clearing, wetland, waterway and fire requirements in every state or territory where the project occurs.
  • Obtain any required wildlife, animal ethics, handling, relocation, clearing, dewatering and rehabilitation approvals before appointing the fauna spotter catcher.
  • Prepare a fauna management plan that identifies habitat, survey findings, exclusion zones, wetland protection measures, roles, stop-work triggers, handling arrangements, incident contacts and reporting requirements.
  • Stage works to avoid the main breeding and calling period where the project could disturb nesting vegetation, and obtain ecological advice before working during October to February or during local peak calling periods.

Before habitat disturbance: Prepare and mark the site

  • Complete the pre-clearance survey before machinery enters the site, including a mapped inspection of all wetlands, dense emergent vegetation, shallow water and supporting drainage areas.
  • Mark no-go areas around wetlands, nests, calling locations and retained vegetation, and show them on construction plans and daily pre-start maps.
  • Install exclusion fencing where it can prevent machinery, vehicles, stock and people from entering retained wetland habitat without blocking necessary water movement or bird movement.
  • Brief all workers that this is a cryptic, threatened wetland bird and that a bird may be present even when it is not visible.
  • Confirm safe access, emergency response, dewatering controls, sediment controls, spill response and arrangements for an authorised fauna handler before starting.

During habitat disturbance: Daily controls and spotter catcher duties

Keep machinery away from retained wetland habitat and maintain a direct link between the operator, supervisor and authorised fauna spotter catcher. Stop work when an Australasian Bittern, nest or unexpected wetland habitat is found in the impact area.

  • Inspect exclusion fencing, no-go markers, sediment controls, drainage controls and wetland water levels before each shift and after heavy rain or an incident.
  • Position the fauna spotter catcher where they can see the active work area, retained habitat and machinery movement, and maintain reliable communication with the operator and supervisor.
  • Use a slow, staged work sequence around reedbeds, rushes, sedges, shallow water and wetland margins, with the spotter catcher able to stop machinery immediately.
  • Prevent workers, vehicles, spoil, fuels, concrete washout, sediment and waste from entering wetlands or their inflow areas.
  • Do not burn, slash or mechanically clear wetland vegetation unless the action is approved, assessed and supervised under the fauna management plan.

During habitat disturbance: If a bittern or nest is found

  • Stop the machine and all activity that could approach, trap, injure or disturb the bird, nest or young.
  • Keep people, vehicles and dogs away, reduce noise, and allow the bird to remain in cover unless an authorised handler determines that intervention is necessary.
  • Do not chase, corner, catch or relocate the bird without the required wildlife authority, training and project approval.
  • Have the fauna spotter catcher notify the site supervisor and project ecologist, record the location and condition, and establish an exclusion area sized to protect the bird and its habitat under the approved plan.
  • Relocate an animal only when authorised and when remaining at the work site presents a demonstrated risk, using nearby retained wetland habitat selected by the project ecologist and consistent with approval conditions.
  • Take an injured bird to an appropriately qualified veterinarian or authorised wildlife carer through the approved wildlife rescue pathway, and record the transfer.

During habitat disturbance: Habitat and wetland feature handling

  • Do not remove or damage nest platforms, dense nesting vegetation, feeding platforms, reedbeds, rushbeds or sedgelands until the fauna spotter catcher and project ecologist have confirmed that the area is clear and the work is authorised.
  • Do not alter water levels, block inflows, pump out wetlands or redirect runoff without controls that maintain suitable habitat and comply with the fauna management plan.
  • Keep felled vegetation, spoil and machinery out of water and retain vegetation that provides shallow-water foraging and dense nesting cover.
  • If wetland vegetation, water quality, hydrology or habitat differs materially from the approved assessment, stop the relevant work and reassess the impact before proceeding.
  • Use particular care around artificial wetlands and rice fields, which can provide habitat that is more reliable than some natural wetlands.

During habitat disturbance: Stop-work triggers and records

  • Stop work if an Australasian Bittern, nest, eggs, young, injured bird or previously unmapped suitable wetland habitat is found within or near the disturbance area.
  • Stop work after any breach of wetland exclusion fencing, unapproved vegetation removal, sediment release, pollution event, dewatering incident or change to wetland inflows.
  • Record the time, location, activity, machinery, people present, bird or nest details, photographs, weather, immediate controls, decisions, approvals and restart authority for every incident.
  • Restart only after the authorised project ecologist or other nominated decision-maker confirms that the controls and any revised approval conditions are in place.
  • Report significant incidents and confirmed records to the relevant regulator, approval authority and state wildlife database as required by the project approvals.

After habitat disturbance: Post-clearance checks

Post-clearance work must confirm that no bird, nest or suitable wetland habitat was missed and that the project has not reduced water supply or habitat quality. Retain controls until exposed areas are stable and rehabilitation is established.

  • Complete a fauna spotter catcher inspection of the cleared area, wetland edge, access route and retained habitat immediately after each work stage.
  • Repeat nocturnal listening and visual checks where suitable habitat remains, especially during October to February or after water levels change.
  • Inspect retained wetlands for injured birds, new nests, damaged reedbeds, altered water levels, sediment, pollution, salinity, acidification, grazing, trampling and fire damage.
  • Compare post-clearance photographs, mapped habitat and water conditions with the pre-clearance baseline and record all differences.

After habitat disturbance: Monitoring and compliance

  • Monitor retained and rehabilitated wetland habitat for Australasian Bittern presence, calling activity, nesting evidence, water depth, vegetation structure and threats identified in the approval or fauna management plan.
  • Continue monitoring through relevant breeding and non-breeding periods where the project affects a known wetland, drought refuge, rice field or wetland catchment.
  • Maintain exclusion fencing, sediment controls, spill controls and no-go markers until the supervising ecologist confirms that they are no longer needed.
  • Investigate any decline in habitat area or quality, loss of wetland water, reduced vegetation cover or new predator, weed, grazing or fire impacts, and implement corrective action.

After habitat disturbance: Close-out and offsets

  • Provide the regulator, approval authority and land manager with the final fauna records, incident register, maps, photographs, rehabilitation results and monitoring data required by the project approval.
  • Submit verified Australasian Bittern observations and significant breeding or habitat records to the relevant state wildlife database.
  • Complete any approved offset, compensatory habitat, environmental water, wetland restoration or management action and report measurable outcomes.
  • Do not treat an offset as a substitute for avoiding or minimising direct damage to occupied or suitable wetland habitat.

Rehabilitation actions: Restore wetland structure and water

Rehabilitation should restore wetland function and the dense vegetation structure used for feeding, nesting and concealment. The priority is to restore suitable water regimes, retain drought refuges and control threats over a period long enough to measure habitat recovery.

Reported preferred foraging water depth in WA: Less than 30 centimetres

Reported nesting vegetation: Baumea, Gahnia, Typha, sedges and Melaleuca-associated wetland vegetation

  • Reinstate natural or approved environmental water regimes that provide shallow foraging water and support dense emergent vegetation without permanently flooding or drying the wetland.
  • Restore wetland inflows and local catchment processes where construction has diverted, blocked or contaminated surface water or groundwater.
  • Plant or encourage locally appropriate native wetland vegetation, including reeds, rushes and sedges such as Baumea, Gahnia, Typha and Eleocharis where suited to the site and approved rehabilitation design.
  • Create or restore a mixture of shallow water with low to medium density vegetation for foraging and denser emergent vegetation for nesting.
  • Do not use Typha as the only rehabilitation plant where its expansion could produce dense stands that reduce habitat quality, and manage invasive or excessive Typha in accordance with site-specific ecological advice.

Rehabilitation actions: Control threats and protect habitat

Reported recovery time for some Baumea habitat after fire: More than 10 years

Predators identified in the WA recovery plan: Foxes, feral cats, rats and pigs, with native predators also recorded

  • Control foxes and feral cats around occupied and rehabilitated wetlands through an approved program that protects domestic animals and non-target wildlife.
  • Exclude or manage cattle, horses, deer, goats and pigs where grazing or trampling can damage nests, reduce cover or degrade foraging habitat.
  • Control weeds such as blackberry and Sydney golden wattle where they encroach into foraging habitat, and prevent construction weeds from entering the wetland.
  • Design and maintain fire management that prevents intense or frequent fire through nesting and reedbed habitat, while allowing site-specific ecological advice where vegetation becomes too dense.
  • Avoid prescribed burning when wetlands are dry and vulnerable to severe fire damage, because Baumea habitat may take more than 10 years to recover after fire.

Rehabilitation actions: Monitor rehabilitation success

WA recovery plan success measures: Australasian Bitterns remain extant at viable important wetland suites, and the area and quality of monitored habitat is maintained or increased

Important WA wetland suites include: Muir-Unicup, Lake Pleasant View and Mount Manypeaks wetlands, Cape le Grand wetlands, Benger Swamp and Vasse-Wonnerup

  • Set a pre-works baseline for wetland area, water depth, vegetation cover and structure, salinity or acidity where relevant, weed cover, grazing, fire damage and Australasian Bittern detections.
  • Monitor nocturnal calls, breeding activity, habitat occupancy and wetland condition during suitable calling seasons, using repeat locations and methods.
  • Measure whether the rehabilitated area maintains or increases suitable habitat and whether Australasian Bitterns remain present at the affected wetland or wetland suite.
  • Investigate failure if habitat area or quality declines, water regimes are not maintained, vegetation does not establish, or Australasian Bitterns do not return where return was an approved success objective.
  • Use monitoring results to adjust water management, revegetation, weed control, predator control and fire management rather than ending maintenance when planting is complete.

Sources