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Musk Duck (Biziura lobata)

The Musk Duck is a large, stiff-tailed Australian waterbird that uses deep freshwater wetlands, reed-fringed lagoons, river systems and some estuarine or coastal waters. It matters on development sites because it can be difficult to detect while diving, depends on permanent or seasonally flooded wetlands with dense cover, and may be affected by wetland drainage, hydrology changes, vegetation removal and disturbance during breeding.

Conservation status

Victoria, Flora and Fauna Guarantee Act 1988: Vulnerable.

Breeding season

Timing varies with rainfall and water availability, but breeding is generally concentrated from mid-winter through summer. Newly flooded wetlands may attract dispersing birds at other times of year, so presence should not be assumed to be limited to the breeding season.

Survey effort should account for diving behaviour and changing wetland use. A single shoreline or aerial observation may miss birds, particularly where dense cover is present.

  • Breeding: Male displays occur from about mid-July to early August. Breeding begins in July or August and continues through December or January.
  • Laying and incubation: Females nest in dense rushes, reeds or cutting grass. Incubation is about 24 to 26 days, and clutches may be laid as late as January.
  • Dependent young: Chicks are precocial but usually remain with the female for several months. The timing shown is a typical pattern based on the July or August to December or January breeding period.
  • Movement and dispersal: Local dispersal can occur when wetlands flood, and birds may colonise newly flooded ephemeral wetlands after inland rain. Musk Ducks also occur as non-breeding visitors at some wetlands, including Western Port.
  • Highest clearing risk: Clearing or disturbance is most likely to harm the species from July to January, when males display, females nest and dependent young may be present. Peak risk is expected from August to December because this overlaps laying, incubation and early dependent young.

Identification

Musk Ducks are heavy-bodied diving ducks with a distinctive stiff tail and a very low profile in the water. They are more often detected by careful observation on open water than by signs on land.

Males are almost blackish brown, with fine pale barring and speckling. Females are smaller but have broadly similar plumage. Both sexes have long, stiff tail feathers that may be held in a fan above the water.

An adult male has a large pendulous lobe below the bill. The lobe becomes more prominent during the breeding season, and adult males may produce a strong musk odour from a gland near the rump.

Male length: Up to about 92 cm

Female length: About 61 cm

Male weight: Up to about 3.6 kg

Female weight: As little as about 0.9 kg

Identification: Distinguishing features

The combination of a heavy body, very low swimming profile, long stiff tail and male bill lobe separates the species from most other Australian ducks. It may look like a small submarine when swimming and is often seen diving rather than flying.

The legs are positioned far back on the body. This assists swimming and diving but makes the bird clumsy on land, so it is usually found on water rather than walking along the shore.

Identification: Field signs and detection

Musk Ducks forage almost entirely by diving. A bird may disappear ahead of an approaching observer or aircraft and remain submerged, so absence from a rapid visual check does not demonstrate absence from suitable habitat.

Males produce conspicuous splashing displays, including paddling kicks, plonk kicks and whistle kicks. Calls include a whistle and a distinctive plonk sound. Breeding females nest in dense rushes or cutting grass, and nests may also be placed on partly submerged branches during flooding.

Reliable species-specific information on tracks, scats, sloughs and eyeshine was not identified in the supplied documents. Avoid flushing a bird from dense cover during the breeding season unless necessary.

  • Search deep open water, reed edges and sheltered wetland margins from a stationary vantage point.
  • Allow time for repeated scans because diving birds may be missed by a single observation.
  • Use binoculars or a telescope where possible, and record birds that dive before identification is complete.

Distribution: Range and subpopulations

Musk Ducks are endemic to Australia and occur mainly in the southern part of the continent. The supplied documents identify eastern and western populations separated by the Nullarbor Plain, with additional populations on Kangaroo Island and in Tasmania.

The species occurs in southern Australia, including coastal and inland wetlands. The eastern and western populations are genetically isolated by the Nullarbor Plain. Populations also occur on Kangaroo Island and in Tasmania, separated from mainland Australia by Bass Strait and Backstairs Passage.

The supplied documents do not provide a complete state by state range or a bioregion level distribution. They support use of the species profile across southern Australian wetland regions, including temperate freshwater systems and some estuarine waters.

Broad Australian range: Southern Australia

Recognised populations: Eastern and western populations, separated by the Nullarbor Plain

Additional populations: Kangaroo Island and Tasmania

Bioregion information: Specific bioregion boundaries are not provided in the supplied documents

Distribution: Known stronghold example and trend

Western Port Ramsar Site in Victoria has supported internationally significant numbers of Musk Ducks. The species is mainly recorded there as a non-breeding visitor and disperses to breed at more distant wetlands.

Counts can underestimate abundance because flocks on the sea are easily missed and the birds dive ahead of approaching observers. The available account states that the population appears to be decreasing, but does not provide a current national population estimate.

Western Port one per cent reference population: 250 birds

Western Port maximum count, 1973 to 1983: 264 birds

Western Port maximum count, 1984 to 2009: 226 birds

Western Port years exceeding the one per cent threshold: 1 of 35 full survey years

National population estimate: Not provided in the supplied documents

Reported trend: Appears to be decreasing, based on the cited account

Habitat: Wetland types

Musk Ducks are strongly associated with water and are poor walkers. They use deep, permanent or seasonally flooded wetlands with dense emergent vegetation, and may also use river systems, coastal waters and estuarine waterways.

Typical habitat includes deep freshwater lagoons, permanent swamps, marshes, lakes, river systems and temporary pools after substantial rainfall. The species may also forage in marine or estuarine habitats, including coastal waters and Western Port.

In spring, Musk Ducks move to locations with permanent water and substantial cover vegetation. Flooded lowlands and wetlands with stable water levels provide habitat for nesting and raising young.

Habitat: Vegetation and structure

Important structural features include dense rushes, reeds, cattails and cutting grass around open water. Dense emergent vegetation provides cover near feeding and nesting areas.

Wetlands with submerged or immersed vegetation are used for feeding. A partly submerged branch may support a nest during flooding or wet years.

  • Retain deep open-water areas connected to dense reed, rush or cutting-grass margins.
  • Protect wetland vegetation belts and shallow submerged vegetation from clearing, trampling and machinery access.
  • Maintain water levels and inflows that support permanent or seasonally flooded wetland habitat.

Habitat: Climate and elevation

The species is associated with temperate Australia. The supplied documents do not provide an elevation limit or a defined climatic boundary.

Musk Ducks can colonise ephemeral wetlands after inland rain and may disperse locally when new wetlands flood.

Foraging habitat: Diet

Musk Ducks feed mainly underwater in shallow to moderately deep areas where submerged or immersed vegetation is abundant. They obtain most food by diving and may use both freshwater and coastal or estuarine waters.

The diet consists mainly of aquatic animals, including freshwater yabbies, freshwater shrimp, snails, freshwater mussels and aquatic insects. Seeds from marsh and upland plants are also eaten.

Molluscs and aquatic insects make up important parts of the diet. Adult males have been reported to eat a greater proportion of molluscs than females or immature birds. Fish, frogs and small ducklings have also been reported as occasional food items.

Main feeding method: Diving

Main animal foods: Molluscs, aquatic insects and aquatic crustaceans

Other foods: Seeds, fish, frogs and occasionally small ducklings

Male diet example: Molluscs about 60 per cent and trichopterans about 36 per cent in the cited account

Foraging habitat: Foraging locations

Musk Ducks generally feed in shallower portions of wetlands where submerged or immersed vegetation is present, although they require sufficient water depth for diving. They may forage in deep freshwater lagoons, estuarine waterways and occasionally marine habitats.

The supplied documents do not provide a measured home range or foraging distance. Band recoveries indicate local dispersal and movement between wetlands, including colonisation of newly flooded areas.

  • Inspect open water, submerged vegetation beds and reed-fringed margins when assessing potential foraging habitat.
  • Do not rely on shoreline searches alone, because birds may be feeding underwater or offshore.
  • Consider recently flooded wetlands as potential feeding habitat, particularly after substantial inland rainfall.

Breeding habitat: Breeding biology

Musk Ducks breed on permanent or seasonally flooded wetlands with dense emergent vegetation. Males display on open water, while females select concealed nesting sites and provide all care for the young.

Breeding begins with male display on permanent water. Displays include splashing kicks, tail cocking, inflation of the bill lobe and whistles. The breeding season extends from July or August to December or January, with clutches recorded as late as January.

Females build the nest and provide incubation, protection and food for the young. Chicks are precocial, can swim and dive soon after hatching, and usually remain with the female for several months. Usually only one or two young survive from a clutch.

Breeding season: July or August to December or January

Breeding interval: Usually once per year

Usual clutch size: 2 to 3 eggs

Reported larger clutches: 5 to 6 eggs

Eggs: Large, elliptical and green

Incubation period: 24 to 26 days

Age at sexual maturity: 2 to 3 years

Lifespan: About 23 years in captivity; wild lifespan not established in the supplied documents

Breeding habitat: Nest habitat

Females nest in dense rushes, reeds or cutting grass near water. Nests in cutting-grass sites are made from dry stems and small amounts of down, and usually have a hood formed from folded grass stems.

During flooding, a nest may be built on a partly submerged tree branch using sticks and bark. Nesting activity declines when water levels retreat and flooded cutting grass becomes unavailable.

  • Retain dense emergent vegetation around permanent and seasonally flooded wetlands.
  • Avoid clearing or driving through reed beds, rushes and flooded cutting grass during July to January.
  • Maintain suitable water levels through the breeding season and avoid rapid drawdown where practicable.

Sheltering habitat: Cover and refuge

Musk Ducks shelter on water and within dense wetland vegetation rather than using terrestrial dens, hollows or burrows. Their diving behaviour is an important escape response to aerial predators and human approach.

Dense rushes, reeds, cattails and cutting grass provide cover for females, nests and dependent young. Open water close to dense cover allows adults and young to dive or move away from danger.

Musk Ducks may remain submerged when approached. This behaviour can reduce detection during surveys and can also expose birds to prolonged disturbance if observers, boats or machinery continue to approach.

  • Retain dense vegetation at the margins of deep water and around flooded lowlands.
  • Provide undisturbed water refuge beside construction exclusion zones.
  • Use distant observation points rather than approaching birds by boat or along the shoreline.

Sheltering habitat: Nests and other structures

Known nest sites include dense rushes, cutting grass and partly submerged branches. No species-specific den, burrow, hollow, roost or refuge dimensions are given in the supplied documents.

Nest material and structure may vary with site conditions. Cutting-grass nests use dry stems and down, while nests on partly submerged branches use sticks and bark.

Threats: Wetland loss and hydrology change

The strongest documented threats are loss of permanent wetland habitat, drainage or altered water levels, and drowning in fishing nets. Development activities can add direct risks by removing emergent vegetation, changing wetland hydrology and disturbing breeding birds.

Musk Ducks depend on permanent swamps and wetlands with suitable water levels. Drainage for agriculture is identified as a conservation concern, and nesting activity declines when water levels retreat.

On construction and infrastructure sites, wetland filling, dewatering, altered inflows, changed drainage lines and rapid drawdown can remove feeding, nesting and refuge habitat.

  • Map all deep water, emergent vegetation and recently flooded areas before works begin.
  • Keep spoil, sediment and machinery out of wetlands and their inflow paths.
  • Stage dewatering and water level changes outside the breeding period where practicable, and inspect retained habitat before each change.

Threats: Clearing, disturbance and fragmentation

Removal of reed beds, rushes, cattails or cutting grass can reduce cover, nesting sites and access to feeding water. Persistent disturbance may cause birds to dive, move away from suitable habitat or abandon an active nest.

The species mainly uses water and may be overlooked if surveys focus only on land or shoreline habitat. Fragmenting a wetland from nearby cover can reduce its value even where open water remains.

  • Establish exclusion zones around wetland margins and dense emergent vegetation before clearing.
  • Use a fauna spotter catcher or qualified ecologist to check open water, reed beds and partly submerged branches before works.
  • Stop work and reassess if a female is repeatedly entering dense vegetation, a nest is found, or adults show sustained alarm or diving responses.

Threats: Fishing nets, predators and other risks

Musk Ducks can become entangled in fishing nets and drown. Hawks and eagles are recognised predators, and the species responds by diving when aerial predators appear.

The supplied documents do not identify a species-specific disease, fire response or road mortality rate. General controls remain appropriate where roads, fire, predators or disease could affect wetland habitat or breeding birds.

  • Remove or modify unattended nets and other entangling material from occupied wetland habitat.
  • Keep temporary fencing, sediment controls and cables taut, visible and clear of water where possible.
  • Prevent polluted runoff, invasive species spread and uncontrolled fire from degrading wetland vegetation or water quality.

Survey methodology: 1. Targeted wetland searches

Survey Musk Ducks in and around permanent or seasonally persistent water, especially deep freshwater wetlands, lagoons, river systems and estuarine waters with dense rushes, reeds or cattails. They dive and can remain submerged ahead of approaching aircraft, so a single method or survey is unlikely to detect all birds.

Search all retained and potentially affected waterbodies, including deep freshwater lagoons, reed-fringed wetlands, river margins and estuarine waterways.

Search from the shoreline or other suitable observation points and scan open water, dense emergent vegetation and sheltered margins.

Use repeated observations where practicable because Musk Ducks may occur alone or in small groups outside the breeding season and may remain submerged when approached.

Preferred habitat: Deep-water wetlands, river systems and coastal waters, with substantial cover vegetation such as rushes and cattails.

Feeding habitat: Shallower areas with submerged or immersed vegetation, where birds dive for aquatic animals and plants.

  • Undertake searches when the water surface is visible and wind, glare and rain do not materially reduce detection.
  • Record the date, start and finish time, weather, waterbody, observer position, survey area, water depth where known, vegetation cover and all Musk Duck observations.
  • Treat a non-detection as inconclusive where dense reeds, rushes, cattails, glare or submerged birds limit visibility.

Survey methodology: 2. Breeding-season and nest-area searches

Give particular attention to dense rushes, cutting grass, reeds and partially submerged trees during the breeding period.

Breeding occurs from July or August through December or January. Females build nests in dense rushes and may also nest on partially submerged branches or trees.

Breeding period: July or August to December or January.

Clutch size: Usually 2 to 3 eggs, with reports of up to 5 to 6 eggs.

Incubation: 24 to 26 days.

  • Search likely nesting vegetation from a distance before entering or disturbing wetland margins.
  • Do not flush a suspected breeding bird unless absolutely necessary, and do not use flushing methods on breeding birds.
  • Record suspected nests, broods, displaying males, recently fledged young and the extent of dense nesting vegetation so these areas can be protected during works.

Survey methodology: 3. Aerial and remote detection

Use aerial survey only as a supplementary method for large or inaccessible wetlands. Musk Ducks can dive and remain submerged ahead of approaching aircraft, and aerial counts can underestimate waterbirds, particularly where dense cover is present.

Use remote observation or recording equipment where repeated observation is needed and access is limited, provided the equipment does not disturb birds.

Known detection issue: Musk Ducks may dive and remain submerged ahead of approaching aircraft.

Aerial count limitation: Counts may be underestimated by at least a factor of two in some waterbird surveys, especially in dense cover.

  • Do not rely on aerial detection alone to clear a wetland for disturbance.
  • Combine aerial or remote observations with targeted ground searches of shorelines, reed beds, rushes and sheltered water.
  • Record the survey platform, flight or observation path, visibility, detection constraints and any areas not adequately searched.

Survey methodology: Minimum effort and reporting

Western Port monitoring context: Historical counts recorded a maximum of 264 birds from 1973 to 1983 and 226 birds from 1984 to 2009, with the 1 per cent threshold exceeded in one of 35 full survey years.

  • Define the survey area before work starts and cover every waterbody, reed bed, rush bed and wetland margin that could be affected.
  • Use more than one observation occasion where habitat is difficult to view, the species has been recorded previously, or the first search is affected by diving birds, glare, dense cover or poor weather.
  • Document the method, dates, times, observers, conditions, effort, tracks or observation points, photographs, detection limitations and all negative results.
  • Record the maximum number of birds, behaviour, sex where confidently identified, habitat used and the location of each observation.
  • Submit confirmed records and significant survey results to the relevant state wildlife database and follow the data requirements of the relevant state or territory authority.
  • Retain field records, photographs, spatial files and fauna management records with the project environmental documentation.

Before habitat disturbance: Avoid and minimise

Plan works around the species' dependence on deep water, dense wetland vegetation and suitable breeding habitat. Musk Ducks are listed as Vulnerable in Victoria in the supplied project information, while the provided Western Port records show that the species can be missed during standard counts.

Habitat dependence: Musk Ducks depend on deep-water wetlands and use dense cover vegetation, including rushes and cattails.

  • Retain deep freshwater wetlands, permanent pools, reed beds, rushes, cattails, submerged vegetation and undisturbed wetland margins wherever practicable.
  • Avoid draining, infilling, isolating or reducing the depth of wetlands used by Musk Ducks.
  • Maintain connected waterbodies and movement routes between retained wetlands, river systems and estuarine waters.
  • Keep construction plant, spoil, sediment, fuel and runoff out of retained water and dense nesting vegetation.
  • Protect partially submerged trees and branches where they occur in or beside suitable breeding habitat.

Before habitat disturbance: Approvals and work planning

Victorian status: Vulnerable.

National status in supplied information: Not listed under the EPBC Act.

  • Check the current EPBC Act status before works commence and refer the action if another nationally listed matter or protected matter may be affected; the supplied species information states that Musk Duck is not EPBC listed.
  • Obtain any Victorian wildlife permits, threatened species approvals and local or project-specific authorisations required for a Vulnerable species.
  • Schedule vegetation removal, dewatering and noisy wetland works outside July or August to December or January where practicable.
  • Stage works so that suitable retained water and dense cover remain available before any occupied habitat is disturbed.
  • Prepare a fauna management plan that identifies survey methods, exclusion areas, stop-work triggers, authorised handlers, release sites, veterinary arrangements and reporting requirements.

Before habitat disturbance: Pre-clearance preparation

  • Complete a targeted pre-clearance search immediately before works, with extra attention to open water, reed beds, rushes, cattails, submerged vegetation and partially submerged branches.
  • Mark retained wetlands, nesting vegetation, buffers, access routes and no-go areas on plans and on the ground.
  • Use exclusion fencing where it can prevent machinery, people and dogs entering retained wetland habitat without blocking the birds' access to water.
  • Brief all operators and spotter catchers on the species' diving behaviour, habitat, handling limits and the requirement to stop work when a trigger is met.
  • Confirm a nearby retained release area with suitable water and cover before any capture or relocation is authorised.

During habitat disturbance: Daily controls and spotter coordination

Manage works as a controlled interaction between the fauna spotter catcher and machinery operators. The primary response is to stop disturbance, retain access to water and allow the bird to move away without pursuit.

Behaviour relevant to works: Musk Ducks dive readily and may remain submerged when approached.

  • Inspect the work area each day before machinery enters, including open water, wetland edges, reed beds, rushes and dense cover.
  • Keep the fauna spotter catcher in direct communication with operators and position machinery so the bird always has a clear route to retained water.
  • Use slow, staged clearing at wetland margins and stop plant before it reaches an occupied area or a bird's escape route.
  • Prevent sediment, contaminated water, concrete washout, fuel and rubbish from entering retained water.
  • Do not chase, corner, drive or repeatedly flush a Musk Duck.

During habitat disturbance: If a Musk Duck is found

  • Stop the activity that could harm the bird and establish a quiet exclusion area around the bird and its access to water.
  • Allow an apparently healthy bird to leave unaided towards nearby retained habitat whenever practicable.
  • Do not capture, transport or release the bird unless the person is authorised under the relevant permit and the approved fauna management plan.
  • If relocation is authorised, use the nearest suitable retained waterbody with dense cover and avoid releasing the bird into unsuitable dry ground or exposed water.
  • Place an injured or distressed bird in a secure, ventilated container only under authorised direction and arrange prompt assessment by a veterinarian or licensed wildlife carer.
  • Treat eggs, chicks and suspected nests as a stop-work matter and obtain advice from the relevant wildlife authority before proceeding.

During habitat disturbance: Habitat features and stop-work triggers

  • Stop work if a Musk Duck is found within the active work area, if a bird repeatedly dives near machinery, or if works would block access to retained water or dense cover.
  • Stop work if a nest, eggs, dependent young, displaying male or suspected brood area is identified.
  • Stop work if dewatering, sediment release, chemical contamination or unexpected wetland drawdown affects retained habitat.
  • Do not remove rushes, reeds, cattails, submerged vegetation or partially submerged nesting structures until the fauna spotter catcher and environmental officer confirm that the area is clear and the approved controls are in place.
  • Treat logs, rocks and burrows as general fauna habitat features if encountered, but prioritise protection of wetland water, dense emergent vegetation and submerged cover for this species.

During habitat disturbance: Records and escalation

  • Record every sighting, attempted observation, stop-work event, capture, relocation, injury, release and mortality on the same day.
  • Record the bird's location, habitat, behaviour, direction of movement, photographs where appropriate, people involved and machinery controls used.
  • Notify the project environmental officer and relevant wildlife authority of injured or dead birds, repeated displacement, nest disturbance, unauthorised handling or a failure of the approved controls.
  • Review the fauna management plan before work resumes after a stop-work event.

After habitat disturbance: Post-clearance checks

Confirm that clearing and construction have not removed access to suitable water or dense cover. Continue checks where works affect wetland depth, vegetation or water quality.

  • Inspect the cleared area and retained wetland margins for birds, nests, eggs, chicks, injured animals and trapped fauna before demobilising the fauna spotter catcher.
  • Check culverts, sediment controls, temporary dams, excavations and dewatered areas for birds that may have entered or become trapped.
  • Confirm that retained water remains accessible and that temporary fencing, ramps and exclusion controls have not blocked movement.
  • Remove temporary controls only after the environmental officer confirms that no further construction risk remains.

After habitat disturbance: Monitoring and reporting

  • Monitor retained wetlands during and after works for Musk Duck presence, breeding activity, water depth, vegetation cover, water quality and signs of disturbance.
  • Repeat targeted searches after major changes to water level, wetland vegetation or access conditions.
  • Compare post-work records with pre-work observations and investigate any decline in use, repeated displacement or loss of suitable cover.
  • Report incidents, survey results, mortalities, relocations and corrective actions to the relevant state wildlife database and approval agencies where required.

After habitat disturbance: Approvals and offsets

  • Complete all approval reporting and close-out requirements for state-listed fauna and any other protected matter affected by the project.
  • Determine whether an offset, compensatory habitat measure or additional management action is required under the relevant approval.
  • Do not use an offset as a substitute for avoiding or minimising direct disturbance to occupied wetland habitat.

Rehabilitation actions: Wetland and vegetation restoration

Rehabilitation should restore deep, persistent wetland water, dense emergent cover and shallow feeding areas. Musk Ducks feed mainly by diving for aquatic animals and plants, so wetland hydrology and water quality are as important as planting.

Food resources: Aquatic insects, crustaceans, snails, freshwater mussels, yabbies, fish, frogs and seeds.

Nest materials and sites: Dense rushes, cutting grass, and occasionally partially submerged branches or trees.

  • Restore wetland depth and seasonal water persistence to provide deep refuge and shallow feeding areas.
  • Replant or encourage locally appropriate rushes, reeds, cattails and other native emergent vegetation around suitable water margins.
  • Retain or reinstate submerged and immersed native vegetation used for feeding.
  • Reinstate partially submerged branches or trees only where they occur naturally and do not create hazards or obstruct safe water movement.
  • Prevent sediment, nutrients, toxicants, weeds and construction runoff from entering the rehabilitated wetland.

Rehabilitation actions: Habitat protection and maintenance

  • Control weeds that replace native rushes, reeds and submerged vegetation.
  • Maintain connected wetland habitat and avoid abrupt water-level changes during July or August to December or January where breeding may occur.
  • Manage domestic dogs, feral animals and other disturbance near wetland margins in accordance with the site management plan.
  • Retain natural logs, branches and other wetland cover where they provide refuge and do not obstruct access or create a safety risk.
  • Do not install nest boxes as a substitute for wetland rehabilitation because the supplied documents do not identify hollow trees or nest boxes as Musk Duck habitat requirements.

Rehabilitation actions: Fire, monitoring and success measures

Breeding period for monitoring: July or August to December or January.

Early breeding indicator: Displaying males, nests, eggs, broods or dependent young.

  • Manage fire so that dense wetland cover and nesting vegetation are not removed during the breeding period.
  • Inspect rehabilitated wetlands for water persistence, native emergent vegetation cover, submerged feeding habitat, weed invasion, erosion and water contamination.
  • Undertake repeat targeted searches during the breeding period and at other representative times to assess whether Musk Ducks return and whether breeding behaviour or young are recorded.
  • Use the pre-work habitat condition and bird records as the baseline for judging success.
  • Treat restoration as successful only when the approved targets for water availability, native wetland vegetation, water quality and fauna use are met and maintained for the required monitoring period.

Sources