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Great Egret (Ardea alba)

The Great Egret, Ardea alba, is a large white heron that feeds mainly in shallow freshwater and estuarine wetlands, but also uses damp grassland, fields, ponds and other watered areas. It is listed as a migratory species under the EPBC Act and is listed as Vulnerable in Victoria, so clearing near wetlands, nesting trees, roosts and regularly used feeding areas needs careful assessment.

Conservation status

Victoria, Flora and Fauna Guarantee Act 1988: Vulnerable.

Breeding season

Timing differs across Australia. Breeding is reported from October to December in the south and March to May in the north, while the species may be present in suitable Australian wetlands outside those periods.

Use local wetland observations and state records to refine timing. A single national calendar is not appropriate because breeding seasons differ between northern and southern Australia.

  • Breeding: Peak breeding is March to May in northern Australia and October to December in southern Australia.
  • Young: Young remain in the nest for about 40 days and fly at about six weeks. The timing follows local breeding, so dependent young may occur after the listed breeding months.
  • Movement and local dispersal: The species is listed as migratory under the EPBC Act material and NatureServe describes local movement, long-distance migration and post-breeding dispersal. The supplied documents do not give Australia-wide presence months or a single migration schedule.
  • Highest clearing risk: Risk is highest during regional breeding and dependent-young periods, March to May in northern Australia and October to December in southern Australia. Clearing or disturbance can also remove feeding and roost habitat at other times because the species may use wetlands throughout the year.

Identification

The Great Egret is a tall, long-legged white waterbird and the largest of the Australian egrets. It is usually encountered wading in shallow water or standing motionless at the edge of a wetland.

Adults have entirely white plumage, long dark legs and a long pointed bill. Outside the breeding season, the bill and facial skin are yellow, while the legs and feet are dark olive-grey to sooty black.

During the breeding season, the bill becomes mostly black, the facial skin becomes green, the upper legs become pinkish-yellow and long hair-like nuptial plumes hang from the lower back.

Young birds resemble adults but have a blackish bill tip.

Size: 70 to 90 cm in the Australian Museum account.

Weight: 935 g in the NatureServe account.

Identification: Separating it from similar egrets

Use the Great Egret's large body, long legs and long pointed bill to separate it from smaller Australian egrets. The Australian Museum identifies it as the largest of the Australian egrets.

The Little Egret is recorded as a separate species in the ecological assessment and is described as a small egret. Do not rely on bill colour alone during the breeding season, because Great Egret bill and facial colour change seasonally.

Identification: Field signs and behaviour

Great Egrets commonly forage alone, although they may occur in small flocks and may gather with other egrets. They roost in groups at night.

A breeding colony may contain large stick platforms in trees over water. Both sexes build the nest, incubate the eggs and care for the young, and nests may be reused from the previous year.

Expected site signs include white herons at shallow water, tracks or wading impressions in soft margins, feeding strikes in shallow water, and stick nests or grouped roosting birds in trees near water. The supplied documents do not describe a diagnostic call, scat, egg or feather field character.

Distribution: Australian range

The Great Egret occurs throughout most of the world and is common throughout Australia except the most arid areas. The supplied Australian documents do not provide a complete state by state range map or a reliable national population estimate.

In Australia, the species is expected across most coastal, inland and wetland regions where suitable water is available, with fewer records in the most arid areas.

The Swan Coastal Plain is documented as supporting Great Egrets through the migratory bird records for the Swan Coastal Plains Shrublands and Woodlands Conservation Management Zone.

The documents do not identify separate Australian subpopulations, named strongholds or a complete list of occupied bioregions. Local occurrence should therefore be checked against state databases, recent records and wetland surveys.

Distribution: Conservation status and records

The species is listed as a migratory species under the EPBC Act in the Swan Coastal Plains Conservation Management Zone material. The project assessment supplied for Essendon Airport recorded 64 Victorian Biodiversity Atlas records and assessed the site as having no suitable habitat.

The supplied listing identifies the species as Vulnerable in Victoria. The NatureServe account gives a global status of G5, or Secure, based mainly on its very large global range, while noting that suitable nesting habitat is relatively restricted.

Records in the Essendon Airport assessment: 64 Victorian Biodiversity Atlas records.

Global abundance in NatureServe: 100,000 to more than 1,000,000 individuals.

Global trend: No Australian population trend is provided. NatureServe describes the species as globally secure but says the global status needs review.

Habitat: Wetland and riparian habitat

Great Egrets use open shallow water and nearby wet ground, with trees or thickets near water needed for nesting colonies. They can move between wetlands, waterways, estuaries and non-wetland feeding areas.

Preferred habitat includes shallow, particularly flowing, water. Used habitats include marshes, swampy woodland, tidal estuaries, lagoons, mangroves, streams, lakes, ponds and damp grassland.

The broader habitat categories documented for the species include shallow lacustrine water, herbaceous, shrub and forested wetlands, riparian areas, low-gradient rivers, tidal flats, river mouths, lagoons and tidal rivers.

Fields and meadows may also be used, particularly where they provide wet ground or access to small prey.

Habitat: Features to retain on project sites

Before clearing, inspect shallow wetland margins, flowing channels, damp grassland, farm dams, ponds, riparian trees, swampy woodland and groups of roosting waterbirds.

Potential breeding habitat consists of tall trees over water or in woodland and thickets near water, especially where other colonial waterbirds are present.

The supplied documents do not give an Australian elevation limit, vegetation community list or minimum wetland size. Habitat assessment should therefore focus on water depth and permanence, prey access, wetland connectivity, nearby trees and evidence of repeated use.

Foraging habitat: Diet

Great Egrets usually feed alone in shallow water, where they wade slowly or stand still before stabbing at prey. They may also feed in fields, meadows and other wet ground.

Fish make up the bulk of the diet. Other recorded prey include frogs and other amphibians, aquatic insects, molluscs, snails, crustaceans, small reptiles, snakes, small mammals and other small animals.

The species is carnivorous, piscivorous and invertivorous. No particular Australian food plant is relevant to its diet.

Foraging habitat: Foraging method and area

The usual method is to wade through shallow water or stand motionless before striking at prey with the bill. Birds have also been recorded taking prey while flying.

Regular feeding areas may be separate from a breeding colony. The NatureServe account gives an inferred minimum extent of habitat use of 3 km when the actual extent is unknown, but notes that feeding areas can be several kilometres from colonies.

For construction surveys, inspect both the wetland itself and connected or nearby damp grassland, fields, meadows, drainage lines and shallow waterbodies.

Inferred minimum extent of habitat use: 3 km where the actual extent is unknown.

Breeding habitat: Breeding biology

Great Egrets breed colonially, often with cormorants, ibises and other egrets. Breeding habitat combines suitable nesting trees with nearby shallow water and other feeding areas.

Both sexes construct a large platform nest from sticks in a tree over water. Both sexes incubate the eggs and care for the young.

Colonies may be small or large, and nests may be reused from the previous year. A colony can therefore remain important even when active nests are not present during a single inspection.

The supplied documents do not provide an age at maturity or lifespan for the species.

Southern breeding season: October to December.

Northern breeding season: March to May.

Clutch size: Usually two or three in the Australian Museum account; two to six is also reported for Australia. NatureServe gives one to six, usually three to four in the north and two to three in the south.

Incubation: About 28 days in the Australian Museum account; 23 to 25 days in the NatureServe account.

Time in nest: About 40 days, with flight at about six weeks in the NatureServe account.

Age at maturity: Not provided in the supplied documents.

Lifespan: Not provided in the supplied documents.

Breeding habitat: Breeding site features

Retain tall trees over water and trees or thickets near water, particularly where stick nests, old nests or groups of colonial waterbirds are present.

Avoid assuming that a tree without a current nest is unimportant. Previous nests may be reused, and breeding colonies may be used repeatedly.

Maintain nearby shallow water and feeding habitat. The NatureServe account identifies nesting habitat as relatively restricted and records that water conditions were associated with nesting success in Florida.

  • Before clearing or pruning, inspect trees over and beside wetlands for current and old stick nests.
  • Treat a group of egrets, ibises or cormorants using trees near water as a potential breeding colony until its seasonal use is assessed.
  • Plan disturbance controls around both the nest trees and nearby feeding wetlands, because feeding areas may be separated from colonies by several kilometres.

Sheltering habitat: Night roosts

Great Egrets roost communally at night and nest in trees over water. The supplied documents provide no dimensions for roost trees, nest trees or preferred branch structure.

Great Egrets roost in groups at night and arrive at roosts around sunset or in darkness, departing at first light. Roosts may occur in trees or thickets near wetlands and other feeding areas.

Repeated evening use of a tree group is important evidence, even when no nests are present. Avoid removing or heavily disturbing trees used by a roost until the pattern of use is understood.

  • Check suitable trees near wetlands at dusk and again near dawn when daytime inspections do not explain local egret activity.
  • Record the number of birds, arrival and departure times, tree locations and whether the site is used by other colonial waterbirds.

Sheltering habitat: Nests and cover

Breeding nests are large stick platforms placed in trees over water. Nests may be reused from the previous year.

The species does not depend on mammal-style dens, burrows, tree hollows or leaf litter refuges. No species-specific ground cover, hollow diameter or nest height is given in the supplied documents.

Threats: Clearing and habitat loss

For development projects, the main documented sensitivities are loss of shallow wetland feeding habitat, loss of nesting trees and changes to water conditions. The supplied documents do not provide species-specific evidence for road mortality, fire, introduced predators or disease in Australia.

Clearing shallow wetlands, wetland margins, damp grassland, riparian vegetation, swampy woodland or trees over water can remove feeding, roosting or breeding habitat.

Nesting habitat is relatively restricted even though the species has a very large global range. Removing a nest tree, old nest tree or communal roost can affect use of the wider wetland.

The Essendon Airport assessment found no suitable habitat within the site and assessed the likelihood of occurrence as nil. This site-specific conclusion should not be applied to other projects without checking local habitat and records.

  • Avoid clearing trees over water and trees or thickets beside wetlands where nests, old nests or repeated roost use are present.
  • Map shallow water, wetland margins, connected drainage lines and regularly used feeding areas before finalising the clearing footprint.
  • Retain habitat links between roosts, colonies and feeding wetlands where practicable.

Threats: Fragmentation and disturbance

Breeding colonies and feeding areas may be separated by several kilometres, so a project can affect a colony indirectly by removing or disturbing its feeding habitat.

Regular human activity near a rookery may not always cause an obvious response. NatureServe records one study where weekly public viewing 229 m from a rookery caused no overt response, but this does not establish a universal disturbance distance for Australian colonies.

Distance reported in a disturbance study: 229 m from a rookery, with no overt response to weekly public viewing in that study.

  • Assess disturbance around both the colony and its associated feeding areas rather than assessing the nest trees alone.
  • Use site observations to set exclusion zones and timing controls because disturbance responses can vary with colony stage, access route and activity type.

Threats: Hydrology and water quality

Changes to water depth, flow, wetland inundation or water availability can reduce access to fish, frogs, crustaceans and aquatic invertebrates.

The NatureServe account reports that nesting success was associated with water conditions in Florida. The Australian documents do not specify thresholds for water depth, flow or water quality.

  • Prevent avoidable sediment, contaminants and altered drainage from entering wetlands used for feeding or nesting.
  • Maintain shallow-water margins and natural wetting patterns where they are part of the project area.

Threats: Roads, fire, predators and disease

The supplied documents do not identify a species-specific Australian road mortality rate, fire response, introduced predator impact or disease threat for Great Egrets.

Roads and construction activity can still remove or disturb wetland, roost and nesting habitat. These risks should be assessed from local records, observed bird movements and the proposed works rather than assumed to be absent.

  • Check whether access roads divide wetlands, roosts, colonies and feeding areas or require removal of riparian trees.
  • Inspect trees and wetlands after fire or burning proposals because loss of nesting trees, wetland cover or prey habitat may affect local use.
  • Record sick or injured birds and seek advice from the relevant wildlife authority or veterinarian; do not infer a disease event from an isolated observation.

Survey methodology: 1. Habitat and daytime searches

Great Egrets are large, conspicuous waterbirds, but detection depends on access to shallow water, wet grassland, roosts and breeding trees. Survey effort should focus on these features and on confirming whether the site supports regular foraging, roosting or breeding use.

Inspect all waterways, dams, wetlands, drainage lines, wet grassland, estuarine margins and wooded water edges within and adjoining the impact area.

Search shallow water and damp ground during daylight, when Great Egrets normally forage.

Record all sightings, numbers, behaviour, direction of flight, feeding areas, roosts and any birds carrying nesting material.

Search from a distance that does not flush birds, particularly where trees over water or groups of roosting birds are present.

Body length: 70 to 90 cm

Typical food: Fish, amphibians, aquatic insects, molluscs, crustaceans, small reptiles and other small animals

Survey methodology: 2. Wetland, roost and foraging checks

Inspect shallow, flowing water and other watered areas because these are preferred foraging habitats.

Check damp grasslands, ponds, lakes, streams, marshes, swamps, tidal estuaries, lagoons and mangroves where present.

Locate night roosts and assess whether birds use them regularly, noting trees, shrubs or other structures used for roosting.

Repeat observations where a single visit cannot distinguish a transient bird from regular site use.

  • Undertake checks across the range of wetland conditions present on the project site, including after water levels or flows change.
  • Record the number of birds, time of observation, habitat used and whether birds are feeding, roosting, commuting or displaying breeding behaviour.

Survey methodology: 3. Breeding colony checks

Inspect tall trees over or near water for stick nests and groups of Great Egrets or other colonial waterbirds.

Treat a suspected colony or rookery as a sensitive feature until an appropriately qualified ecologist has assessed it.

Schedule breeding checks in southern Australia during October to December, while recognising that breeding occurs from March to May in northern Australia.

Observe from outside the colony and avoid entering the wetland or approaching nesting trees unless access is necessary and authorised.

Breeding season in southern Australia: October to December

Breeding season in northern Australia: March to May

Nest location: A large stick platform in a tree over water

Usual brood information: Usually two or three young; clutch size 2 to 6 in the Australian Museum account

  • Look for adults carrying sticks, birds sitting on nests, eggs, chicks, repeated flights to the same trees and nest platforms being reused.
  • Map the colony, associated foraging areas, roosts and access routes separately.

Survey methodology: 4. Minimum effort and reporting

  • Use a qualified ecologist to set the final survey schedule when wetlands, roosts or possible breeding colonies may be affected, because the supplied documents do not provide an Australian survey-effort guideline for Great Egret.
  • Do not use spotlighting, trapping or handling as default methods for this species, because Great Egrets are best detected by daytime visual searches and habitat assessment and no trapping effort is specified in the supplied documents.
  • Complete additional visits when water conditions, seasonal use or an initial observation indicates that the site may provide regular habitat.
  • Submit confirmed records, including nil findings where required by the project, to the relevant state wildlife database, such as the Victorian Biodiversity Atlas in Victoria.
  • Report coordinates, date, time, number of birds, behaviour, habitat, breeding evidence, survey conditions, observer details and photographs where available.
  • Check current state and Commonwealth requirements before works, rather than relying only on the status information in a previous assessment.

Before habitat disturbance: Avoid and minimise

Before clearing or construction, establish whether the project could remove shallow-water foraging habitat, wetland edges, roost trees, breeding trees or access between these features. Great Egrets are mobile, but the loss or disturbance of a regularly used wetland or colony can affect site use.

  • Retain wetlands, waterways, shallow-water margins, damp grassland, riparian vegetation and trees over or beside water wherever practicable.
  • Retain known roost trees, nest trees, breeding colonies and the vegetation that screens them from machinery, vehicles and people.
  • Avoid filling, draining, diverting or increasing sediment in shallow water used for feeding.
  • Maintain movement between roosts, breeding trees and feeding areas, including safe flight access over retained habitat.
  • Keep project lighting, noise, dust and vehicle movement away from roosts and colonies where practicable.

Before habitat disturbance: Approvals and planning

Victorian listing in the supplied information: Vulnerable

EPBC information in the supplied information: Not listed, with Great Egret also identified as an EPBC Act migratory species in

  • Check the current EPBC Act status and whether the project may affect a listed migratory species or another protected matter, noting that the supplied project information identifies Great Egret as not nationally listed but includes it as an EPBC Act migratory species.
  • Check state wildlife, threatened species, animal welfare, vegetation removal and waterway approval requirements before disturbance.
  • In Victoria, treat the species as Vulnerable under the supplied status information and obtain advice on any required state permit or approval.
  • Prepare a fauna management plan that identifies wetland habitat, roosts, breeding trees, exclusion areas, stop-work triggers, authorised handlers and reporting requirements.
  • Stage works so that disturbance is kept away from southern breeding habitat from October to December and northern breeding habitat from March to May, unless a qualified ecologist has assessed the risk and the relevant authority accepts the approach.

Before habitat disturbance: Site preparation

  • Complete a pre-clearance inspection of all wetland, waterway, wet grassland, roost and potential breeding habitat immediately before works.
  • Mark retained wetlands, water edges, roosts, nest trees, exclusion zones and vehicle access routes on plans and on the ground.
  • Install exclusion fencing where it can prevent machinery and personnel entering retained wetland or roost habitat without obstructing bird movement.
  • Brief the fauna spotter catcher, supervisors and machinery operators on the species, mapped habitat, handling limits and stop-work triggers.
  • Confirm the location of a nearby retained wetland or other suitable habitat before any relocation decision is needed.

During habitat disturbance: Daily controls and supervision

Works should be controlled around wetland edges, roosts and any breeding colony. The fauna spotter catcher should have authority to pause work when a bird, nest, colony or unexpected habitat feature is at risk.

  • Inspect exclusion fencing, wetland buffers and marked habitat before machinery starts each day.
  • Use a fauna spotter catcher during clearing or other activities that may disturb retained habitat, roost trees or water edges.
  • Keep machinery, stockpiles, spoil, fuels and washdown water out of wetlands, waterways and shallow-water feeding areas.
  • Limit unnecessary vehicle movement, noise, dust, night lighting and personnel near roosts and colonies.
  • Stop or move work if birds repeatedly flush, cannot return to a roost or feeding area, or show persistent alarm near a breeding site.

During habitat disturbance: Spotter catcher and machinery interface

  • The fauna spotter catcher should inspect the work area before each clearing stage and maintain direct communication with the operator.
  • Proceed in small, controlled stages so the spotter catcher can inspect exposed ground, vegetation and water edges before machinery advances.
  • Keep machinery stationary while the spotter catcher checks a suspected nest, roost, injured bird or newly exposed habitat feature.
  • Do not allow machinery to enter a marked exclusion zone until the spotter catcher and environmental officer have cleared the area.
  • Use a qualified and authorised person for any capture, restraint or relocation, and do not direct untrained workers to handle a Great Egret.

During habitat disturbance: If a Great Egret is found

  • Pause work if the bird is within the work area, trapped, injured, unable to fly or being repeatedly disturbed.
  • Allow an able-bodied bird to leave without chasing it, and keep people and machinery back until it has moved to a safe location.
  • Do not catch, restrain, feed or transport the bird unless the handler is authorised, trained and acting under the project fauna management plan and applicable law.
  • If relocation is necessary, use nearby retained habitat that provides shallow water or another suitable wetland feature and minimise handling time.
  • Take an injured or sick bird to an appropriate veterinarian or licensed wildlife carer through the approved wildlife rescue pathway.
  • Protect any nest, eggs or dependent young in place and obtain advice from the project ecologist and relevant authority before resuming work.

During habitat disturbance: Stop-work triggers and records

  • Stop work for an active nest, dependent young, a breeding colony, a trapped or injured bird, or damage to a mapped wetland, roost or nest tree.
  • Stop work when sediment, fuel, concrete washout or other pollutants enter or threaten shallow water used by the species.
  • Record every sighting, incident, nest, colony, roost, exclusion-zone breach, handling event, relocation, injury and release outcome.
  • Record the date, time, location, number of birds, behaviour, habitat, works occurring, controls applied, personnel involved and photographs where appropriate.
  • Report incidents promptly to the environmental officer, project ecologist and any authority or wildlife carer specified in the fauna management plan.

After habitat disturbance: Post-clearance checks

After clearing or construction, confirm that no birds, nests or dependent young remain at risk and that retained wetland and roost habitat is functioning as planned. Continue controls where birds use the site during later project stages.

  • Inspect the cleared area, wetland margins, retained trees and exclusion zones at the end of each clearing stage and before demobilisation.
  • Check for injured or trapped birds, damaged nests, fallen nest trees, blocked drainage, sediment deposits and contaminated water.
  • Confirm that all temporary fencing, access controls and machinery exclusion measures remain effective around retained habitat.
  • Remove waste and temporary materials without entering or damaging retained wetland, roost or breeding habitat.

After habitat disturbance: Monitoring and reporting

  • Monitor retained wetlands, roosts and known foraging areas when the assessment or fauna management plan identifies ongoing risk.
  • Use repeat daytime observations to record whether Great Egrets continue to feed, roost or breed in retained habitat.
  • Investigate declining use, repeated flushing, water quality changes or loss of access between feeding and roosting areas.
  • Provide the final fauna report to the project environmental officer and relevant regulators, including survey results, incidents, mitigation actions and unresolved risks.
  • Submit required observations and incident records to the relevant state wildlife database and retain the project data in the environmental record.

After habitat disturbance: Offsets and residual impacts

  • Assess whether clearing has caused a residual impact on wetland, roost or breeding habitat after avoidance and mitigation measures are applied.
  • Apply any required Commonwealth or state offset, compensation or habitat protection measure in accordance with the relevant approval.
  • Do not treat an offset as a substitute for retaining an active breeding colony, nest tree, roost or regularly used wetland where those features can be avoided.

Rehabilitation actions: Wetland and water-edge restoration

Rehabilitation should restore the shallow-water, wetland-edge and wooded-water features used for feeding, roosting and breeding. Design the outcome around the habitat retained at the site and the hydrology needed to keep suitable shallow water available.

  • Re-establish shallow, flowing or otherwise suitable water and damp ground where these features were temporarily disturbed.
  • Reconnect retained waterways, wetlands, wet grassland and riparian vegetation where construction has interrupted access or drainage.
  • Stabilise exposed soil and control sediment so that runoff does not degrade feeding water.
  • Use locally appropriate native wetland, riparian and aquatic plant species selected for the project site, rather than planting a fixed species list that is not supported by the supplied documents.
  • Keep open shallow-water feeding areas available while retaining vegetated margins and trees near water.

Rehabilitation actions: Roost and breeding habitat

  • Retain mature trees over or near water wherever safe and practicable because Great Egrets place large stick nests in trees over water and roost in groups.
  • Where an approved rehabilitation design identifies a lost nesting feature, seek advice from the project ecologist on suitable replacement trees or nest platforms before installing any artificial structure.
  • Do not install nest boxes as a default measure, because the supplied documents describe stick nests in trees rather than nest-box use by Great Egrets.
  • Retain or restore sheltered roosting vegetation near feeding habitat and prevent routine access beneath known roosts.

Rehabilitation actions: Threat and site management

  • Control weeds that reduce wetland structure, block shallow-water feeding areas or prevent regeneration of native trees near water.
  • Prevent domestic animals, vehicles and unauthorised people from entering known roosts, colonies and wetland margins.
  • Manage erosion, altered water levels, drainage, dust, lighting and pollution so that restored habitat remains suitable for foraging.
  • Apply fire management in accordance with the site fire plan, protecting wetland-edge vegetation, mature nesting trees and roost habitat from inappropriate fire intensity or timing.

Rehabilitation actions: Monitoring and success measures

  • Inspect rehabilitated wetlands and water edges after construction and during the first wet and dry periods identified in the rehabilitation plan.
  • Measure survival and cover of planted vegetation, stability of water edges, water quality, persistence of shallow water and protection of retained trees.
  • Record Great Egret presence, number, feeding, roosting and breeding behaviour during repeat daytime observations.
  • Treat continued use of restored shallow water, wetland margins or roost habitat as a species-specific outcome, while recognising that absence on a single visit does not demonstrate failure.
  • Repair erosion, fencing, drainage or planting failures and continue monitoring until the approved rehabilitation criteria are met.

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