A striking feature of White Lagoon is the lunette formation. The lunettes are composed of calcareous, silty clay and are particularly steep. Lines of them form an arc around the eastern margin of White Lagoon and curve around the southern and northern ends.
There are many lunette formations on Kangaroo Island including the hummocks at Stranraer in the Hundred of MacGillivray, where lunettes fringe the eastern shore of White lagoon. These lunettes are 23 metres in height and usually occur on the eastern shores of lakes, lagoons and depressions, which intermittently contain water. The composition of these lunettes ranges from silt to clay. These sediments are usually structureless and poorly consolidated. The soils at times represent soil that is high in sodium with very little structure and poor drainage. Most of these lunette formations are grassed and rarely will trees be found on them. The lunettes at Stranraer do not have any trees on them, however between them and White Lagoon there are trees populations. Most lunette formations in Australia are encountered in the semi-arid regions of the southern states. Most lunettes appear to be fossil features rather than forming today.
The outermost generation of lunettes is very hummocky, so much so that the area has always been referred to as ‘The Hummocks.’ The leeward side of the lunettes appear to be steeper than the western facing slope.
Various theories have been presented as to how the hummocks were formed. One involves the trapping of westerly borne dust, particularly on the eastern shores of the lakes, by moist air above the lake.
A second theory involves the deflation of material from the dry lake floor by westerly winds and the deposition of this material on the eastern side of the lake, where it is trapped by vegetation. Thus any material capable of being transported by the wind can be incorporated into the lunette. Waves generated by winter westerlies have been important in accumulating material on the eastern shoreline and in fact, steepening the side of the lunette fronting White Lagoon.
The third theory is that these are remnants of a much larger ancestral lagoon, which was originally a water filled depression left on a coastal plain as the sea level retreated. The development of distinct and separate lunette lines around the lagoon, is evidence that the ancestral lagoon both contracted in size and migrated westward.
Between the outer hummocks area and the farm building of Stranraer, the terrain is occupied by a former lake floor and an older, much modified sequence of lunette ridges now mantled by resistant calcareous material known as calcrete. A grey black soil developed on the calcrete. This soil is soil that supports most of the Stranraer cropping and lucerne production, ideal for cropping with an alkaline soil pH. Farm buildings at Stranraer have been constructed out of stones that are a product of this soil/regolith process and have led to the dissolution and recementation of materials that were originally soft calcareous marls to form tough resistant building materials over perhaps many tens of thousands of years.
The White Lagoon Wetland System supports eight species of waterbirds listed on the international migratory bird treaties. Seven are listed on the Japan-Australia Migratory Bird Agreement (JAMBA) and seven are listed on the China-Australia Migratory Bird Agreement (CAMBA). These treaties, signed by the Australian government, oblige us to conserve the birds listed to enhance their survival worldwide.
The northern area of the Rush Lagoon wetland, which is not part of Stranraer is home to a sand quarry. This is very high quality sand that was used to lay the foundations for the Kingscote District Hospital that was completed in 1930 at the time of the great depression. In 1953, the Kingscote Council purchased the sand pit as it would then be used in the construction of buildings in Kingscote as it developed. In 1955 the town hall redevelopment was completed using sand from the MacGillivray quarry.
The southern area of the White Lagoon system is also home to a very high quality sand.. The clay lunettes in the above picture represent the hummocks and also the transition of salt water via the ground water system to D’Estrees Bay. These lunettes lie WNW-ESE. The most effective dune-forming modern winds during the dry (summer) season are likely to have been effective in lunette building (Campbell 1968). Therefore, the wind pattern between 7000 and 4000 years ago seems to be the same as the present, indicating no major shift during the past 7000 years. Wind velocities during this period must have been moderately high, to not only build the lunette, but also to raise waves producing the longshore drift necessary to maintain a supply of sand at the northern end of the lake 4000-7000 years ago the White Lagoon System operated as one system but today the system exists as two bodies of water, White Lagoon and Rush Lagoon. The site today exists of dune fields and shallow depressions relating to this and other former lakes. It is flattish and low lying, covered with mallee shrub land in which Eucalyptus cneorifolia or Kangaroo Island Mallee is the dominant vegetation. The sand quarry at the northern end of Rush Lagoon was extensively developed to assist the building development on Kangaroo Island. Most of the building construction in Kingscote was completed with the use of the MacGillivray quarry sand.
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Rush Lagoon - named due to the number of rushes present in the early days.
White Lagoon - named due to the salt layer ‘white crust’ on the surface
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Rush Lagoon was able to support cropping prior to 1956, now with the movement of the 1956 water mass, salt was exposed at the surface resulting in the soil becoming salty and unfit for agricultural purposes. The fencing of Rush Lagoon has resulted in the regeneration of the 1000s of melaleuca halmaturorum, also known as swamp paperbark. This also assisted with salinity management and protection for the migratory birds that flock to Rush Lagoon on an annual basis, whilst also protecting the water supply.
Rush Lagoon is 141.4 ha (350 acres) in size. During wet years the whole area becomes covered with water and migratory birds begin to move to the area in October in any given year.
Since 1984 the management of Rush Lagoon has been a very important part of the property. An extensive fencing program was put into place with the assistance of the Kangaroo Island Natural Resources group. The aim of the fencing program was to remove stock access to the area to encourage the natural regeneration of melaleuca halmaturorum.
This process of regeneration for Rush Lagoon has been a work in progress. If we look at the site now in 2012, the regeneration of the area is quite evident. The preservation of the natural resource base to encourage and protect the migratory bird population along with kangaroos and wallabies has been quite evident.
Salinity management has also been assisted with the regeneration of the area.
Wheat growing on the southern edge of Rush Lagoon in the early 1950s. However, with the flood water in 1956, White Lagoon water joined Rush Lagoon and the result was saline water entering the region which halted the growth of grass and other plant species.
The preservation of the Rush Lagoon environment has assisted in maintaining the water quality for the property.
An area at the northern end of the property was cleared of its bottlebrush in the 1960s to increase the grazing area for livestock. This area has never recovered and water lies there most of the year with no pasture growth for livestock. This area is a visual reminder of the impact of clearing especially in low lying areas and the value of vegetation. The area was cleared with crawlers and chains over a period of time.
The photo above shows the regeneration of the Melaleuca halmaturorum population on the eastern edge of Rush Lagoon after it was fenced off from livestock and is a haven for migratory birds from August until February.
This Malaleuca halmaturorum regeneration has occurred since 2010 on Rush Lagoon due to the extensive fencing plan to protect the area. This species is found in areas of Western Australia, South Australia’s Eyre Peninsula and south east of South Australia along the Coorong. This species can grow to 8 metres in height. It often forms thickets in swampy areas subject to waterlogging, including the fringes of salt lakes and coastal sand dunes. Some areas of Rush Lagoon are d
ifficult to walk through due to the density of the melaleuca halmaturorum. Mature seed capsules are maintained on plants for several seasons. With the fencing off of Rush Lagoon the germination will increase rapidly due to the longevity and viability of the seed.
Lee Lagoon is part of the Wattle Grove area, comprising 22.3 ha. This area was preserved in 1998 to reduce the impact of grazing livestock and to protect the area, which has numerous bottlebrush species that flower in October-November.
CHAPTER 8 - Migratory Birds of Kangaroo Island
Kangaroo Island is reknown for it’s migratory bird populations. The White Lagoon wetland system supports a number of these migratory birds as well as permanent bird populations. The following includes a description of the birds that can be found on White and Rush Lagoons.
Hoary-Headed Grebe-Poliocepalus poliocepalus
The Hoary-headed Grebe is found in all states and territories of Australia as well as in New Zealand. It is generally absent from the central arid regions of Australia.
The Hoary-headed Grebe is usually found away from the shoreline in large open waters, which may be estuarine, brackish or freshwater.
Little Pied Cormorant- Phalacrocorax melanoleucos
Almost any body of water in Australia, large or small, marine or fresh is likely to be frequented by the Little Pied Cormorant.
The Pied Cormorant is a large black and white bird with a long, grey, hooked bill and black legs and feet.
The Pied Cormorant is found throughout mainland Australia. It is more common in the south and along the coast of south-western Australia and is not found in the driest parts of the interior. It is also found in New Zealand.
Rush Lagoon is frequented by the Little Pied Cormorant due to the yabbies present as this forms part of their diet.
Australasian Shoveler-Anas rhynchotis
The Australasian Shoveler is a low-floating, dark headed duck, with a low sloping forehead blending to a heavy, square-cut, shovel-tipped bill.
The Australasian Shoveler is found in all kinds of wetlands, preferring large undisturbed heavily vegetated freshwater swamps. It is also found on open waters and occasionally along the coast.
In Australia these ducks are dispersive, but little is known about their movements. In New Zealand they are highly mobile.
The Australasian Shoveler is a filter feeder, using special lamellae (grooves) along the edges of the bill to filter insects, crustaceans and a variety of plants from the water.
Chestnut Teal-Anas castanea
The Chestnut Teal is found in south-western and south-eastern Australia. In the east, it is found from Rockhampton, Queensland to Ceduna, South Australia, being most common in New South Wales, Victoria and Tasmania.
The Chestnut Teal is found on wetlands and estuaries in coastal regions, and is one of the few ducks able to tolerate high salinity waters, although it still needs fresh water for drinking. It will also use open freshwater lakes, reservoirs and sewage ponds during dry seasons. Some movement occurs between breeding and non-breeding areas, but many birds do not move far.
The Chestnut Teal is often found in paddocks on Straraer grazing for insects, especially in the spring period when insects are at their highest with the warmer weather. This particular species can be seen on the edge of Rush Lagoon filtering the water surface or stripping seeds from plants.
Grey Teal- Anas Gracilis
Grey Teals are common in all sheltered watered areas. These include fresh, brackish and salt water and the birds can be found on the smallest area of water in the driest of areas. The most favoured habitat type is timbered pools and river systems of the inland areas, where these birds can be found in quite large numbers. The Grey Teal is grey to brown in colour and can be found on both Rush and White Lagoons, so are suited to both fresh and salt water systems. Their breeding can take place at any time of the year, the rate of population turnover is high with some birds living to eight years, however most on average live for 20 months.
During periods of drought, Grey Teal are very mobile in search of water, often travelling great distances.
Pacific Black Duck-Anas superciliosa
The Pacific Black Duck is mostly mid-brown in colour, with each feather edged buff. The head pattern is characteristic, with a dark brown line through the eye, bordered with cream above and below and a dark brown crown. The Pacific Black Duck is found in all but the most arid regions of Australia. Outside Australia, its range extends throughout the Pacific region.
Every coastal stream and lagoon in Australia has its fair share of the Pacific Black Duck. They are probably more widely distributed in Australia as a breeding species than any other.
The Pacific Black Duck is a surface-feeding duck taking both plants and animal food from the water. Rush Lagoon is an ideal environment for the Pacific Black Duck. Although these ducks are randomly nomadic, following floods and evacuating drought stricken areas, they are nonetheless permanent on some waterways around Australia.
The higher concentration of the Pacific Black Ducks on Rush Lagoon occurs in winter-spring, when he water levels are at their highest and aquatic plants are mature for feeding. It is at this time that most of the breeding occurs.
Pink Eared Duck-Malacorhynchus membranaceus
The Pink Eared ducks are common in most waterways of inland Australia. These ducks are nomadic and able to breed at any time.
The Pink Eared Duck is not mistakeable for any other duck.
This duck is found throughout Australia but only occasionally in Tasmania.
The Pink Eared Duck is found in timbered areas near water. It prefers shallow, temporary waters however, open wetlands support large flocks. It is a highly dispersive and nomadic species. This particular species of duck is able to survive in brackish and freshwater lakes, however most commonly seen on the edge of lakes feeding on insects, water fleas and freshwater algae.
Pink Eared Ducks are birds of the inland swamps and will fly great distances in search of water. Huge flocks often reach the coast in dry years.
Pink Eared Ducks feed in shallow warmish waters. The highly specialised bill is fringed with fine lamellae (grooves) to filter out the microscopic plants and animals which make up the bulk of its diet.
Freckled Duck-Stictonetta naevosa
The Freckled Duck is a dark greyish-brown duck with a large head that is peaked at the rear and has a distinctive narrow and slightly upturned bill. This species is considered one of the rarest water ducks in the world.
The Freckled Duck is found primarily in the south east and south west of Australia. The Freckled Duck prefers permanent fresh water swamps and creeks with heavy growth of cumbungi (bullrushes), lignum or tea tree. The melaleuca halmaturorum (tea tree) is an ideal habitat for the Freckled Duck and the conservation of Rush Lagoon has increased this species of tree. During drier times, the Freckled Duck moves from ephemeral (not permanent) breeding swamps to more permanent waters such as lakes, reservoirs, farm dams and sewerage ponds.
Freckled Ducks feed at dawn and dusk and at night on algae, seeds and vegetative parts of aquatic grasses and sedges and small invertebrates.
Australian Shelduck-Tadorna tadornoides
The Australian Shelduck is a large, brightly coloured duck with a small head and bill and lives in lowland areas such as large brackish lakes of the coats, which are their preferred habitat. They also congregate in deep freshwater lakes, large lagoons like Rush Lagoon and billabongs.
Australian Shelducks are usually unmistakable, with the upright stance and dark head contrasting with the white neck ring.
The Australian Shelduck prefers fresh waters and if in a saltwater habitat, needs to be within easy reach of fresh water. The majority of Australian Shelduck are seen on Rush Lagoon, as opposed to White Lagoon due to varying water quality and they are often seen in pairs.
The Australian Shelduck grazes on green grass on land or in shallow water. It also eats algae, insects and molluscs.
The clearing and conversion of some areas to
cropland and pasture has led to an increase in some local populations of the Australian Shelduck. Breeding territories are often established around farm dams.
Australian Shelducks grazing in Quail paddock, Stranraer, 2013. They feed on plants in shallow water or on land.
Musk Duck-Biziura lobata
The male Musk Duck is the largest of Australia’s ducks and has a powerful build.
Musk Ducks tend to be found in deep freshwater lagoons, with dense reed beds. They are normally seen singly or in pairs, but may form medium to large groups in the winter. Flight usually takes place at night.
Despite their bulky appearance, Musk Ducks are excellent divers and search underwater for the majority of their food. They mainly feed on animals, including aquatic insects, crustaceans, snails, shellfish, fish, frogs and ducklings, but some seeds of aquatic plants are also eaten on occasion.
Blue-billed Duck-Oxyura australis
The Blue-billed Duck is endemic to Australia, being found in the temperate wetlands of the southeast and south-west parts of the continent.
The Blue-billed Duck is almost wholly aquatic, and is seldom seen on land. Non-breeding flocks, often with several hundred individuals, congregate on large, deep open freshwater dams and lakes in autumn. The Blue-billed Duck feeds almost entirely by diving. It takes aquatic insects including chironomid fly larvae, caddis flies, dragonflies, flies and water beetle larvae. They may also eat the seeds, buds, stems, leaves and fruit of a wide variety of plants. Feeding occurs in permanent areas of clear fresh water
Kangaroo Island Page 10