Muir's Corella
Encyclopedia
Muir's Corella is a stocky, medium-sized white cockatoo
endemic to Western Australia
. It is the threatened nominate subspecies
of the Western Corella
.
with an erectile white crest. The undersides of the wings and tail are yellow. The feather
s between the eye and beak are deep salmon-pink, as are the bases of the feathers on the head and underparts. The eye is surrounded by a broad grey-blue eye-ring. The white feathers are often stained with soil because of the birds’ foraging
activities. The corellas have a wingspan of 90 cm, and range from 43–48 cm in length and 560–815 g in weight. They have a variety of loud and raucous calls. They are very similar in appearance to Butler's Corella
, the only other subspecies of the Western Corella, being slightly larger with a longer upper mandible.
and Avon Rivers
, south to Albany
and Augusta
, and eastwards to the Stirling
and Porongurup Ranges
. The birds were distributed in small, widely separated colonies throughout this range. However, the population has declined and the subspecies now only occurs in the Lake Muir
region where the remainder of the woodland habitat consists of fragmented remnants.
s and tubers which they dig up using the elongated upper mandibles of their bills. Cereal grains, including oats, barley and wheat, are eaten extensively in summer and autumn, while the corms of Onion Grass
are important in winter and spring.
s, including Jarrah and Marri
. Eggs are laid from September to November with a clutch size of 1-3. The incubation period lasts 26–29 days until fledging.
During the breeding season the birds feed close to the nest tree. After fledging, the young birds and their parents join other family groups to form large flocks that disperse to summer feeding areas. At the end of summer, breeding adults return to their nest sites while immature birds form nomadic flocks.
under Australia’s Environment Protection and Biodiversity Conservation Act 1999
. Population estimates vary; it may comprise up to 9000 individuals, including only about 2500 mature birds, having gradually recovered from a low of about 100 individuals in the 1940s after widespread shooting and poisoning in the late nineteenth and early twentieth centuries. Average life expectancy of adults has been estimated at 17 years for males and 14 years for females, with most young birds dying before they reach breeding age of 3–5 years old.
While current nest hollow and food availability are sufficient to sustain the population, changes in land use may threaten the corella where remnant vegetation and paddock trees are cleared to establish plantation
s of Blue Gum
and other species. It is potentially threatened by competition from, and interbreeding with, a species introduced from south-eastern Australia, the closely related Long-billed Corella
, which has nearby populations established from avicultural
escapes and releases. Other threats include illegal shooting and poisoning, as well as competition for nest hollows with feral
honey bee
s.
Because the corellas sometimes cause damage to crops, young trees, gardens, power lines and house fittings, the subspecies is a declared pest of agriculture. However, because it is listed as ‘rare or likely to become extinct’, it is illegal to destroy them, and damage mitigation measures must use non-lethal means.
Cockatoo
A cockatoo is any of the 21 species belonging to the bird family Cacatuidae. Along with the Psittacidae and the Strigopidae , they make up the parrot order Psittaciformes . Placement of the cockatoos as a separate family is fairly undisputed, although many aspects of the other living lineages of...
endemic to Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
. It is the threatened nominate subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Western Corella
Western Corella
The Western Corella formerly known as the Western Long-billed Corella, is a species of white cockatoo endemic to south-western Western Australia.-Taxonomy:...
.
Description
Muir's Corella has mainly white plumagePlumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
with an erectile white crest. The undersides of the wings and tail are yellow. The feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s between the eye and beak are deep salmon-pink, as are the bases of the feathers on the head and underparts. The eye is surrounded by a broad grey-blue eye-ring. The white feathers are often stained with soil because of the birds’ foraging
Foraging
- Definitions and significance of foraging behavior :Foraging is the act of searching for and exploiting food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce...
activities. The corellas have a wingspan of 90 cm, and range from 43–48 cm in length and 560–815 g in weight. They have a variety of loud and raucous calls. They are very similar in appearance to Butler's Corella
Butler's Corella
Butler's Corella is a medium-sized white cockatoo endemic to Western Australia. It is one of two subspecies of the Western Corella.-Description:...
, the only other subspecies of the Western Corella, being slightly larger with a longer upper mandible.
Distribution and habitat
Muir's Corella formerly inhabited woodlands and open country east of the main area of forest in south-western Western Australia, occurring north to the SwanSwan River (Western Australia)
The Swan River estuary flows through the city of Perth, in the south west of Western Australia. Its lower reaches are relatively wide and deep, with few constrictions, while the upper reaches are usually quite narrow and shallow....
and Avon Rivers
Avon River (Western Australia)
The Avon River is a river in Western Australia. It is a tributary of the Swan River totalling 280 kilometres in length, with a catchment area of 125,000 square kilometres.-Catchment area:...
, south to Albany
Albany, Western Australia
Albany is a port city in the Great Southern region of Western Australia, some 418 km SE of Perth, the state capital. As of 2009, Albany's population was estimated at 33,600, making it the 6th-largest city in the state....
and Augusta
Augusta, Western Australia
Augusta is a town on the south-west coast of Western Australia, where the Blackwood River emerges into Flinders Bay. It is the nearest town to Cape Leeuwin, on the farthest south-west corner of the Australian continent. In the 2001 census it had a population of 1,694; by 2006 the population of...
, and eastwards to the Stirling
Stirling Range
The Stirling Range or Koikyennuruff is a range of mountains and hills in the Great Southern region of Western Australia, 337 km south-east of Perth. It is located at approximately and is over 60 km wide from west to east, stretching from the highway between Mount Barker and Cranbrook...
and Porongurup Ranges
Porongurup National Park
Porongurup National Park is a national park in the Great Southern region of Western Australia , 360 km southeast of Perth and 40 km from Albany....
. The birds were distributed in small, widely separated colonies throughout this range. However, the population has declined and the subspecies now only occurs in the Lake Muir
Lake Muir
Lake Muir is a lake within an important wetlands area in the South West region of Western Australia, often known as the Lake Muir - Unicup System...
region where the remainder of the woodland habitat consists of fragmented remnants.
Behaviour
Muir’s Corellas are gregarious and may be seen in flocks of from ten to a thousand birds. They have traditional roosting sites, usually in dense timber, which they leave in the morning for their feeding areas and return to at night.Feeding
The corellas forage on the ground in large flocks and feed on a wide variety of seeds of both native and introduced plants, as well as cormCorm
A corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat ....
s and tubers which they dig up using the elongated upper mandibles of their bills. Cereal grains, including oats, barley and wheat, are eaten extensively in summer and autumn, while the corms of Onion Grass
Romulea rosea
Romulea rosea is a herbaceous perennial in the family Iridaceae. It is endemic to the western Cape Province in South Africa and is naturalised in Europe, Australia, New Zealand and California in the United States. Common names include Guildford Grass, Onion Grass and Rosy Sandcrocus.It is a small...
are important in winter and spring.
Breeding
The corellas nest in tree hollows of large, mature eucalyptEucalypt
Eucalypts are woody plants belonging to three closely related genera:Eucalyptus, Corymbia and Angophora.In 1995 new evidence, largely genetic, indicated that some prominent Eucalyptus species were actually more closely related to Angophora than to the other eucalypts; they were split off into the...
s, including Jarrah and Marri
Corymbia calophylla
Corymbia calophylla is a bloodwood native to Western Australia. Common names include Marri and Port Gregory Gum, and a long standing usage has been Red Gum due to the red gum effusions often found on trunks.It is distinctive among bloodwoods for its very large buds and fruit Corymbia calophylla...
. Eggs are laid from September to November with a clutch size of 1-3. The incubation period lasts 26–29 days until fledging.
During the breeding season the birds feed close to the nest tree. After fledging, the young birds and their parents join other family groups to form large flocks that disperse to summer feeding areas. At the end of summer, breeding adults return to their nest sites while immature birds form nomadic flocks.
Status and conservation
Muir's Corella is considered to be threatened because it consists of one relatively small and isolated population covering a fragmented range of about 3000 km2, with the actual area of occupancy being about 500 km2. It is listed as VulnerableVulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
under Australia’s Environment Protection and Biodiversity Conservation Act 1999
Environment Protection and Biodiversity Conservation Act 1999
The Environment Protection and Biodiversity Conservation Act 1999 is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and culturally significant places...
. Population estimates vary; it may comprise up to 9000 individuals, including only about 2500 mature birds, having gradually recovered from a low of about 100 individuals in the 1940s after widespread shooting and poisoning in the late nineteenth and early twentieth centuries. Average life expectancy of adults has been estimated at 17 years for males and 14 years for females, with most young birds dying before they reach breeding age of 3–5 years old.
While current nest hollow and food availability are sufficient to sustain the population, changes in land use may threaten the corella where remnant vegetation and paddock trees are cleared to establish plantation
Plantation
A plantation is a long artificially established forest, farm or estate, where crops are grown for sale, often in distant markets rather than for local on-site consumption...
s of Blue Gum
Eucalyptus globulus
The Tasmanian Blue Gum, Southern Blue Gum or Blue Gum, is an evergreen tree, one of the most widely cultivated trees native to Australia. They typically grow from 30 to 55 m tall. The tallest currently known specimen in Tasmania is 90.7 m tall...
and other species. It is potentially threatened by competition from, and interbreeding with, a species introduced from south-eastern Australia, the closely related Long-billed Corella
Long-billed Corella
The Long-billed Corella, Cacatua tenuirostris, is a cockatoo native to Australia, which is similar in appearance to the Little Corella and Sulphur-crested Cockatoo. This species is mostly white, with a reddish-pink face and forehead, and has a long pale beak, which is used to dig for roots and seeds...
, which has nearby populations established from avicultural
Aviculture
Aviculture is the practice of keeping and breeding birds and the culture that forms around it. Aviculture is generally focused on not only the raising and breeding of birds, but also on preserving avian habitat, and public awareness campaigns....
escapes and releases. Other threats include illegal shooting and poisoning, as well as competition for nest hollows with feral
Feral
A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...
honey bee
Honey bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
s.
Because the corellas sometimes cause damage to crops, young trees, gardens, power lines and house fittings, the subspecies is a declared pest of agriculture. However, because it is listed as ‘rare or likely to become extinct’, it is illegal to destroy them, and damage mitigation measures must use non-lethal means.