Cabbage Tree Island
Encyclopedia
Cabbage Tree Island, also known as the John Gould Nature Reserve, is an uninhabited island with an area of 300,000 m2 lying 1.4 km off the mouth of Port Stephens
on the coast of New South Wales
, Australia
. It is named for the Cabbage-tree Palms
which are a feature of the island’s rainforest. It is the principal breeding site of the nominate subspecies
of the threatened Gould's Petrel
and, with the nearby Boondelbah Island
where there is also a small colony, has been classified by BirdLife International
as an Important Bird Area
. Both Cabbage Tree and Boondelbah Islands are gazetted nature reserve
s under the New South Wales National Parks and Wildlife Act, so protecting the island’s habitat from land uses incompatible with nature conservation. Access is only permitted for scientific and conservation purposes.
and Sandpaper Figs
, Native Plums, and Bird-lime Trees
.
which largely destroyed the understorey vegetation of the island and prevented its regeneration.
The removal of the sheltering understorey vegetation by rabbits led to increased exposure of the ground-nesting petrels and predation by Pied Currawong
s and Australian Raven
s. It also led to increased mortality following entanglement of the birds with the sticky fruits of the Bird-lime Trees which fell to the ground rather than being caught in the understorey. By 1992 there were fewer than 250 breeding pairs of Gould’s Petrel nesting on the Island, fewer than 20% of the pairs were producing fledglings
, fewer than 50 young were being produced each year, and adult mortality exceeded 50 birds each year.
Remedial management from 1992 onwards has included the eradication of rabbits on the island in 1997/98 and the removal of Bird-lime Trees from petrel nesting habitat, as well as the culling of currawongs and ravens. After a few pairs of Gould’s Petrels were discovered on Boondelbah Island in 1995, 1.5 km to the south, a translocation program was implemented to supplement the new breeding site with fledglings from Cabbage Tree. By 2004/05 it was estimated that the breeding colony on Cabbage Tree Island had increased to 2500 individuals comprising 1000 breeding pairs, that an average of 300 fledglings are produced annually, that 50% of pairs are producing fledged young, and average adult mortality is less than 10 birds a year.
Port Stephens
Port Stephens is a large natural harbour located about north-east of Sydney in New South Wales, Australia. It lies wholly within the Port Stephens Local Government Area although its northern shoreline forms the boundary between the Port Stephens and Great Lakes LGAs...
on the coast of New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. It is named for the Cabbage-tree Palms
Livistona australis
The Cabbage-tree Palm is in the Arecaceae family. It is a tall, slender palm growing up to about 25 m in height and 0.35 m diameter. It is crowned with dark, glossy green leaves on petioles 2 m long. It has leaves plaited like a fan; the cabbage of these is small but sweet...
which are a feature of the island’s rainforest. It is the principal breeding site of the 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 threatened Gould's Petrel
Gould's Petrel
Gould's Petrel is a species of seabird in the Procellariidae family. It is a small petrel, 30 cm long with a wingspan of about 70 cm. It is largely grey above and white below with a blackish crown and hindneck and a black M-shaped band across the wings and rump.The subspecies P. l...
and, with the nearby Boondelbah Island
Boondelbah Island
Boondelbah Island, also known as the Boondelbah Nature Reserve, is an uninhabited 14 ha island lying 2 km off the mouth of Port Stephens on the coast of New South Wales, Australia...
where there is also a small colony, has been classified by BirdLife International
BirdLife International
BirdLife International is a global Partnership of conservation organisations that strives to conserve birds, their habitats and global biodiversity, working with people towards sustainability in the use of natural resources...
as an Important Bird Area
Important Bird Area
An Important Bird Area is an area recognized as being globally important habitat for the conservation of bird populations. Currently there are about 10,000 IBAs worldwide. The program was developed and sites are identified by BirdLife International...
. Both Cabbage Tree and Boondelbah Islands are gazetted nature reserve
Nature reserve
A nature reserve is a protected area of importance for wildlife, flora, fauna or features of geological or other special interest, which is reserved and managed for conservation and to provide special opportunities for study or research...
s under the New South Wales National Parks and Wildlife Act, so protecting the island’s habitat from land uses incompatible with nature conservation. Access is only permitted for scientific and conservation purposes.
Description
Cabbage Tree Island is a small and rugged island, about 1.0 km in length, on a north-south alignment, by 480 m wide. It rises abruptly to a height of 123 m. The tree vegetation includes, as well as the Cabbage-tree Palms, DeciduousFicus superba var. henneana
Ficus superba var. henneana is a strangler fig only occurring in Australia. It is a variety of Ficus superba which occurs in China, Japan and parts of South East Asia....
and Sandpaper Figs
Ficus fraseri
Ficus fraseri, the White Sandpaper Fig or Shiny Sandpaper Fig, is one of several fig species commonly known as sandpaper figs. It is native to New South Wales and Queensland in Australia and New Caledonia...
, Native Plums, and Bird-lime Trees
Pisonia umbellifera
Pisonia umbellifera, commonly known as the Bird-lime Tree, is a species of plant in the Nyctaginaceae family. It grows throughout the tropical Indo-Pacific. It is native to the Andaman Islands, Indonesia, Malaysia, the Philippines, Thailand, Vietnam, China, Taiwan, Hawaii and Madagascar and the...
.
Gould’s Petrel conservation management
The petrels nest mainly in natural rock crevices among the rock scree of two gullies on the western side of the island, but also in hollow fallen palm trunks, beneath mats of fallen palm fronds and in cavities among fig tree buttresses. They breed in colonies with the nests often less than 1 m apart. Before significant active management of the island commenced, the breeding population was in decline. One major contributing factor was the presence of rabbitsEuropean Rabbit
The European Rabbit or Common Rabbit is a species of rabbit native to south west Europe and north west Africa . It has been widely introduced elsewhere often with devastating effects on local biodiversity...
which largely destroyed the understorey vegetation of the island and prevented its regeneration.
The removal of the sheltering understorey vegetation by rabbits led to increased exposure of the ground-nesting petrels and predation by Pied Currawong
Pied Currawong
The Pied Currawong is a medium-sized black passerine bird native to eastern Australia and Lord Howe Island. One of three currawong species in the genus Strepera, it is closely related to the butcherbirds and Australian Magpie of the family Artamidae. Six subspecies are recognised...
s and Australian Raven
Australian Raven
The Australian Raven is the largest Australian member of the genus Corvus and one of three Australian species commonly known as ravens. It is a more slender bird than the Common Raven of the Northern Hemisphere but is otherwise similar...
s. It also led to increased mortality following entanglement of the birds with the sticky fruits of the Bird-lime Trees which fell to the ground rather than being caught in the understorey. By 1992 there were fewer than 250 breeding pairs of Gould’s Petrel nesting on the Island, fewer than 20% of the pairs were producing fledglings
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
, fewer than 50 young were being produced each year, and adult mortality exceeded 50 birds each year.
Remedial management from 1992 onwards has included the eradication of rabbits on the island in 1997/98 and the removal of Bird-lime Trees from petrel nesting habitat, as well as the culling of currawongs and ravens. After a few pairs of Gould’s Petrels were discovered on Boondelbah Island in 1995, 1.5 km to the south, a translocation program was implemented to supplement the new breeding site with fledglings from Cabbage Tree. By 2004/05 it was estimated that the breeding colony on Cabbage Tree Island had increased to 2500 individuals comprising 1000 breeding pairs, that an average of 300 fledglings are produced annually, that 50% of pairs are producing fledged young, and average adult mortality is less than 10 birds a year.