Introduction
The arrival of Europeans in Western Australia in 1827 was the beginning of rapid changes to the landscape. The area most affected was the major agricultural region in the southwest of the state, extending from the Murchison River, 400 kilometers north of Perth, inland to Norseman, and south to the coast at Esperance.5
Eight species of cockatoo occur in this region and have been impacted upon by environmental changes that followed European settlement and agriculture practices.
The short-billed or Carnaby’s white-tailed black cockatoo (Calyptorhynchus latirostris) are endemic to this area. Although population estimates are high, there is much concern for the long-term wellbeing of this species due to reduced breeding activities in many areas.
In 1995, collaborative conservation efforts between the Department of Conservation and Land Management, Perth Zoo, private aviculturists, landowners, and local shires began to halt the decline in suitable habitat and increase the breeding success of both captive and free ranging cockatoos.
Ecology and Breeding Biology
The Carnaby’s cockatoo migrates between the inland eucalypt woodland breeding grounds and the more coastal areas in the non-breeding season. The breeding season is July to December with one to two eggs laid in a deep nest hollow, 2 m above the ground. Very large old growth eucalypts of the species E. salmonophloia and E. wandoo are preferred. The chick fledges at 3 months of age and is fed for a further 4 months by the parents. After this, the birds form flocks and migrate to the coastal areas for the rest of the dry summer months, returning to woodlands after April or May, when the winter rains begin.
Around the Perth metropolitan area, the cockatoos move into pine plantations and stands of Pinus pinaster to feed on the cones and new twig growth.2
The main food item for the Carnaby’s cockatoo in the wheatbelt region are the seeds and flowers of native plants such as banksia, dryandra, grevillea, and hakea. Erodium, an introduced weed, is also fed upon during the limited time its seeds are available.3
Carnaby’s cockatoos become sexually mature at 4 years of age and may live up to 60 years. They form very strong pair bonds and return to the same area to breed year after year, and in some cases, use the same hollow.6
Threats to Survival
The enormous amount of land that has been cleared for agricultural use in the cockatoos’ range means that the native vegetation needed for food and nest sites is scarce and scattered. Breeding success of this species is dependent on these two resources.4
Carnaby’s cockatoos must compete with other deep hollow nesters such as galahs and corellas for nest sites. Galah numbers have increased with the introduction of European agrarian practices. Additionally, this species nest year-round and may already occupy favored sites when breeding season begins for the white-tailed black cockatoo.
Poaching of young chicks and eggs from nests not only has the immediate effect of decreasing the fledglings for the current breeding season but may impact further breeding success as nest hollows may be damaged or destroyed by the poachers. Although illegal, some white-tailed black cockatoos are still shot by farmers.
Some of the last remaining significant stands of native vegetation occurs along road verges and railway easements. Birds may be hit by cars when they are on the ground feeding near the roads. Many injured cockatoos are collected by CALM officers each year.
Conservation Efforts: Ex Situ
The Western Australian Department of Conservation and Land Management allows zoos, wildlife carers, and private aviculturists to hold white-tailed cockatoos classified as ‘derelicts’. This includes birds that are injured from gunshot and road accidents, and younger birds that are too imprinted for successful release to the wild. A licensing system is used to record these birds and they remain the property of the government. Since 1994, a program to confirm the species and sex of these birds, and pair them up for captive breeding has begun. People holding the birds are asked to voluntarily participate in the program which in some cases involved the relocation of the birds to another site. All birds are brought to Perth Zoo for an examination where the birds have a blood sample collected for DNA research, a microchip is placed, and surgical sexing is done, if the birds are immature.1 The goal of this program is to increase the number of provenanced black cockatoos in aviculture.
In 1996, CALM began another captive breeding program for the Carnaby’s cockatoo. This program involved taking 60 birds from the wild as eggs and chicks. These birds were divided among five private aviculturists for raising. The first year 56 birds were fledged. At 12 months of age, the birds had blood samples taken and were microchipped by zoo vets. CALM will receive 20% of the birds with the rest retained by aviculturists. CALM will sell its birds by public auction, with the money put into a trust to fund this and future captive breeding programs for other WA threatened bird species.
In 1997, 40 birds as chicks only were collected for this captive breeding program. As the goal of 100 captive provenanced Carnaby’s has been reached, no more collection from the wild is planned. There have been very few captive breedings of this species and until the birds sexually mature in 4 years and captive breeding occurs, the success of this program is unknown.
Other ex situ conservation efforts have focused on increasing public awareness of the plight of Carnaby’s cockatoos in the wild. A cockatoo information center has been created in the vicinity of Perth Zoo cockatoo aviaries.1 Also near the aviary, native plants and graphics have been used to highlight the important habitat contained in road verges.
Conservation Efforts: In Situ
Education staff at Perth Zoo have organized a joint venture involving Agriculture WA, CALM, primary schools, and farmers. Farmers near the town of Coorow, 250 kilometers north of Perth, were contacted and agreed to participate. Volunteers collected seeds from native plants on these farms identified as cockatoo food species. A Perth primary school accepted the job of extracting the seeds, then sowing the seeds collected, and caring for the seedlings in their school nursery. A primary school in the rural area was also contacted. Their role was to monitor where and on what the Carnaby’s were feeding, to monitor nests, and to monitor flight paths to identify remaining patches of native vegetation that the birds were using for food.1
Recently the Perth school has potted the native plants and the students will plant the seedlings at the farmer’s property and meet with their ‘sister’ school in the project.
CALM wildlife officers are also working to educate local governments responsible for road verges about the importance of this remaining native habitat for nesting sites. In some areas, the only remaining native gums of suitable size for nesting are next to roadways. This location makes the vegetation vulnerable to future roadwork and the nestlings easy prey for poachers. Only through education and recognition by the shire governments about the importance of these verge areas can they be preserved.
The conservation efforts aimed at Carnaby’s cockatoos have brought together a wide range of parties. The program can be used as a model not only for other cockatoo species, but also for other Australian native species whose numbers are declining for many of the same reasons. Co-operation and education are the key ingredients that can make any conservation effort a success.
Acknowledgments
The author wishes to thank the staff of CALM and Perth Zoo who have assisted with this project and this manuscript.
Literature Cited
1. Jupp, T. 1996. Carnaby’s Cockatoos—preventing a crisis. Psittascene 8:8–9.
2. Saunders, D.A. 1974. The occurrence of the white-tailed black cockatoo (Calyptorhynchus baudenii) in Pinus plantations in Western Australia. Aust. Wildl. Res. 1:45–54.
3. Saunders, D.A. 1980. Food and movements of the short-billed form of the white-tailed black cockatoo. Aust. Wildl. Res. 7:257–269.
4. Saunders, D.A. 1982. The breeding behaviour and biology of the short-billed form of the white-tailed black cockatoo Calyptorhynchus funereus. Ibis 124:422–455.
5. Saunders, D.A., I Rowley and G.T. Smith. 1985. The effects of clearing for agriculture on the distribution of cockatoos in the southwest of Western Australia. In: Birds of Eucalypt Forests and Woodlands: Ecology, Conservation and Management. Surrey Beatty, Sydney, Pp. 309–321.
6. Saunders, D.A. 1990. Problems of survival in an extensively cultivated landscape: the case of Carnaby’s Cockatoo Calyptorhynchus funereus latirostris. Biol. Conserv. 54:277–290.