Denis Saunders

Before European settlement, the Western Red-tailed Cockatoo Calyptorhynchus escondidus had a distribution confined to the Pilbara, Murchison, and Gascoyne regions of Western Australia. Since then, the species has expanded its range into parts of the northern and central wheatbelt of Western Australia. This paper describes a further expansion of the species’ range into a near-coastal, central wheatbelt area, and the first known breeding record in this area, representing a 72-km expansion of the known breeding range. Possible reasons for this expansion in range are discussed.

Context: Feral cats (Felis catus) prey on a wide range of Australian native bird species, with most records related to smaller, ground-dwelling or ground-nesting species. Aims: This study examined the impact of feral cat predation on endangered Carnaby’s cockatoo (Zanda latirostris), a large obligate hollow-nesting species. Methods: Cat predation was measured during a study into the breeding ecology of Carnaby’s cockatoo at a long-term study site in the northern wheatbelt of Western Australia. Key results: Feral cats predated Carnaby’s cockatoo adult females in their nest hollow, their nestlings, and eggs in at least three out of 38 years. When it occurred in those 3 years, the feral cat predation impact, expressed as a percentage of breeding attempts on cockatoo nesting were 5.2%, 11.6%, and 24.1%. The increase in predation rate in the year with the highest recorded rate coincided with the breeding season following an intense 8-month drought in mid-western Western Australia, which likely had an adverse impact on prey species more often consumed by feral cats. Conclusion: The results suggest that predation by cats can be a significant threat to Carnaby’s cockatoo because it reduces the survival of adult breeding females and recruitment of fledglings. Implications: Control of feral cats by local-scale shooting and cage trapping have both been used to achieve short-term success, offering a possible means of mitigating the long-term impact of feral cats at the study site, and potentially elsewhere.

Context: With climate change causing unprecedented and rapid changes, conservation agencies need to establish the impacts on vulnerable and threatened species to prioritise actions to minimise threats associated with those impacts. Aims: Carnaby’s Cockatoo (Zanda latirostris) is endemic to south-western Australia and this paper provides data to underpin future conservation management actions. Methods: We used data on the commencement of egg laying, breeding success, nestling condition, fledgling survival over their first year, and annual survival from the first year to construct a life table to examine the impacts of decreasing annual rainfall and increasing temperature in south-western Australia on the future viability of Carnaby’s Cockatoos. Key results: Long-term survival of Carnaby’s Cockatoos will be impacted by changes in rainfall, projected to be 16% drier in winter and up to 20% drier in spring, and by an increase in the number of days with maxima ≥35°C, conditions when the birds are unable to forage. Conclusions: This drying and warming is likely to lead to a further contraction in the range of Carnaby’s Cockatoo. Implications: Conservation management needs to address revegetation of foraging and breeding areas, repairs to derelict natural hollows and their maintenance, and provision of artificial hollows. Management should concentrate on areas with the best prospects for species survival and recovery including in the areas identified in this paper based on life table analysis and mapped across regions.

Context: Carnaby’s Cockatoo Zanda latirostris is an endangered species endemic to south-western Australia. It has been the subject of long-term studies of its ecology from 1969 to the present. Aims: This paper examines the maximum recorded life of the species in the wild. Methods: The life spans of eight wild Carnaby’s Cockatoos that were more than 20 years old were compared with longevity records of long-lived birds recorded on the banding registers in Australia, USA, and UK. Key results: Eight wild Carnaby’s Cockatoos were recorded living from 21 to 35 years, putting the species in the top 2% of all bird species in the wild for which there are longevity records. Conclusions: The longevity of Carnaby’s Cockatoo is similar to that of long-lived seabirds. Implications: Several years of immaturity and low reproductive output mean that Carnaby’s Cockatoos must be long-lived for the species to be sustainable. Conservation actions need to minimise threats to the lives of adult cockatoos.

Context: Carnaby’s Cockatoo is an endangered species and the subject of a recovery plan. Aims: Our study examined movements of adult and fledgling Carnaby’s Cockatoos from 11 breeding populations in southwestern Australia to establish where the cockatoos spent the non-breeding season (February–May) and sub-adult life-stage. Methods: Data were collected on point-to-point movements from re-sightings and recoveries of cockatoos individually marked with patagial tags or leg bands. Sites were mostly located in the wheatbelt of Western Australia. Distribution patterns in the breeding and non-breeding seasons, including nesting sites were derived from location data from the Department of Biodiversity, Conservation and Attractions’ Threatened and Priority Database. Key results: After breeding, adults and their fledglings moved from breeding areas to higher rainfall areas closer to the west and south coasts of south-western Australia where the food supply is greater and more reliable. Sub-adult cockatoos roam much more widely than adults and utilize foraging habitat not previously recognized as being important to this species. Conclusions: Important foraging habitat and locations have been identified for breeding populations in the north and south of the range of Carnaby’s Cockatoos. Implications: More conservation attention needs to be focussed on locating additional breeding populations, assessing the viability of these populations, and the extent and condition of their nesting and foraging habitat used during their non-breeding season. Conservation of Carnaby’s Cockatoo depends on the maintenance of remnant native vegetation and revegetation of nesting and foraging habitat throughout its range.

Context: This paper introduces the special issue of Pacific Conservation Biology devoted to the natural history of Two Peoples Bay Nature Reserve on the south coast of Western Australia. Methods: This paper provides the background to the special issue. Key results: Two Peoples Bay Nature Reserve was gazetted in 1967 for the conservation of the native biota, including two species; the Djimaalap/noisy scrub-bird (Atrichornis clamosus) and Ngilgaitch/Gilbert’s potoroo (Potorous gilbertii), both believed extinct for over 100 years before being rediscovered on the Reserve. The Reserve is 4774.7 ha in area, with wetlands, heathlands, granite outcrops, sand dunes, beaches, cliffs, and islands. Since it was established, mean annual rainfall has decreased by 16.8%, mean annual maximum temperature has increased by 0.2°C, and mean annual minimum temperature has increased by 0.7°C. Conclusions: The paper poses the question: what do the changes of drier winters, hotter summers, and more extreme weather events mean for managers of conservation areas such as Two Peoples Bay? Implications: Changing climate will pose problems for the managers of Two Peoples Bay Nature Reserve in ensuring the conservation of the Djimaalap/noisy scrub-bird and Ngilgaitch/Gilbert’s potoroo.

Context: This paper sets out the events leading to the establishment of Two Peoples Bay Nature Reserve. Methods: This paper is based on research into literature relating to the Albany region, government files and oral accounts relating to the area. Key results: Long known to the Noongar peoples, Two Peoples Bay was first mapped by Europeans in 1791 by Captain George Vancouver. The area was rapidly established as a base for the over-exploitation of natural resources. As the region became more developed and human population increased, recreational pressure on the area was such that the Western Australian Government surveyed Two Peoples Bay to establish a townsite. Just before the final surveys for the townsite were completed, the supposedly-extinct noisy scrub-bird (Atrichornis clamosus), was rediscovered there. National and international pressure on the WA Government from the conservation movement resulted in the reversal of the decision to develop a town in the area and led to the establishment of Two Peoples Bay Nature Reserve in 1967. Conclusions: The establishment of Two Peoples Bay Nature Reserve in the face of pressure for the development of a town on the bay, provides an interesting example of the needs of nature conservation over-riding real estate development. Implications: Although nature conservation values rarely stop real estate development, the Two Peoples Bay example demonstrates that nature conservation may prevail over real estate development, in this case involving the rediscovery of a species believed extinct.

A breeding population of Western Red-tailed Cockatoos Calyptorhynchus escondidus was studied between July 1974 and December 1981 at Nereeno Hill, in the northern wheatbelt of Western Australia. Egg-laying occurred during two clearly defined periods each year; with peaks mid-March to mid-April (Autumn breeding) and early-August to mid-October (Spring breeding). Thirty-two percent of the 459 eggs laid during the study were laid in Autumn and 68% in Spring. Growth rates of nestling wings and body mass were similar between seasons and years. Nearly one third of breeding attempts failed during incubation and 40.7% successfully fledged a nestling. Fledgling survival in the first year was low (17.5%), however, annual survival was higher after the first year; 80.0% after four years. Birds were killed by Wedge-tailed Eagles Aquila audax, shot by farmers, and drowned in stock troughs. Based on evidence from one individually-marked pair, Western Red-tailed Cockatoos may form long lasting pair bonds. While females breed every 12 months, some have bred in both Autumn and Spring seasons. Young Red-tailed Cockatoos remain with their parents up to two years after fledging, and adults may have young from two breeding seasons accompanying them. The breeding biology of Red-tailed Cockatoos is compared with that of closely related species from the genera Calyptorhynchus and Zanda. Threats to the species are loss of mature hollow-bearing trees and almost complete dependence on the seeds of Double Gee Emex australis, an introduced agricultural weed, for food.

The conclusions of our taxonomic review of the black cockatoos in the genera Calyptorhynchus and Zanda (https://doi.org/10.7882/AZ.2023.022) met with some opposition regarding our classification of the black cockatoos with yellow subterminal tail bands. We raised the three recognised subspecies to full species: Eastern Yellow-tailed Cockatoo Z. funerea Shaw, 1794; Western Yellow-tailed Cockatoo Z. whiteae Mathews, 1912; and Tasmanian Yellow-tailed Cockatoo Z. xanthanota Gould, 1838. Our separation of whiteae and xanthanota caused particular concern. In response to this concern, we re-analysed our data, using only anatomical data from adult specimens and demonstrate that there are valid grounds for the separation, with Z. xanthanota being significantly larger than Z. whiteae in 26 of the 30 anatomical measurements used in our analysis. We appreciate that our conclusion that Z. funerea, Z. whiteae and Z. xanthanota are separate species may not be readily accepted by all readers, but we would welcome any challenges backed by data.