Data Zone
Justification of Red List category
Reporting rates suggest a rapid population decline of >30% has taken place over the last three generations. The threats causing this are still ongoing and is therefore suspected to decline by the same rate in the future. For this reason the species is evaluated as Vulnerable.
Population justification
Using density and occupancy estimates, the population sizes of C. l. lathami and C. l. halmaturinus have been estimated at 6,000-10,500 (best estimate 7,500) and 230-290 (best estimate 250) mature individuals respectively. The population of C. l. erebus, however, has not been estimated. Based on areas of suitable habitat, it is suspected to number c.2,000 mature individuals, however there is substantial uncertainty with this. Combining these and account for these uncertainties, the total population is suspected to number 7,000-14,000 mature individuals.
Trend justification
Data are inconsistent (both in their trend and reliability) across the three subspecies.
Trend data for C. l. lathami up to 2019 indicate rapid declines over the past three generations. Reporting rates from 500-m radius area searches across their range, arguably the most reliable of the available survey methods for the species, declined by 59% from 1999–2019, equivalent to a decline of 79% in three generations. However, there was no significant change in reporting rates between 1977–1981 and 1998–2001 either nationally (Barrett et al. 2002), or in New South Wales (Barrett et al. 2007) and the 2-ha 20-min survey data from 1999–2019 (BirdLife Australia 2020) was too variable to provide a reliable trend. Similarly, the reporting rates derived from an annual Glossy Black-Cockatoo birding day event held since 2010 across south-eastern Queensland and far north-eastern New South Wales revealed that these are stable with no significant decline over from 2010–2017 (Cameron et al. 2021).
The population size and trend of C. l. erebus has not been estimated. Although the population has expanded its range to the Wet Tropics in the past 20 years (Garnett et al. 1999), high quality habitat at Eungella was badly burned in recent fires. Overall, the population of this taxon is believed to be comparatively small and probably stable (S. Garnett in litt. 2021).
The population of C. l. halmaturinus is tiny, hence although it has increased in the last three generations and effective management is expected to maintain the trajectory, its trend is unlikely to disrupt or affect the global trend.
Combining these analyses, Garnett & Baker (2021) inferred that the global rate of decline of this species is >30% over the past three generations and this is accepted here. Given the ongoing nature of the threats this rate is also suspected to continue in the future.
C. l. lathami occurs from Bundaberg in Queensland, Australia through eastern New South Wales to eastern Gippsland, Victoria. They have a continuous distribution through the forested parts of the Great Dividing Range but are more scattered inland where they occur as far west as the Riverina and Pilliga Scrub in New South Wales, and St George in Queensland. C. l. erebus occurs in the Wet Tropics in Queensland. C. l. halmaturinus occurs only on Kangaroo Island, South Australia.
C. l. lathami have an extremely restricted diet, eating only the seeds of a few species of Allocasuarina and, less often, Casuarina, favouring one or two species in any one region (Chapman 2007). They require large hollow-bearing trees for nesting, favouring areas with high densities of such trees (Higgins 1999, Cameron 2006b). While their strong bill gives them access to this nutritious, abundant and relatively stable food resource, intake rates are limited by handling time and cannot be accelerated if the food supply is short (Cameron 2005). The cockatoos lay a single egg in hollows in large old trees, particularly favouring dead trees (Cameron 2006b). C. l. halmaturinus feed almost exclusively on the seeds of drooping sheoak, preferring trees in which a high proportion of seeds contain kernels (Pepper et al. 2000, Crowley and Garnett 2001). Seed availability appears to be substantially lower after drought (Chapman 2005), in sheoaks more than 60 years old (Delzoppo 2018) and in trees <10 years old (Mooney and Pedler 2005) but planted sheoaks appear capable of producing seed more quickly than trees regenerating naturally (Cameron et al. 2021). When breeding, females lay a single egg in hollows in tall trees, particularly sugar gum Eucalyptus cladocalyx which are thought to take over 100 years to develop suitable nest hollows (Mooney and Pedler 2005) although many pairs now use artificial nest boxes (Berris 2016). Breeding birds return to the same nest site each year.
Historically, clearance of habitat has reduced the range of C. l. lathami, particularly south and west of the Great Dividing Range and much of their core habitat of the forests in the Great Dividing Range has been affected by fire. These threats also are likely to have caused the extirpation of C. l. halmaturinus from the mainland (Joseph 1982). While relatively few birds are likely to have been killed by the 2019–2020 fires, their food supply, already likely to have been diminished by drought (Cameron 2005, 2006b, 2009), will have depleted in burnt areas for at least a decade. Also, many nest hollows are sure to have been destroyed (Cameron 2009), especially in areas where the exceptionally dry conditions meant the largest trees in low parts of the landscape were destroyed. Any shortage of nesting hollows will increase competition from, for example, brushtail possums Trichosurus spp., which are responsible for high rates of nest failure of C. l. halmaturinus on Kangaroo Island (Garnett et al. 1999). The species also suffers from competition with introduced European honeybees Apis mellifera (Cameron et al. 2021). The regeneration of both allocasuarinas and potential future nest trees is impeded by grazing, either by stock or feral or native herbivores like rabbits Oryctolagus cuniculus, goats Capra hircus, and deer (NSW TSSC 2004, Cameron 2005). Furthermore, any loss of suitable nesting hollows may take many decades to replace. In coastal areas, residential development increasingly impinges on cockatoo habitat, although some birds acclimatise and feed in remnant trees. Although Psittacine Beak and Feather Disease has not been detected in wild Glossy Black-Cockatoos, the risk of spread from other cockatoo species, particularly those that compete for nests, is high (Sarker et al. 2014). Climate change in the form of increasingly intense heat waves (Herold et al. 2018), drought (Evans et al. 2017) and extreme fire weather (Di Virgilo et al. 2019, Dowdy et al. 2019), which all act synergistically, is also likely to affect the species within the next three generations.
Conservation Actions Underway
Nationally, C. l. lathami and C. l. halmaturinus are proposed to be listed as Vulnerable and Endangered respectively (Garnett & Baker 2021) and as threatened by all range states. Some populations are subject to targeted management and (especially halmaturinus) well protected with nests provided. Revegetation of feeding habitat on cleared land is occurring on Kangaroo Island, where there is ongoing monitoring of population size and nesting activity.
Conservation Actions Proposed
Obtain basic information on demography, occupancy, mobility, habitat requirements and threats responses. Assess breeding success rates and the factors that influence them across their range. Assess the availability and use of food resources and investigate the impact of the 2019–2020 fires and climate change. Improve protection of known and potential nest sites and foraging habitat during forestry operations and prescribed burning. Increase the extent and quality of foraging habitat. Ensure availability of water resources near food and nesting habitat for inland populations. Develop management plans for local populations to ensure resources are available to support viable populations in the long-term. Develop strategies to limit the impact of wildfire on feeding habitat. Develop strategies to rejuvenate senescent feeding habitat. Continue active management of nest sites, including reducing fire fuel loads. Continue population monitoring. Maintain active programme of community involvement.
Text account compilers
Berryman, A., Vine, J., Butchart, S.
Contributors
Garnett, S.
Recommended citation
BirdLife International (2024) Species factsheet: Glossy Black-cockatoo Calyptorhynchus lathami. Downloaded from
https://datazone.birdlife.org/species/factsheet/glossy-black-cockatoo-calyptorhynchus-lathami on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.