• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
This species is recognised as separate from C. sulphurea and is assessed here for the first time. Despite an apparent recent stabilisation of this long-lived species's population, it remains unrecovered from its 1980s population size, when the species was being exported in its thousands annually from Sumba for the pet trade. The overall population reduction over the past three generations (43 years) is suspected to have been well over 80%. Even if the apparent mean stability of the population since 1992 continues, the scale of the reduction is sufficient that the rate of reduction will continue to meet thresholds for listing as Critically Endangered for several years to come. Recent information suggests that trapping is continuing and since 2017 has once again been increasing in intensity, with an associated increase in price per bird. Although the future rate of reduction is suspected to be at a lower rate, the resumption of trapping at a high intensity (from a much lower total population size) will be potentially severely impact the species in the near future.

Population justification
Due to previously being recorded only as a subspecies of Yellow-crested Cockatoo C. sulphurea, numbers of traded individuals of this subspecies are not precisely known, but it was estimated that in 1989 1,350-3,000 individuals were being exported from the island annually (Marsden 1995). In the 1980s two surveys took place with the aim of determining a harvest quota (PHPA/LIPI/BirdLife International 1998). In early 1986, a density of 8 birds per km² were recorded, and a population estimate of 12,000 individuals derived, while in 1989 the equivalent values were 1.8 birds per km² and 2,700 individuals (PHPA/LIPI/BirdLife International 1998). The total population was estimated at 3,200 in 1992 based on a density of 2.2 (plus or minus 1.1) individuals per km² in forest patches (1,080 km²) and around 800 elsewhere (Jones et al. 1995). Marsden (1995), placed the total population in 1992 at between 1,150 to 2,644 individuals. In 1989, the number of individuals being exported annually was estimated at between 1,350 and 3,000 (Marsden 1995), while CITES reported exports averaged 1,600 per year in 1991-1992 (WCMC, unpub. data collated from CITES annual reports, per Cahill et al. 2006). Consequently the species was considered to be at exceedingly high risk of extinction (Jones et al. 1995, BirdLife International 2001). From these values, it appears that the annual rate of decline exceeded 10% during the 1980s, and the total population reduction over this period exceeded 80%, which if it had been sustained would have led to the extinction of the species in under three generations. In 1992 and 1993, local decrees banned the trapping and transport of cockatoos on west Sumba and then east Sumba, and subsequently a zero quota for Indonesia was imposed for Cacatua sulphurea (sensu lato) in 1994. In 2002, densities in key forest patches had doubled from those in 1992 (Cahill et al. 2006), and the population outside of National Parks was estimated at 229-1,195 individuals (Persulessy et al. 2003). Overall, using equivalent area values to 1992 the population was likely between 2,000 and 5,200 individuals in 2002. The population has recently (2016-2019) been reassessed. The absolute minimum population size derived from direct observation of birds was 286 with a best value of 1,200 individuals extrapolated from sightings across the forest areas, while density estimate extrapolation indicated a tentative population size of 2,000 individuals, though this requires further evaluation of the assumptions of the extrapolation (A. Reuleaux in litt. 2021). The population is therefore estimated to number 800-1,320 mature individuals, which is suspected to still represent a reduction of greater than 80% over the past three generations.

Trend justification
Over the last three generations (1978-2021), the population of C. citriocristata is estimated to have declined rapidly. Population estimates from the late 1980s and early 1990s vary. Independently comparing the contemporary population estimate of c.2000 individuals (per A. Reuleaux in litt. 2021) to estimates of 12,000 individuals in 1986 (PHPA/LIPI/BirdLife International 1998) and 4,000 individuals in 1992 (Jones et al. 1995) suggests a decline rate equivalent to c.65-90% over three generations. Given the estimate of 1,350-3,000 birds being exported annually from Sumba in 1989 (Marsden 1995), and the substantially more abundant population size this implies, the rate of decline is suspected to be at the higher end of the 65-90% range. It is therefore suspected to have undergone a decline >80% over the past three generations (43 years). In recent years, this population decline has slowed. In 2002, densities in key forest patches had doubled from those in 1992 (Cahill et al. 2006), and the population outside of National Parks was estimated at 229-1,195 individuals (Persulessy et al. 2003). Overall, using equivalent area values to 1992 the population was likely between 2,000 and 5,200 individuals in 2002, suggesting that the population had stabilised or increased. The most recent population estimate however, of c.1,200-2,000 individuals in 2019 (per A. Reuleaux in litt. 2021) suggests that the population never recovered, and has plausibly declined slightly since. Recent reports of increased trapping (per A. Reuleaux in litt. 2021), including in protected areas, suggest that the species may be in decline once again but this requires confirmation with further surveys. Forest loss on Sumba is also accelerating: average annual forest cover loss averaged over the most recent 5 years (2016-2020) has been 0.8% (Global Forest Watch 2021), equivalent to a 34% reduction over three generations. The species is dependent on large trees for nest sites, and these trees are lost at a disproportionately rapid rate in comparison to general forest cover loss as the tree species are used for building or boat construction (Bashari 2013). Even if the slow declines of the population since 1992 continues, the scale of the reduction is sufficient that the rate of reduction will continue to meet thresholds for listing as Critically Endangered for several years to come. If trapping intensity does continue to increase, the species will no doubt be severely impacted within a few years once again, from a much lower population starting population.

Endemic to the island of Sumba, Indonesia, it historically occurred throughout the island and was considered an agricultural pest (Cahill et al. 2006). Heavily trapped for the pet trade, and for food, eventually prices began to rise in the mid-1970s and it became evident that a rapid population decline had commenced (Inskipp et al. 1988). The species occupied 17 of 33 remaining forest fragments in 1997 (O'Brien et al. 1997), but only 5 of these are larger than 2,500 hectares (Cahill et al. 2006). The Manupeu-Tanadaru National Park is the largest forest block.

Woodland and cultivated areas, usually in pairs or small groups. Breeding takes place from September to May on Sumba (Walker et al. 2005). It nests in tree cavities with specific requirements, tending to use a chink in the trunk or branch, or a pre-existing nest-hole made by another species, often in dead, snagged or rotting trees (Marsden and Jones 1997). May compete for available hollows with Rhyticeros everetti and Tanygnathus megalorynchos (O'Brien et al. 1997, A. Reuleaux in litt. 2021).

This species's precipitous decline is almost entirely attributable to unsustainable exploitation for internal and international trade. Illegal trapping continues  but has been reduced significantly from levels reported in the 1980s/1990s (D. Mulyawati in litt. 2012, A. Reuleaux in litt. 2021). Since 2017 an increase in trapping activity has once again been noted alongside an increase in the price trappers can obtain for each individual (A. Reuleaux in litt. 2021).

Large-scale logging and conversion of forest to agriculture across its range has exacerbated the decline, and forest cover loss within the range appears to be accelerating: if the average annual rate of loss from the past five years is projected forwards, loss would be in  the region of 34% over a three-generation period (data from Global Forest Watch 2021). Past forest cover loss have been around 18% over three generations (data from Global Forest Watch 2021). The species is dependent on large trees for nest sites, and these trees are lost at a disproportionately rapid rate in comparison to general forest cover loss as the tree species are used for building or boat construction (Bashari 2013). The depletion of these nesting trees exacerbates competition with other cavity-nesting species, notably Tanygnathus megalorynchus and Rhyticeros everetti (A. Reuleaux in litt. 2021).

At least formerly, the species was regarded as a crop pest, and consequently persecuted; and it may also be hunted for fun (H. Bashari in litt. 2016). A shift from cultivation of corn, papaya and other foodstuffs to rice on Sumba may also have reduced food availability for the species (Nandika & Agustina 2012). Competition for cavity nest sites with other parrots, hornbills and owls in large trees (those targeted by logging activities) may lead to reduced productivity (A. Reuleaux in litt. 2021).

Conservation Actions Information
CITES Appendix I (2005). This species (legislatively treated as conspecific with C. sulphurea) is considered a national priority in Indonesia by the Ministry of Forestry and Environment (H. Bashari in litt. 2016). Occurs in two national parks: Manupeu-Tanadaru and Laiwangi-Wanggameti. After precipitous declines, several populations on the island increased, or at least stabilised between 1992 and 2002 due to conservation efforts (including local education, eco-tourism and law enforcement) (Cahill et al. 2006) although densities remained below those typical of cockatoo species with an overall population that stabilised rather than recovered. This stabilisation appears to have held, with the population estimate in 2019 (per A. Reuleaux in litt. 2021) comparable to that in 1992 (although with much uncertainty). However, new information has recently indicated that trapping is continuing and has been increasing in intensity since 2017 with improving logistics for transport and communication, with an associated increase in price per bird. Moreover, illegal capture from inside protected areas has been documented since mid-2018 (A. Reuleaux in litt. 2021). A study into this species's breeding ecology has recently (2016-2019) been undertaken, and refinement of population estimates is ongoing (A. Reuleaux in litt. 2021).

Conservation and Research Action Proposed
The population size must continue to be monitored closely. Trapping and habitat loss pressures are currently anticipated to cause declines at a much lower rate (given approximate stability over the last 20 years) than previously. However, if trapping rapidly increases in intensity, from a much lower starting population, the species will likely be impacted within a few years once again. Law enforcement and monitoring are priorities for future work, as is the continued promotion of community-based conservation initiatives across the island. Remote sensing data should continue to be used to estimate rates of habitat loss on Sumba.

33 cm. A small cockatoo with long erectile orange crest and diffuse orange cheeks. Undersides of wing and tail are diffused yellow.

Text account compilers
Martin, R., Berryman, A.

Contributors
Reuleaux, A., Marsden, S. & Bashari, B.

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Recommended citation
BirdLife International (2024) Species factsheet: Citron-crested Cockatoo Cacatua citrinocristata. Downloaded from https://datazone.birdlife.org/species/factsheet/citron-crested-cockatoo-cacatua-citrinocristata 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.