Yellow-Crested Cockatoo: Endangered Species Spotlight

Easily recognised by its resplendent yellow crest and gold-tinted blush – or perhaps more so by its raucous squawk – the yellow-crested cockatoo is one of 21 species of cockatoo (family Cacatuidae) in the order Psittaciformes (parrots). Although endemic to Timor-Leste and Indonesia, where populations were previously found throughout Nusa Tenggara, on Sulawesi and its satellite islands, and on the Masalembu Islands, the species has suffered rapid population declines due to rampant trapping for the exotic pet trade. Having been driven to extinction in a substantial portion of its former range, the yellow-crested cockatoo is currently classified as critically endangered. Incredibly, feral populations of several hundred birds exist in the highly urbanised cities of Hong Kong and Singapore, as well as in China, which could potentially play a significant role in the recovery of the species worldwide. However, for such conservation efforts to succeed in the long term, primary threats such as poaching and habitat loss must first be eliminated in the endemic range of the species.

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1. Appearance

The yellow-crested cockatoo, also known as the Lesser Sulphur-crested cockatoo, is a medium-sized species measuring approximately 33 to 35 centimetres in length when fully matured. It is often confused with the larger and more common Sulphur-crested cockatoo (Cacatua galerita), which is found in Australasia and is distinguishable by the absence of yellow patches beneath its eyes. Although subspecies of the yellow-crested cockatoo are generally regarded as synonymous, apart from the notably larger Cacatua sulphur abbotti, recent studies have uncovered significant morphological differences between the birds, as well as possible subspecific division within Cacatua sulphur djampeana. The citron-crested cockatoo (Cacatua citrinocristata) was previously recognised as a subspecies of C. sulphur but was subsequently regarded as a separate species, given its orange hue.

The adjustable, forward-curling feather crest of a yellow-crested cockatoo is a magnificent shade of yellow, flaring up as a form of both intraspecific and interspecific communication when the bird is alarmed, excited, aroused or threatened. It is also theorised that the crest makes cockatoos appear larger to potential predators, serving as a defence mechanism. The two patches of yellow feathers beneath the eyes of yellow-crested cockatoos are ear-coverts – patches of feathers that cover the bird’s ear openings, since the ear of a bird has no external features. The species also has a yellow wash on the underside of its wings.

Like other cockatoos, the yellow-crested cockatoo has a stout, curved bill. This curved beak shape lends greater holding power than a straight beak would, allowing the bird to crack nuts and hard seeds, prune leaves, scoop fruit pulp, scrape the bark off trees, and dig up earth. All members of the Psittaciformes order also share zygodactyl feet, where the first and fourth digits face backwards while the second and third digits face forwards, providing these birds with an incredibly strong grip and excellent climbing abilities. Short tails further confer the speed and agility necessary to navigate dense forests.

Cockatoos are typically less colourful than other members of the parrot order, with most species under the genus Cacatua sporting all-white plumage. This is primarily caused by the lack of Dyck texture in their feathers, which typically produces blue and green colours in the plumage of other parrot species by the way in which it reflects light. 

2. Diet

On the small Indonesian island of Masakabing, research has shown that yellow-crested cockatoos preferentially consume breadfruit (Artocarpus communis, a species of flowering tree in the mulberry and jackfruit family), the fruit and flowers of coconut palms (Cocos nucifera), young leaves and flowers from kapok trees (Ceiba petandra) and mangroves, as well as the seeds, flowers and fruit of at least six other species of flora. More generally, the diet of the species consists of seeds, nuts, roots, fruit, leaf buds, shoots, and flowers, depending on the season and geographic location of the bird. Its zygodactyl feet, muscular tongue and strong, curved beak allow the yellow-crested cockatoo to crack hard nuts, de-husk seeds, and manipulate its food with relative ease.

3. Habitat & Behaviour

Endemic to Timor-Leste and Indonesia, the yellow-crested cockatoo was once found throughout Nusa Tenggara, Sulawesi, and the remote Masalembu Islands in the Java Sea. After decades of drastic declines due to trapping and habitat loss, small populations are now confined to the South-east Sulawesi province, one island in Central Sulawesi, and three satellite islands to the south. Notable populations continue to occur on West Timor and Timor-Leste, as well as the Flores Sea and Sumbawa island groups, including a group of approximately 1,000 individuals on Komodo Island. The species has been extirpated from several islands in the Lesser Sundas, Masalembu Island, and Lombok. With only 17 to 22 individuals remaining in the wild, the subspecies Cacatua sulphur abbotti is among the rarest and most threatened cockatoos, found only on Masakambing Island in the Masalembu Archipelago. A feral population of several hundred birds can be found in Hong Kong, China and Singapore, with these birds displaying an incredible ability to survive outside their natural range and preferred habitat.

Yellow-crested cockatoos typically inhabit evergreen, moist deciduous, monsoon and semi-evergreen forests, forest edges, scrubland, and agricultural land. The species can be found at altitudes of up to 500 metres on Sulawesi, and between 800 and 1500 metres in Nusa Tenggara. Although previously believed to require closed-canopy primary forest to thrive, populations in Sulawesi have been observed inhabiting forest savanna and open habitats rather than primary forest. As mentioned, drastic adaptations are also seen in the feral cockatoo populations of Hong Kong and Singapore, where these birds have survived as an introduced species in highly urbanised environments with limited forest coverage.

Females nest in tree cavities with specific requirements, typically opting for a pre-existing nest hole or chink in the trunk of a dead, snagged or rotting tree that is optimally over 100 years old. Nomadic by nature, cockatoos travel in groups or flocks to areas where food stocks are abundant, flying and foraging diurnally before returning to their home roosts for the evening.

In addition to the feather crest, vocalisations are used extensively by cockatoos for intraspecific communication. From single harsh screeches and loud, raucous calls, to sweeter whistles and squeaky notes, these vocalisations may serve as a form of individual identification within flocks, as well as to warn others of a potential threat or danger, to express emotion, to stay together, and to protect their nests. Loud calls are a particularly useful adaptation for cockatoos who live in thick, dense forests, as birds in a flock can communicate over long distances without the need to locate each other.

Members of the Psittaciformes order, together with those in the family Corvidae, are considered to be the most intelligent of birds. This is due to the fact that these species have a brain-to-body size ratio equivalent to higher primates. Early childhood learning appears to be of critical importance to cockatoos and is primarily social in nature. Playing, predator avoidance, and foraging are important aspects of learning, ordinarily taught by siblings, flock members and parents. Insufficient stimulation may result in young birds developing destructive behaviour, which often occurs when these species are kept as pets.

4. Ecological Importance

Although researchers have yet to fully understand the specific role that yellow-crested cockatoos play in their native ecosystem, the herbivorous diet and nomadic nature of the species indicates that it plays a part in seed dispersal and the distribution of plants. The yellow-crested cockatoo further occupies a place in the food chain, with its eggs and chicks serving as prey for Komodo dragons (Varanus komodoensis), as well as two birds of prey: the spotted kestrel (Falco moluccensis), and the white-bellied sea eagle (Haliaeetus leucogaster). Komodo dragons and yellow-crested cockatoos also compete for nesting space on Sterculia foetida trees, with Komodo dragons often invading the nests of yellow-crested cockatoos during their arboreal phase.

5. Threats

Following intensive surveys conducted between 2016 and 2019 across Indonesia and Timor-Leste, researchers determined that the total population of yellow-crested cockatoos left in the wild numbered approximately 1,800 to 3,140 individuals, or 1,200 to 2,000 mature individuals. Despite limited data on the species’ population size prior to 1980, the sheer extent of the commercial trade in yellow-crested cockatoos in the 1980s and 1990s, fuelled by an intense and inexplicable demand for the mischievous bird as a pet, has led conservationists to suspect that the once widespread species has suffered population declines of 80-90% over the past three generations. As a result, the yellow-crested cockatoo has been classified as ‘Critically Endangered’ under the International Union for Conservation of Nature (IUCN) Red List. Although future declines are predicted to occur at a much slower rate, given that the majority of remaining populations are concentrated in protected areas, the threat of trapping, as well as the growing threat of deforestation, continue to pose a significant risk of extinction to small, isolated populations. 

In the last quarter of the 20th century, demand for yellow-crested cockatoos as pets soared internationally, creating a financial incentive for the trapping and sale of wild birds. Throughout the 1980s, between 5,200 and 12,000 yellow-crested cockatoos (figures include C. citrinocristata as a subspecies) were imported to Singapore annually, and an estimated 96,000 individuals were exported from Indonesia between 1981 and 1992. Although trapping the species became illegal in Indonesia in 1990 under the Conservation Act, and while trapping rates have decreased from historic levels in the 1980s, the commercial trade of yellow-crested cockatoos has continued domestically and internationally due to poor enforcement and monitoring. This is particularly true of the smaller Indonesian islands of Rote, Alor, and Pantar, where capacity for the enforcement of regulations prohibiting hunting and trade is limited. In 2015, Indonesian authorities seized a suitcase containing 23 yellow-crested cockatoos and one green parrot that had been stuffed into plastic water bottles. The alleged wildlife smuggler was apprehended at Surabaya Port, Java, where officials typically search every ship for illicit smuggling activity despite limited manpower. Given the discretion to impose fines of up to 100 million rupiah (US$6,800) and prison sentences of up to five years on those convicted of trapping a protected species under the 1990 Act, some claim that courts rarely impose fines greater than 10 million rupiah (US$690) or sentences greater than 18 months. Such penalties amount to a mere fraction of the income that poachers receive for the sale of wild cockatoos, which, coupled with inadequate monitoring and apprehension by law enforcement, leaves them with little reason to fear retribution. 

In 2005, the yellow-crested cockatoo was listed under Appendix I of the Convention on International Trade in Endangered Species (CITES), thereby banning the commercial trade of the species.

Nevertheless, due to a legislative grey area, cockatoos can still be traded legally if they originate from a captive breeding facility, rather than having been caught in the wild. The issue with such a caveat is that identifying the difference between wild-caught birds and captive-bred birds is incredibly difficult in practice. Although some countries have methods for distinguishing the two, such as in Hong Kong where captive-bred cockatoos must be tagged with a leg band and ID number, monitoring and enforcement practices are often inadequate. According to Astrid Andersson, a postdoctoral researcher at Hong Kong University who specialises in cockatoos, surveys of Hong Kong’s Yuen Po Street Bird Market revealed that some birds were not wearing a band, or had one that could be removed or that did not display an ID number. In a visit conducted by CNN to the same bird market in May 2023, yellow-crested cockatoos spotted on display were said to be pets. However, after expressing interest in purchasing a cockatoo, shopkeepers claimed to be able to source a yellow-crested cockatoo for HK$28,000.

While the Hong Kong Government’s Agricultural, Fisheries and Conservation Department (AFCD) has stated that the last commercial import of yellow-crested cockatoos occurred in 2004, and that there are no CITES-registered breeding operations in the city, there remains the possibility that home-breeding occurs amongst private pet owners. In recent years, Facebook has become a popular platform for the trade of exotic pets, such as cockatoos, as the practice is slightly more covert. WWF Hong Kong tend to monitor online groups for the trade of protected birds, often observing young chicks being sold. The organisation has noted that traders typically require buyers to send private messages, or utilise cryptic keywords to disclose the price of the bird, such as its flying distance. 

Since the 1980s, conservationists have largely regarded trapping as posing the greatest threat of extinction to wild yellow-crested cockatoo populations across Indonesia and Timor-Leste. However, as remaining populations are now largely concentrated in protected areas and legislative measures have rendered commercial trade more difficult, a new and growing threat has come to light: deforestation. Extensive logging and the conversion of primary forest to agricultural land has affected the diversity of flora found across the species’ native ecosystems, altering the availability of food sources and exposing cockatoos to a greater risk of predation and poaching. Based on studies conducted by the Global Forest Watch in 2021, which estimated the mean annual rate of forest cover loss over the previous five years, researchers have projected a forest loss rate of approximately 16.1% across the current occupied and probably occupied range of yellow-crested cockatoos over the next three generations. Although the yellow-crested cockatoo has proven adaptable to land conversion and varied habitats, the the species’ dependence on large, old trees with substantial hollows for nesting, typically found in old growth forest, has led researchers to estimate population declines of 30 to 49% over the next three generations.

For Flores Sea island cockatoo populations, agricultural conversion is currently considered to be a primary threat, while poaching for local consumption, rather than for the pet trade, has been identified as a secondary threat. On Komodo Island, juvenile Komodo dragons compete with cockatoo chicks for nesting sites, with deforestation and loss of forest cover further exposing nestlings to predation by large birds of prey. Studies on the citron-crested cockatoo (C. citrinocristata) have identified competition with fellow parrots and owls for nesting sites in large, hollow trees, primarily in areas targeted by logging, as a primary cause of low productivity. Given the similarities in ecology between citron-crested and yellow-crested cockatoos, some have speculated that such competition may also affect the productivity of the latter species. Yellow-crested cockatoos have also been observed raiding agricultural plots, consuming ripened crops or digging up newly sown seeds, as natural food sources become increasingly scarce. As a result, some communities view cockatoos as pests, not only exposing the birds to conflict or retaliatory acts, but also reducing local support for their conservation. 

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6. Conservation

In addition to listing the yellow-crested cockatoo under Appendix I of CITES in 2005, a cooperative recovery plan was implemented by signatories, and the species’ recovery was declared a national priority by the Ministry of Forestry and Environment of Indonesia. Although governmental conservation efforts have largely been limited to legal protections, the establishment of protected areas and national parks with intensive safeguarding measures have had some success. On Sulawesi, the removal of overhanging vegetation and the installation of plastic collars around the trunks of nesting trees have reduced the threat of predation for cockatoo nestlings. In Komodo National Park, the yellow-crested cockatoo population of over 1,100 individuals, arguably the most important population at present for recovery efforts, is currently stable and well-protected. In some regions, mangrove restoration projects are also underway in an effort to improve the availability of nesting habitats for cockatoos.

Given the implementation of legislative regulations limiting international trade in yellow-crested cockatoos, domestic trade likely accounts for a large proportion of the current market. Organisations such as the World Parrot Trust have therefore promoted community engagement programmes and local education initiatives to reduce trapping and foster conservation. These projects have included providing communities with binoculars and field guides to encourage parrot watching, as well as suggesting ecotourism projects, such as locally-guided birding trips.

In 2008 and 2009, surveys conducted by the Indonesian Parrot Project led to meetings with community leaders, villagers, police and local military on the islands of Masakambing and Masalembu in an attempt to raise awareness about the plight of yellow-crested cockatoos, shed light on the species’ ecological importance, and encourage engagement in its conservation. Schools across the Masalembu Archipelago and in south-east Sulawesi have embraced Conservation Awareness Pride programmes, engaging both adults and children in understanding the importance of protecting local ecosystems and endangered species. Additionally, a ‘village regulation’ was implemented to prohibit the trapping, ownership or transportation of yellow-crested cockatoos, and to initiate measures to reduce habitat disturbance. By employing a former village head to enforce the regulation, monitor nests and study the species, this locally-mediated policy has enabled the local population of yellow-crested cockatoos to increase by nearly threefold over a period of 12 years. Similar community-led initiatives have been implemented in the Moronone community of Sulawesi, where four Forest Wardens are tasked with monitoring the species and prevent trapping. To reduce conflict between farmers and cockatoos, it has been suggested that additional or ‘sacrifice’ crops could be planted to compensate for losses, such as sunflower fields which typically attract the attention of cockatoos away from other crops.

In Hong Kong, where the international trade of yellow-crested cockatoos has proven to have remained active, efforts are underway to create unique strategies for reducing the illegal trade. Astrid Andersson, a postdoctoral researcher at the University of Hong Kong’s conservation forensics laboratory, has developed a forensic tool that could help distinguish between captive-bred and wild-caught cockatoos in Hong Kong. Wild cockatoos consume a wide variety of seeds, leaves, shoots, flowers and fruits, whereas captive cockatoos tend to receive a diet high in corn, which has a distinctive carbon ratio. By using a “stable isotope analysis” to examine the carbon and nitrogen in the feathers of any given cockatoo – a test which is inexpensive and takes only one week to yield results – authorities could potentially determine whether cockatoos sold at pet markets were recently taken from the wild. 

Now, Andersson has focused her efforts on the genetic analysis of Hong Kong’s yellow-crested cockatoo population to determine their origins. By extracting tissue samples from local birds and comparing their DNA with that of museum samples from the species’ natural range, Andersson hopes to determine whether Hong Kong’s cockatoos are inbred, hybrids, or pure subspecies from a specific region in Indonesia. The analysis could further shed light on the age and genetic health of the local population. While this information could help with understanding Hong Kong’s yellow-crested cockatoos, potentially providing insights into the species’ ecology in general, the analysis could also indicate whether the city’s population could assist with genetic rescue in Indonesian populations should it be needed.

While conservation initiatives implemented thus far have had success in safeguarding yellow-crested cockatoo populations remaining in the wild, as well as in garnering public interest in their protection, the IUCN has noted further conservation and research actions that have been proposed for the species. These include: strengthening law enforcement in protected areas and monitoring trade in key locations; promoting widespread community-based conservation initiatives, particularly on small islands; monitoring population trends and identifying critical areas for protection; maintaining regular patrols, raising awareness in local communities, and studying the impact of human activities on the species within Komodo National Park; conducting further ecological research to develop better strategies for the species’ management and conservation; studying the abundance of nest holes and water sources; and monitoring forest loss within the species’ range.

NGO Spotlight: Indonesian Parrot Project

Founded in 2001, the Indonesian Parrot Project (IPP) is dedicated to conserving Indonesian cockatoos and parrots through projects both in the field and across local communities. In 2004, after a smuggler was apprehended on Seram Island with a number of parrots and cockatoos, a collaboration between the National Park of Manuela and the IPP resulted in the establishment of the Kembali Bebas Avian Rescue, Rehabilitation and Release Centre. With the support of private donors and grant money, the IPP expanded the facility to include 60 cages and an on-site avian medical clinic, receiving birds seized from smugglers and preparing them for release. In 2008, the project was turned over to the local community, with continued involvement from the IPP to locate funding, and the facility continues to improve its resources for the care and eventual release of trapped birds. 

As mentioned, the IPP also designed and implemented a Conservation Awareness Pride (CAP) Programme, designed to educate children about cockatoos and parrots across Indonesia, their importance to the ecosystem, and to foster a genuine interest and passion for conservation in young generations. By raising awareness on the inhumane effects of trapping, the exotic bird trade, and the lasting effect that population declines can have on the environment, as well as highlighting how incredible cockatoos are as a species, the CAP programme aims to instil a sense of pride in local communities and garner a strong desire to protect their surrounding environment. The programme includes: cockatoo colouring books, t-shirts and posters; murals; city signs; drawing contests; songs; TV and radio presentations; and trips to the Kembali Bebas Rehabilitation Centre to witness the release of birds.

The IPP has also facilitated a participatory process to introduce and establish small business opportunities that address the needs of local communities and operate on their values, traditions, and customs. By providing training, mentoring, services, and motivation to locals who may otherwise rely on the trapping of wild birds to secure an income, communities are able to build sustainable sources of income for themselves with the support of the IPP, achieving financial self-reliance while promoting ecologically friendly economic development. Some alternate avenues of sustainable income introduced by the IPP include: hiring forest wardens to monitor and protect nests; supporting businesses led by local women, such as arts, crafts, and organic farming; and hiring local guides for ecotourism projects.

The IPP also conducts scientific studies on Indonesian cockatoos and parrots, such as genetic analyses, censuses, breeding analyses, and studies on their nesting behaviours and food requirements, to better understand the ecological needs of these species. Such data not only helps with the care of birds in rehabilitation, but also supports the design of data-driven, efficient conservation actions. Lastly, in collaboration with both governmental and non-governmental agencies, the IPP monitors the illegal trade of cockatoos in an attempt to reduce trapping and smuggling.