The Yellow-crested Cockatoo clings-on to its eastern fringe

February 21st, 2020 | by David Waugh
The Yellow-crested Cockatoo clings-on to its eastern fringe
Conservation projects

Imagine searching for a very rare species on scores of islands in an area of the tropics measuring 1,400 km between its north and south extremes, and the same distance again between its most eastern and western limits. Would anyone take on such a task? The answer is yes, because biologist Anna Reuleaux has taken-up the challenge to search for the Critically Endangered Yellow-crested Cockatoo (Cacatua sulphurea) within an area of those dimensions. Hardened to the duress of field conditions, Anna is the principal investigator and doctoral student in a project by Manchester Metropolitan University, UK in collaboration with Burung Indonesia, the country representative of BirdLife International. The project has been running since the second half of 2016, and is supported by the Loro Parque Fundación, with additional support from the Zoological Society for the Conservation of Species and Populations. 

Adult Yellow-crested Cockatoo (Cacatua sulphurea).

The project exists to gather the information crucial for the future conservation of Cacatua sulphurea. Of its several objectives, a vital one is to conduct surveys of remaining cockatoo populations across the entire geographical distribution of the species, to produce accurate estimations of local population sizes, and to determine their ecological requirements and need for interventions. Areas are being identified which have, or could have, the right conditions to be sites for future interventions or re-introductions. Like other Asian cockatoos, Yellow-crested Cockatoos have been particularly affected by over-exploitation for trade, as well as loss of their forest habitat. Indications are that the species has disappeared from almost all of its geographical distribution, a situation affecting all seven subspecies (recognised since 2014), all in the biogeographical region of Wallacea except for C. s. abbotti on the Masalembo Islands.

Historic Cacatua sulphurea records 1856-2016. The seven subspecies (recognised from 2014) are coded by colour. Most sites are certain to have no cockatoos today.

Anna has already travelled through many islands, and has concentrated her survey efforts on the locations with the highest likelihood of populations surviving. She has not needed to survey locations with a known absence of cockatoos, nor those with known populations surveyed recently by other researchers. She has been able to confirm that the current most important strongholds of the species are the islands of Sumba, where C. s. citrinocristata is endemic, and Komodo where a population of C. s. occidentalis is found. Awaiting her attention have been locations along the eastern fringe of the Yellow-crested Cockatoo’s distribution, and her most recent field excursion has been to survey those remaining sites, taking her to West and East Timor (C. s. parvula), south-east Sulawesi and Buton (C. s. sulphurea), and the Tukangbesi (Wakatobi) islands (C. s. paulandrewi). Romy Limu, who has been working with Burung Indonesia for more than five years, accompanied her as field assistant.

Anna Reuleaux (left) and field assistant Romy Limu (second from right) with field staff of the BKSDA (Natural Resources Conservation Centre) in West Timor.

Survey locations were initially selected based on reports and records in digital and printed literature, and prior to field work Anna and Romy consulted each local conservation office (BKSDA – Natural Resources Conservation Centre) about recent cockatoo sightings. Promising areas were then visited, and leads followed from village to village until cockatoo presence or absence could be confirmed. For fragmented habitat, minimal abundance of cockatoos was estimated by counting the maximum number of individuals sighted at one time, and where larger or several flocks were suspected, searches for communal roosts were undertaken to attempt observation of all individuals simultaneously. More sophisticated counting methods were only suitable for the largest and densest cockatoo populations.

The surveys began in the island of Timor, of which the western half belongs to the Republic of Indonesia and the eastern half is the Democratic Republic of Timor Leste (East Timor). Differences between the two in conservation laws, administration, law enforcement and trade connections seem to make a big difference to the survival of cockatoo populations. Trade and travel from East Timor to Indonesia is highly controlled, effectively excluding the East Timor bird populations from the Indonesian bird market. Bird trapping was very common during the Indonesian occupancy but has almost ceased now. However, in the same period hunting birds for food became normal and consequently shooting cockatoos opportunistically when hunting pigeons is more common in East Timor than trapping them.

Anna and Romy observing Yellow-crested Cockatoos flying over a mangrove-covered island Tourism Nature Reserve in West Timor.

At four locations in West Timor, the cockatoos reported by others totalled between 125 and 128 individuals, with a minimum flock size of three and the largest maximum flock of 47 cockatoos, observed on the island of Rote. Anna and Romy could only visit two locations, with a total count of 51 cockatoos. A diversity of habitats were used by the cockatoos, including dry lowland forest, coastal forest, mangroves, degraded primary and secondary forest remnants, and plantations. Three locations had some kind of protected area status, and the fourth had no formal protection by law but the cockatoos there are protected by traditional beliefs instilled in the community by the village head, an ex-trapper who decided 30 years ago to save the cockatoos instead. At two sites the cockatoos are monitored annually by the conservation authorities, and there is opportunistic monitoring by local communities at the remaining sites. Cockatoos commuting daily to adjacent plantations outside of a protected area run the risk of being shot or trapped, but the main threats include further habitat degradation and resulting nest site shortage, encroachment of agriculture into protected areas, and infrastructure development for tourism.

Primary forest cockatoo habitat in the highlands of East Timor.

At six locations in East Timor, a total of between 179 and 206 cockatoos were sighted, and the largest flock was of 55 and the smallest of four individuals. Once again there was a variety of habitats from mangrove and savannah interspersed with gardens and forest patches, through mixed cultivation and coffee plantations, to largely or entirely primary forest and montane tropical forest. Three locations had no protection, but the other three were in national parks. In one of those, the Nino Konis Santana National Park, the cockatoos appear to form one large continuous population, because the habitat is not as fragmented as in nearly all other surviving populations of the species. Anna and Romy could only obtain an absolute minimum estimate of the population, and more research is needed at this location. The population is probably the third largest of the species (after Sumba and Komodo) and relatively well protected in a national park, in the far corner of a country without a commercial cockatoo trade. Furthermore, reports of direct encounters with cockatoo from mountainous zones suggests that cockatoos could still be widespread in less populated higher altitude areas. However, threats which require vigilance are the potential intensification of trapping, shooting and agriculture, and the encroachment of cultivation into primary forest.

Hunting trophies in Nino Konis Santana National Park, East Timor, where hunting is theoretically forbidden.

Sulawesi is the largest island in the distribution of C. sulphurea, but alarmingly might have the smallest population of the Yellow-crested Cockatoo, with the nominate subspecies among the closest to extinction. The only confirmed cockatoo populations are on Pasoso Island, to the north-west of Sulawesi, and in Rawa Aopa Watumohai National Park, south-east mainland Sulawesi. Inside this large park there is only a very small area where cockatoos can be encountered more frequently. Anna and Romy surveyed five locations in that region, observing a maximum flock of 11 individuals at one site and failing to find any at two other sites. Reports from other observers give a total of only 21 individuals counted across the five locations. The national park authorities seem incapable of preventing illegal logging for cultivation, plantations and other activities in the centre of the forest, such that this habitat is very fragmented, in some areas functioning only as a corridor. Furthermore, there are ownership claims by an established village community inside the park, and villagers report that outsiders come every year to capture wild C. sulphurea.

Fruit of the Java olive (Sterculia foetida) dropped by feeding Yellow-crested Cockatoos.

Anna and Romy visited eight areas on Buton, an island which still has relatively large areas of forest, but failed to find any cockatoos, and all local reports were discouraging about the possibility that the species still survives there. They moved on to the Tukangbesi Archipelago, which is contained in its entirety within the Wakatobi Marine National Park.  Islands inhabited since before the creation of the park receive no protection under the national park status, but uninhabited islands function to protect terrestrial biodiversity. Although the Yellow-crested Cockatoo does not feature in the plans and reports of Wakatobi National Park, the remnant populations are known to the local national park staff.

To observe cockatoos, the ridges of Gunung Modus give a view over the central forest of Rawa Aopa Watumohai National Park, Sulawesi.

Cockatoos were recently reported by other ornithologists on four islands in the archipelago, and Amy and Romy confirmed presence on three of those islands, with a maximum flock size of 18 individuals.  A previous maximum flock size of 50 was recorded, contributing to a total count of only 69 cockatoos across the four islands, but high encounter rates indicate a more sizeable population. One of the locations had primary forest, mangrove belts and emergent trees among plantations, and logging there is regulated due to traditional beliefs and access is forbidden. However, most locations have highly modified habitat, mainly coconut and banana plantations, interspersed with small forest remnants, sparse woodland with emergent trees, and mangrove forest. Therefore, the main concerns are the potential intensification of agriculture if the terrestrial areas of the national park are not protected better, ongoing capture of adult cockatoos, and competition by introduced parrot species.

A pair of Cacatua sulphurea paulandrewi in Tukangbesi.

The diligent searching of this project has revealed that the Yellow-crested Cockatoo has a better chance in some parts of its eastern fringe, but is barely clinging-on in others. Without urgent action the long-term viability of the smallest populations is very unlikely. It is now with great anticipation that the project makes its key recommendations to boost the protection of the species in all its areas of occurrence.

Author: David Waugh, Correspondent, Loro Parque Fundación

Title photo: Anna Reuleaux/MMU

Credit other photos: 1 – C. Lam, 2-9 -Anna Reuleaux/MMU


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