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

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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

Adult Yellow-crested Cockatoo (Cacatua sulphurea).

The project exists to gather the information crucial
for the future conservation of Cacatua
. 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.

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

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.

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.
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

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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