The Indonesia and Timor Leste’s endemic bird, Yellow-crested Cockatoo (Cacatua sulphurea), is now in critically endangered (CR) status. It used to be easily found in Lesser Sunda Islands and Sulawesi. Elders in some villages still remember their parents ordering them to hunt cockatoos to protect their corn fields, but nowadays children hardly ever see the bird at all thanks to the decrease of its population.
Anna Reuleaux, a Germany researcher who is currently pursuing a doctoral study at Manchester Metropolitan University, has spent most of her life researching the development of the small yellow-crested cockatoo in Indonesia. He has traveled to many important habitats for cockatoos in the Wallacea area, especially on Sumba Island.
The ladder to access the cockatoo nest still stands on Pantar Island, Alor.
Anna's research aims to provide a knowledge base for conservation action on this charismatic bird, including finding the distribution of the remaining population of cockatoos in the Lesser Sunda Islands and Sulawesi, quantifying their numbers and, most importantly, understanding why this species is able to survive in some locations but disappears in others. Investigating the developmental outcomes of this species, including its inhibiting factors, is also important for understanding the survival or vulnerability of cockatoo populations. To carry out the research, Anna passionately rides her motorbike to various places in the Lesser Sunda Islands.
Perkembangan populasi di Tanah Sumba
One of the largest populations of Yellow-crested Cockatoo’s subspecies, the Citron-crested Cockatoo (Cacatua sulphurea citrinocristata), is inhabiting Sumba Island of East Nusa Tenggara with the latest count 1000 individuals (Cahill et al. 2005). Burung Indonesia cooperated with the Fund for Endangered Parrots, a working group of ZGAP, on awareness activity on biodiversity sustainability in Sumba. The collaboration led to the creation of the Manupeu Tanah Daru National Park and stopped hunting for “the orange-crested one.”
The largest cockatoo perch on Sumba Island
Survival ability was not the only parameter assessed on the research. The demography and cockatoo’s reproduction inhibitors were also important. Therefore, Anna and Burung Indonesia’s team conducted monitoring during the primary breeding period of cockatoo—October to March.
Active cockatoo nests were hard to locate, but by increasing the search during the season in 2015-2016, Anna and the team managed to find 19 of them. Unfortunately, there were only five eggs on the nests and only one hatchling survived.
Anna and the team found a juvenile with head protruding out the nest, indicating its readiness to be a full-fledged bird. But on their next visit they found its bones, with the head skull was nowhere in the nest, suspected of being attacked by a predator before it could learn to fly. The finding crushed Anna’s heart.
This cockatoo died before being able to fly, suspected of being preyed on by a predator.
Disappointed with the results they found earlier in the season, Anna and the team installed a camera trap above the entrance of the nest in the 2016-2017 season and found two pairs of Citron-crested Cockatoos inhabiting unmonitored nests. All birds on the latest phase of breeding and not doing many activities. A pair successfully raised two juveniles, making it the first finding on a monitored nest in Sumba.
Anakan kakatua sumba di dalam lubang sarang.
Camera trap recording from inside the nest provided evidence of potential competitors and predators for cockatoos. Common Long-tailed Macaque (Macaca fascicularis) and Common Palm Civet (Paradoxurus hermaphroditus) were caught on camera monitoring the cockatoo nest hole, which was empty at the time. Two owl species were known using the same nest at night regularly, while Short-tailed Starling (Aplonis minor), Great-billed Parrot (Tanygnathus megalorynchos), and Sumba Eclectus (Eclectus roratus) control the location of abandoned cockatoo nests.
A number of Sumba birds are interested on cavities; a Sumba Hornbill was captured in the photo inspecting a cavity
Where are the other cockatoo populations?
There are six subspecies of Yellow-crested Cockatoo in Sunda Lesser Islands, Sulawesi Island and three small islands in Sulawesi and Java Sea. During the period of March-May 2017, Anna went on a road trip on her motorcycle to observe the population of Yellow-crested Cockatoo subspecies in the islands between Sumbawa and Alor. The remaining largest population was inhabiting Komodo National Park. [1]
The condition of the track to the potential location of the cockatoo population on Sumbawa Island
There were 70 recorded sites with the presence of Yellow-crested Cockatoo between Sumbawa and Alor, although most of the birds now can no longer be found. Anna and the Bird Indonesia Sumba Program team surveyed the most potential locations, calculated estimated numbers, and found suitable conditions that would allow the cockatoo population to survive.
The team was able to find surviving cockatoo populations in 15 locations, numbering from four to 46 individuals. Evidence of cockatoo capture was seen in almost all population locations: cockatoo rearing in villages, community reports of bird 'harvesting', or visible climbing equipment on nest trees.
Cockatoos survive in areas that are difficult to reach, such as this location on Alor Island.
Various reasons cause this population to survive and every place has its own story, but the most common reason is that it’s protected from hunting for trading commodities.
This may also be due to the remoteness of the population location, areas that are difficult to access, being in protected areas or customary lands, and also due to continuous fishing by a catcher, accidents while climbing nest trees, and also awareness-raising activities carried out by various non-governmental organizations. However, hunting activities are still ongoing today and could lead the cockatoo population to extinction in the future if not stopped.
Rinca-Robong-Flores, cockatoo monitoring location
From July to September, Anna monitored the population of Citron-crested Cockatoo to get the latest population estimation. The monitoring was using the distance sampling technique to match the results of previous monitoring of cockatoo populations as closely as possible, including other key bird species, and habitat parameters. In October, Anna and Indonesia's Junior Bird Ecologist, Benny Aladin, will calculate the estimated cockatoo population in Komodo National Park. They will spend 4-6 weeks on the islands of Komodo and Rinca and use a distance sampling technique similar to that done on Sumba.
Looking for cockatoos on Adonara Island
The Citron-crested Cockatoo breeding season will begin when Anna and Benny return to Sumba. Camera traps will be installed at the nest site for a full year. They expect more active nest cavities and new nesting sites. When the breeding season ends, and the chicks starting to learn to fly, Anna will monitor the distribution of other cockatoo species in the current population locations: the islands of western Timor and Timor Leste, Sulawesi and the islands of Tanahjampea and Wakatobi.
The Cacatua sulphurea abbotti—another subspecies of Yellow-crested Cockatoo—in the remote Masalembo Island perhaps will not be visited considering its small population. Also, it's being intensely monitored by other organization. When the results of all this monitoring are gathered, they will gain a better understanding of the status of the Yellow-crested Cockatoo in order to identify important areas for long-term conservation action.
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[1] At the time of this writing, Anna and Junior Ecologist of Burung Indonesia, Benny Aladin, were monitoring the cockatoo population on Komodo Island.