Bali Starling Captive Breeding (Balen, 1990)

In October 1990, Bas van Balen and Harwono Gepak published a report 'Captive Breeding and Restocking into the Wild of the Bali Starling Leucopsar rothschildi' (available in pdf). Bali Starling numbers in the Bali Barat National Park, the only area where the species was known to occur, decreased sharply during the previous two decades due to habitat destruction and poaching.

Balen1990-balistarling-32Image right: cover (part)

A project aimed at the conservation of the species in the wild was initiated in 1987 by PHPA, ICBP, AAZPA and JWPT, in cooperation with Surabaya Zoo. This project seemed to be successful. Alas, figures 1 & 2 seem to be missing.


Bas van Balen (Bali Starling Project ICBP) & Harwono Gepak (Surabaya Zoological Gardens Captive Breeding Program)

NB. Secretariat The 3rd Conference of Zoos and The Meeting on the Establishment of Southeast Asian Zoos Association, Bogor, Indonesia, Proceedings: Jl. Harsono RM. No. 10, Ragunan, Pasar Minggu, Jakarta 12550 (P.O. Box 44 KBYL), Tel +62217800636, Fax. +62217802558


(p.23) Bali Starling numbers in the Bali Barat National Park, the only area where the species is presently known to occur, decreased sharply during the last two decades due to habitat destruction and poaching. A project aimed at the conservation of the species in the wild was initiated in 1987 by PHPA, ICBP, AAZPA and JWPT, in cooperation with Surabaya Zoo. Main objectives are a captive breeding program, the release of captive bred birds into the wild, monitoring of the wild population and public awareness programs. Until now, 17 captive bred birds came available and an attempt to release a group of 12 birds into the national park appears to have been successful.


There is serious concern about the Bali Starling's fate in the wild. Its numbers dropped in the last twenty years from several hundreds to a few dozen. The surviving population in Bali Barat National Park is still shrinking. The Indonesian Government (represented by the Directorate General of the Forest Protection and Nature Conservation), the International Council for Bird Preservation, the American Association of Zoological Parks and Aquaria, and the Jersey Wildlife Preservation Trust, initiated in 1987 a cooperative program to preserve this species in its native habitat on the island of Bali (Indonesia). Captive breeding and restocking into the wild are two objectives of the project, which at present has been running for almost three years, after a period of preparations, with a breeding stock housed in the Surabaya Zoological Park (E. Java).

Numerous programs throughout the world have been carried out with the ultimate goal to release birds into the wild for restocking/reintroduction of endangered species. Until now, all major attempts involved transfer and release of wild caught birds (e.g., Black Robin in New Zealand, Raven in (p.24) Netherlands). The few successful releases with captive bred birds involved non-passerine species. To date, the Bali Starling breeding program is the first large scale one aimed at saving a passerine species in the wild.

Breeding stock

In August-November of 1987 the already existing breeding facilities of the Surabaya Zoological Gardens, consisting of 29 aviaries and housing 16 Bali Starlings, were renovated. In November 1987, 4 3 birds, captive bred and donated by zoological gardens and private collections in the United State and United Kingdom arrived in the zoo (another seven birds died during transport and shortly after arrival).


Breeding cages for single pairs were at least 2.5 m high, 2.5m wide and 4 m deep. To avoid interaction with starlings in adjoining cages, screening the cages is being considered. Artificial nest boxes were provided following a design widely used in the U.S. (see Figure 1). Grass, leaves etc. were provided for nesting materials. In addition to dry food pellets, fresh local fruits (papaya, bananas) and live food (mealworms and ant pupae) were provided. Hand rearing of rejected hatchlings was considered undesirable because of unsuitability of the birds for future release.

Breeding results

Egg hatching rate during the first year was satisfactory. However, most chicks died within a short time after hatching and to date only 20 captive born birds came available for release. Breeding results during 1988-1990 are shown in Figure 2. A sharp increase in the number of clutches is clear in August, 1989, after the introduction of new nest boxes following the design widely used in the U.S., that induced many more birds to lay eggs. The death rate among the chicks remained disappointingly high. Moreover, none of the English birds laid eggs, even after the installation of new boxes.


Studbooks for the American and British captive populations already exist, and a regional studbook for Indonesia is being prepared. Other studbooks should be prepared for Central Europe (p.25) (where a captive breeding program is being set up) and for Bali Starlings in Japan and Singapore.

Minimal viable population

It is estimated that in order to preserve 90 percent of the average heterozygosity of the Bali Starling's gene pool in the (world) captive breeding stock, a population of 600 individuals is needed. The U.S. zoos and private collections together can only house some 400 birds, and therefore coordination is needed with European collections to increase the captive breeding population.

To date, the breeding stock in the Surabaya Zoo consists of 28 U.S., 3 British and 11 Surabaya birds, which are held separately. Only four pairs are successful breeders (pair 787 x 1082 disappeared in 1989). Recombination of the pairs, especially among the three different subgroups, is essential to enhance productivity of the Surabaya birds, and increase the effective breeding population.

The extension of the Indonesian propagation program to other sites on Java would also greatly increase the carrying capacity of the Indonesian captive population and the number of birds for the release program.

Release program

The building of a new Pre-release Training Center (PTC) in the Bali Barat National Park was completed in June 1988. The construction of the unit of 10 aviaries of each 5mx3mx2m followed the design of the Captive Propagation Center in the Surabaya Zoo. As its location the grounds of the Bali Barat Research Center at Tegal Bundar was chosen. The PTC is strictly closed to general public and sufficiently isolated to reduce any habituation of the birds to humans, including the keeper.

In July 1988 the first group of three birds from the Surabaya Zoo was accommodated in the PTC. To adjust the birds to their future environment, they received a training of six weeks during which not only foraging in the wild, and fear of humans was focused on, but the birds were gradually accustomed to the boxes in which they were to be transported to the spot of release. In the field, the birds would be released in turns during the first week, in order not to lose the birds too early from the site (the caged bird always attracted the released ones).

The attempt to introduce the first group of three birds (KBS 1-3) ended in one known casualty and disappearance of the (p.26) two other birds. The extremely dry conditions and strong wind at the time of release, the birds' unfamiliarity with the area, and the location of the site distant from any known Bali Starling roosting site may have caused the failure. In April 1988, eight captive breds (KBS 5-14; see Table 3) were brought over from the Surabaya breeding stock to Bali Barat National Park. Due to stress, one of the birds died shortly thereafter, and another bird lost one of its legs and became unfit for release. The birds were given various kinds of wild fruits, which are known to be eaten by Leucopsar. They readily took various arthropods, little reptiles, etc. that entered their cages. They showed fright reactions towards raptors flying over. In early 1990, two birds confiscated in E. Java were added to the group in PTC; one of these was considered for release, the other was assumed to be unfit for release, as its malformed bill suggested it had been hand-raised.

In April 1990 another six captive bred birds were transported from Surabaya Zoo to Bali Barat and housed in the PTC. The second attempt was planned for a location on the Prapat Agung peninsula in Bali Barat, where Bali Starlings were known to roost regularly. A two-compartment cage (2 x 2 x 2.5m) was built on the site to serve as a training accommodation. Birds unfit for release stayed in the cage to decoy released birds back to the release cage where food and water was provided during the first weeks. On the day the birds were transported to the release site, transponders were inserted and color rings applied. Special heavy duty rings, designed for the Bali Starling conservation program, were applied to the two confiscated birds. Breast feathers of the birds to be released were dyed red (rhoamine B) . On April 15, 1990 the first four birds were released from the cage where they had been housed during the previous two days. On April 17, three birds were released, followed by two, two, one and one on each consecutive day.

Daily monitoring of the starlings was done near the release site where during the first weeks food pellets, fruits and drinking water were provided. Reading of the ring codes soon became difficult, as the birds became increasingly wary. However, in early October, six months after the release, a marked bird was identified at a considerable distance from the release site.

Discussion (p.27)

Question (Linus Simanjuntak): 1. In your opinion, why is poaching of the Bali mynah still so prevalent? Is there a strong demand from collectors outside of Indonesia?; 2. About the white-wash campaign. What do you think can be done to make it effective?

Question (Erna Suzanna, DVM): During your experiment, have you found some diseases in Bali Starlings? If so, what are the clinical signs?

Question (Dewi M. Prawiradilaga): I am interested in the behavior of Bali Starlings. 1. Could you explain what kind of interactions happen between the wild birds and the captive birds released in the wild?; 2. How long did the captive birds take to adjust themselves to the wild environment.

Question (Richard Tenaza): You showed the decline in population but said nothing about habitat decline. Can you please comment on that.

Question (Linda Prasetyo): As you mentioned, Surabaya Zoo has received Bali Starling from AAZPA. But I've heard that all the chicks died. Do you have any idea about what the problem was and what is your suggestion to solve the problem?

Question (Dr. S. Thiruchelvam): 1. What's the incidence of Haemachromatosis in captive reared Bali mynahs? Is it diet related? (p.28); 2. Jurong Bird Park has a good breeding pair of Bali mynahs and would be glad to make their progeny available for the release program.

Question (Moh. Tajuddin Abdullah, Zoo Malaka): Are there any specific diseases related to your high chick mortality?

Question (Dr. Ratna Kumar): Can you kindly explain the reasons for chick mortality of Bali Starling. I wish to know whether post mortem studies have been conducted and any specific diseases identified.

Question (Tunku Nazim): 1. Do birds that have been bred over many generations
in different climatic zones show any selection for their non-natural areas?; 2. What is being done to protect the wild birds, both law enforcement and public education?; 3. Is this project a good use of scarce funds for species conservation?

Question (Boediardjo): 1. Are there similar cases like the Bali Starling which attract such world wide attention?; 2. How far are private bird breeders encouraged to participate in captive breeding of birds in general, and Bali Starlings in particular.

Question (D. Ashari): One of the aspects to support the Bali Mynah Captive Breeding Project is the collection of fresh genetic pools from the unregistered birds of individual owners in Indonesia. We have in mind a "white wash" campaign in which those unregistered birds will not be confiscated, but will be exchanged for captive-bred specimens. In this regard, the AAZPA will support the project by sending more captive-bred from U.S. Zoos.

(p. 29) Question (Idris Abd. Malik): Do you take the eggs for artificial incubation, or do you just leave them with the parents?


1. There is not much to add to Mr. Ashari's information about the objectives of the white wash campaign. It is hoped that things will happen soon, considering the age of the birds concerned. Most of the starlings possessed by private individuals were caught when the species was still relatively common in its natural habitat, i.e. years ago. At present an inventory is being made of the captive birds.

2. a. The Californian Condor, the Nene (or Hawaiian Goose) and Peregrine Falcon are some of the most famous examples. b. The private owners of Bali Starlings could be potential breeders. However, the coordination and administration of a large number of breeders could become very complicated, and we should therefore be very careful.

3. a. No special studies have been made on this matter. However, offspring of birds brought over from the United States were raised in Surabaya (with climatic conditions not very much differing from Bali), and appeared to do well in the wild, not showing genetically acquired unfitness; b. The very recent amendments of the old (Dutch) laws on nature conservation and environment will certainly change the situation as it existed until now, in which it was almost impossible to prosecute trespassers of the law adequately (no poacher or dealer of Bali Starling has ever been prosecuted). Visits to schools, introduction days, distribution of posters and publications in local newspapers and magazines are some of the activities of the Bali Starling Project in the last years. In the near future ICBP will start a special education program in Indonesia; c. The public attention the project receives, especially in Indonesia, and the expertise and knowledge obtained from the captive breeding and releasing into the wild justify the spending of money. The significant (however, temporary it (p.30) may have been) success booked with the release of the captive-bred birds, gives us hope for more success in the future.

4. Coccidiosis is a rare disease commonly found in harmless levels in adult birds, but can cause mortality in chicks. A coccidostat treatment was advised for the Surabaya birds. It seems, however, that most of the chicks in the Surabaya Zoo died because they were thrown out of their nests or injured while still in the nest. The parents inflicted this maltreatment on their own chicks.

5. a. Haemachromatosis has indeed been found in captive Bali Starlings, (as it has been in many other starling species and also Birds of Paradise) . As far as I know, it can be largely suppressed by iron-poor diets.

6. The eggs and hatchlings are left with the parents, and even in cases of rejected chicks hand-raising was taboo. This is in order to avoid any wrong imprinting which would make the birds unfit for release into the wild.

7. Post mortem studies of dead chicks did not reveal more than mentioned above.

8. The decline of natural habitat along a large part of the north coast of Bali Starlings may have caused the initial major decrease of Bali Starlings in the wild. Poaching aggravated the shrinking of the remaining numbers. Though not very much information on Bali Starling habitat in former days exists, the species may be rather non-selective as attested by reports of dozens of birds in teak forests and even along the borders of villages.

9. Stress of parent birds may be a major cause. The number of visitors in the Surabaya Zoo is normally very high, and isolating the breeding cages to avoid (visual) contact with humans was advised. The instalment of more disturbance-proof nest boxes resulted in more eggs being laid, but mortality of chicks remained high. The building of an entirely new aviary complex in a more remote place in the Zoo is being considered.

10. The captive-bred birds that were released did not take much time to adapt themselves. Most of them very soon joined wild flocks, and several pairs consisting of a released and a first-year wild bird were formed after a few days. During the first month water and food were provided, and the birds visiting the drinking/feeding spot were closely observed.

11. See above.

12. (p.31) a. Trading of Bali Starlings is still important because of the high prices paid for single birds (Rp. 600,000 and more). It makes poaching very tempting. The main reasons for collecting the species are its rareness (though many collectors don't even have an idea of how rare the bird actually is) and its protected status; b. Important in the white wash campaign are an accurate administration and strict leak-proof legal regulations (to avoid situations in which, for instance, dealers and poachers offer their freshly obtained birds for amnesty).


  • Balen, Bas van & Harwono Gepak (1990) – Captive Breeding and Restocking into the Wild of the Bali Starling Leusopsar rothschildi; The 3rd Conference of Zoos and The Meeting on the Establishment of Southeast Asian Zoos Association, Bogor, Indonesia, Proceedings, Oct. 22-25, 1990, p.23-31

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