Increasing breeding success in the critically endangered Bali starling (Leucopsar rothschildi) through new, improved husbandry techniques

Bali starlings (Leucopsar rothschildi) are one of the world’s rarest birds, found in just one forest, in the protected Bali Barat national park on Bali. In 2001, there were just six Bali starlings left in the wild due to habitat loss and poaching for the exotic songbird trade.

In-situ conservation efforts have raised this number to between 50 and 100, however, the captive breeding efforts of zoos are going to be essential to replenishing the numbers of Bali starlings in the wild. Bali starlings are notoriously difficult to breed in captive environments and traditionally, suffering from a lack of genetic diversity, environmental issues, and poor parenting. Therefore, hand-rearing has often become necessary to maintain breeding lines. This, however, can have a negative effect on the future parenting ability of the offspring, perpetuating the poor parenting behaviours of an already critically endangered species, thus making parent-reared chicks highly valuable.

In March 2020, Cleopatra, a female Bali starling, joined Battersea Park Children’s Zoo’s (BPCZ) male, Casper, and research into improving the breeding success of the species began. Early breeding efforts resulted in the same issues faced by other zoos, particularly iron storage disease and poor parenting. It was noted that dietary changes did not have an impact on reducing iron storage problems in chicks, thus research was carried out by Jamie Baker and Lizzy Humphries to find an alternative cause. Research noted a possible link between immunological stress, such as coccidian infections, and haemochromatosis. It is speculated that when infected with bacteria, birds, like mammals, may sequester free iron into the liver temporarily to prevent the bacteria entering the cycle of reproduction. This may be why birds who die of atoxoplasmosis appear to have an enlarged liver - the cause of death being hemochromatosis, triggered by a coccidian infection.

Upon this discovery, Jamie and Lizzy implemented a new husbandry routine for the birds, aiming to reduce the chances of immunological stress. This included a new cleaning routine, as well as giving every bird a drop of baycox every month. Parenting behaviour has also improved through research and changes in enclosure design, enrichment and feeding patterns. Following this husbandry change, combined with maintaining a low iron diet, Cleo and Casper have reared more birds over the last twelve months than any other zoo in Europe, the USA or participating zoos in Asia or Oceania, except for Prague Zoo, who also reared eight.

This success was the culmination of research which has taken place over the previous three years, in collaboration with the Begawan Foundation in Bali, who work to rear and release captive Bali starlings into the wild. BPCZ’s research has led to the creation of a new Bali starling care sheet, which will enable other collections to improve both the breeding success of their Bali starlings as well as their overall captive welfare.

This projected was submitted to the BIAZA Awards Animal Husbandry, Care and Breeding category 2023 and won a Gold award.