The Writhe-billed Hornbill (Aceros waldeni) and the Visayan Tarictic Hornbill (Penelopides p. panini) are among the most threatened bird species of the Philippines. Both are known from just a few islands of this Pacific state. The Tarictic Hornbill is rare on Negros and Panay, on the latter island with a few hundred pairs restricted to the western mountains. On Guimaras, located between both islands, the species is extinct due to conversion of native forest into mango plantations. According to IUCN the Writhe-billed Hornbill is actually critically endangered, with some 100 pairs on Panay. Both species are confined to primary rainforests and breed in the cavities of old giant trees. Since they are unable to create such holes by themselves, both species likely suffer from an acute lack of nesting opportunities in view of the fact that old hardwood trees are removed by illegal organized timber cutting. Moreover, nestlings are still being removed and sold on local markets as pets.

Under the supervision of Prof. E. Curio, Ruhr University Bochum (Germany), the “Philippine Endemic Species Conservation Project” (PESCP) has been carrying out species conservation projects and related primary forest field studies since 1992, based on a contract with the Department of Environment and Natural Resources of the Philippines Government. Several measures aimed at the conservation of both two hornbill species and their forest home, and also for the protection of the interests of local inhabitants, were started in order to increase the relict populations of these two hornbills. This includes information campaigns (“No drinking water without forest”, “No forest rejuvenation without birds”) and measures to improve local people’s income. Moreover, a nest observation program was able to reduce the robbing of Writhe-billed Hornbill nesting cavities for the black market from 50 to ca. 5%.

An essential part of the PESCP rehabilitation program and survey is the release of hornbills originating from confiscations or donations of illegally kept individuals. They are tracked by using telemetry equipment purchased in 2005 with the help of the Brehm Fund. Firstly the Visayan Tarictic Hornbills were nursed to health or, in the case of young birds, fed until they developed and molted fully in captivity. The birds were also trained using fruit-loaded twigs to improve their locomotion skills in branches. Prior to release they were carefully checked by the veterinary surgeon on the project, who had improved methods of pathogen detection (e.g., NCD, Chlamydia, parasites) and the most modern blood analyzer available (VetTest 8000) at his disposal. Subsequently they were carefully liberated (“soft-release method”) into the forest around the research station, located on a peninsula in northwest Panay.

Hornbill individuals intended for release are marked by banding and equipped with miniature radio transmitters to follow their fates. After being released the birds are tracked via receivers and Yagi antennae for as long as possible. Altogether 14 of 18 released individuals were tracked over periods of 7 to 125 days, and their food intake, roosting sites, mortality due to predation (three cases), and first breeding in the wild all recorded. Two released males raised young with wild females, showing that the hand-raising and rehabilitation program had left their successful socialization unaffected. The short tracking times of single individuals suggested that they were no longer within reach of the antennae rather than that they had been predated. Therefore a system of long-range dipole antennae was installed in the tree canopy of the peninsula. Additional receivers and signal collectors will allow the tracking of any number of hornbills over long distances. Based on the relevant release experiences with the Visayan Tarictic Hornbills, at the beginning of 2006 the project scientists will start to release the first of the even more threatened Writhe-billed Hornbills in the same manner and with the same aim: building up a stable and self-sustaining hornbill population.

   Tracking of hornbills in the rainforest (© PESCP)

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