Importance of seed dispersers like hornbills for the forest
Seed-dispersing species like hornbills and fruit bats feed on fruits of native species and distribute the seeds with their droppings. For very large fruits the Visayan Warty Pig is the most important seed disperser today. In ancient times, some of the now extinct megafauna (elephants, rhinos etc.) have played a crucial role in dispersing large fruits. Gut passage in addition to dispersal facilitates the germination of certain seeds. Fruit composition affects the duration of the gut passage. This way the plant can manipulate dispersers to achieve dropping of seeds in an optimum average distance from the tree, in places where they germinate best. This is because directly under the tree survival is reduced due to accumulation of natural enemies in the soil which harm the seedlings.
Seed-dispersing species are ecologically important helpers in rainforest regeneration and reforestation and therefore need to be protected. Large-fruited tree species may vanish if they lose “their” disperser species which they co-evolved with. PhilinCon protects such frugivorous species.
Janzen, D. H. & P. S. Martin (1982): Neotropical anachronisms: the fruits the gomphotheres ate. Science 215: 19-27.
Mangan, S. A., Schnitzer, S. A., Herre, E. A., Mack, K. M. L., Valencia, M. C., Sanchez, E. I. & J. D. Bever (2010): Negative plant–soil feedback predicts tree-species relative abundance in a tropical forest. Nature 466: 752-755. [PDF]
Protection of hornbills and their nests in the wild
In order to diminish losses by poaching and to increase the population size of seed dispersers, a variety of measures – besides anti poaching measures (“rice for rifles”) and alternative livelihood programs – have proven to be efficient.
Confiscated hornbills are treated by veterinarian Dr. Sanchez in our rescue facility. Juvenile birds are reared to adulthood. After rehabilitation and a final health check the birds are released back to the wild. Surveillance of nests of the large and particularly threatened Dulungan (Rhabdotorrhinus waldeni) by paid local people has proven to be extremely successful. The losses from poaching (brood and sometimes also females killed) dropped from 50% earlier to 5% since 2001.
Due to recent unjustified criticisms we have to stress that the goals of any conservation measures are the survival of the species, particularly when it is considered Critically Endangered. Nevertheless, the nest guarding program provides an environmentally sustainable income for local people and has increased the number of breeding pairs.
Enhancing the breeding success of endangered hornbills
Experience showed that after logging of too many old rainforest trees the remaining breeding pairs are competing for nest holes. Therefore, artificial hornbill nestboxes were developed and mounted. To slow rotting, the rather heavy nest boxes are made out of mahogany, a hardwood timber not native to the Philippines. By using wood of this locally grown alien tree species, regeneration of native hardwood tree species is indirectly supported.
One of the two hornbill species at stake has already nested several times in boxes thus hung up by PhilinCon.
Successful hornbill releaseS (1998 - 2005 - more birds have been released in the meantime)
A Visayan Tarictic male (Penelopides panini panini), confiscated as a fledgling and reared and trained by PanayCon staff, was gradually subjected to a ‘soft release’. It bonded up with a wild flock while gradually becoming independent of offered food. This was the first of any hornbill releases. Until early 2005, 22 Tarictic Hornbills could be successfully released, equipped with transmitters for monitoring the success. More Tarictics have been released since then. The experience from these releases helped to prepare the release of rehabilitated birds of an even more threatened species, the Writhed-billed Hornbill or Dulungan. Three Dulungans, one male and two females, were released in the NWPP in April 2015. Meanwhile, not only survival of most of the released hornbills but also successful breeding of Tarictics with wild mates can be reported. Furthermore, pair formation of released birds in the wild occurred soon upon release. Nest boxes were offered by PhilinCon in the forests around the station, and since 2002 are accepted by wild Tarictics for breeding.
The rehabilitation and release program was sponsored by Frankfurt Zoological Society, IDEXX, Chester Zoo, and the Mohamed Bin Zayed Species Conservation Fund, and still is by the Association for Bird Conservation and Aviculture (AZ) and the Bird Protection Committee.
Taken from: E. Curio (1998): The first ‘soft release’ of a juvenile Tarictic Hornbill (Penelopides panini panini). Publication No. 19 of the Philippine Endemic Species Conservation Project (PESCP) of the Frankfurt Zoological Society. Report compiled from records of Fel C. Cadiz, Benjamin ‘June’ Tacud, Henry Urbina and Eberhard Curio.
Lichtblicke für die Natur (2003): Newsletter, Stiftung bedrohte Tierwelt (Foundation for Endangered Wildlife). Frankfurt Zoological Society (German, authored by E. Curio: Highlights of Progress for Nature).
Recommended literature: Margoluis, R., Salafsky, N. & Balla, A. (Illustrator), 1998: Measures of success: Designing, managing, and monitoring conservation and development projects. Island Press. ISBN: 1559636122 (Paperback, 363 pages)