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 ForestFocus on Indonesia: Page 5 Hornbills also spread the seeds of other plants. In India, Great Pied Hornbills are vital to the dispersal of nutmeg seeds, since they are the only species with a beak large enough to open the seeds (Youth 1995). Ragupathy Kannan, a biologist studying this species in the Ghats region of southwestern India, discovered that the forestry department was intentionally cutting large fig trees in order to feed domestic Asian Elephants to haul lumber (Youth 1995). Kannan managed to convince them to ban fig tree cutting and, instead, to let Elephants browse freely in the forest (Youth 1995). If such conservation work took place throughout the ranges of hornbills, their future might be brighter.
The decline of hornbills throughout their Asian ranges highlights the loss of seed dispersers, as the forests themselves disappear or become logged over and fragmented. Hornbills are extraordinary birds, with their enormous beaks composed of horn-like material and, often, colorful facial markings. Some have a casque on top of the bill, giving the appearance of a double beak. The Rhinoceros Hornbill (Buceros rhinoceros), for example, has a typical downward-curving, white pointed beak, but atop it a bright orange-red casque curls upward at the tip like a rhinoceros horn. This species, native to Malaysia, Sumatra, Borneo and Java, has declined from trade and is listed on Appendix II of CITES. Averaging more than 4 feet long with 3-foot tails, hornbills make dramatic silhouettes as they fly over the forest canopy. Unfortunately, their size attracts hunters who kill them for sport or food, another factor in their rarity outside national parks. Their reproduction is highly unusual--unique, in fact--among birds. Courtship can involve spectacular head‑on collisions between males, clashing their casques together. The hornbill pair, which mates for life, selects a nest hole high in a hollow tree, usually one that was created by a large limb falling off and the trunk area becoming rotted.
Since ideal nest sites are rare and found only in trees hundreds of years old, hornbills often use the same nest year after year. The female plasters the inside with droppings that harden, and the male plasters the outside, leaving a slit that effectively imprisons the female in the tree trunk hole for the next three months. She pokes her bill out to receive food from the male, who tips his beak into the female's open one and lets small round figs and other grape-sized fruits roll down. Other adults may help in feeding the chicks and female. Before the chicks are ready to fledge, the female breaks out and leaves the nest; the chick or chicks instinctively reseal themselves for another month, both parents continuing to feed them (Yates 1992). Finally, when ready, the chicks break out of the nest. It is thought that hornbills have evolved this method of reproduction to protect the female and young from tree‑climbing predators, such as snakes and lizards. (The courtship behavior, nesting and feeding of the female and chick by the male Red-billed or Celebes Hornbill (Penelopides exarhatus) are beautifully photographed in the BBC film, “Castaways of Sulawesi.” See Video section.)
Hornbills, so important to fig trees and the host of species that feed on them, are themselves dependent on primary rainforest (Collins 1990). Their nest trees are often intentionally cut to obtain chicks for sale to zoos and in open wildlife markets. When these great trees crash down, they bring with them many adjoining trees, killing small mammals and birds in the process. The dual threats to hornbills of habitat loss and capture have resulted in dramatic declines in their populations. Should all the hornbill species that are threatened become extinct, the extinction of hundreds of other species may result, from the fig trees, whose seeds they spread, to many vertebrates and invertebrates. In 1980, only one species, the east Asian Helmeted Hornbill (Buceros vigil), was listed as Indeterminate by the International Council for Bird Preservation (ICBP) (now BirdLife International) as a result of killing to use their large casques for carving (King 1980). But by 1988, that organization listed seven Asian hornbills as threatened with extinction (Collar and Andrew 1988). In 2000, 18 of Asia's 30 species, or 60 percent, of hornbills were listed in Threatened Birds of the World (BI 2000). Seven of the 10 Philippine endemic hornbill species are threatened with extinction (BI 2000). The dramatic increase in threat to these keystone rainforest birds is a reflection of the destruction of Asia's rainforests.
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