Figs and hornbills
WHAT would bring back hornbills and other birds? Why have they disappeared? Why are figs important?
Food. Hornbills in general are fruit eaters and these iconic and culturally significant birds have a passion for figs. Figs (Ficus) are members of the mulberry (Moraceae) family. Of the over 160 species found in Borneo, 25 have been documented as key food sources not only for birds, but also monkeys (gibbons), bats, squirrels, sun bears and bearded pigs.
These ‘keystone species’ (species on which whole ecosystems depend) produce fruit year round and can support entire ecosystems. This fruit production strategy is the opposite of that of many other tropical species, including Dipterocarps, which fruit simultaneously (mast fruiting). This ensures that some seeds survive predation by birds, mammals and insects.
Figs, ancient plants with about 800 species worldwide, are mainly found in the tropics. All are fast growing softwood trees or shrubs. In Sarawak, figs fall into three broad groups.
The most dramatic are the strangling figs. The seeds of these upper-storey species are dropped into the canopy of a host tree. If they land in spot that can support growth and has moisture, the seed will sprout. The strangling fig sends down a support branch, then long rope-like roots extend to the ground, and these eventually completely enclose the host tree. Over time, as both grow and exert pressure, the stronger fig roots dominate and kill the host.
Figs can also be free standing trees, and these are often found along rivers. They produce fruit on bare twigs or stems.
The third group is the earth figs that fruit are on runners partly buried in the soil. Most figs are either found in the high canopy or on low bushes.
In recognition of the importance of figs in the natural ecosystems the Sarawak Forestry Corporation (SFC) has established the first 7.2ha Fig Garden in a degraded patch of forest in Matang Wildlife Centre, which is part of Kubah National Park. This park is approximately one hour from Kuching.
During the opening of Sarawak’s first Fig Garden last May, Ministry of Resource Planning and Environment permanent secretary Datu Sudarsono Osman said it was established as part of the Western Sarawak Hornbill Project, which aims to conserve the range and habitat of these birds. This project encompasses 306,000 ha and has incorporated national parks, including Kubah, nature reserves and wildlife sanctuaries located in western Sarawak.
Sudarsono noted that the Western Sarawak Hornbill Project is one of several initiatives of the state government to protect and conserve the environment, including habitat enrichment.
SFC deputy chief executive officer Oswald Braken Tisen said that although hornbills are the targeted species, all birds would reap the benefits associated with the enhancement and rehabilitation of this forest plot.
Figs, as mentioned, are important sources of food, but birds need shelter and nesting sites. Three hundred saplings, including six species of figs, and eight other indigenous forest tree species Jambu Laut (Eugenia sp), Ubah (Eugenia sp), Kubal (Willughbeia sp), Dabai (Canarium odontophyllum), two species of Bintangor (Calophyllum), Selangan Batu (Shorea sp,) and Engkabang Melapi (Shorea macrobalanos), were planted during the opening of the garden.
This 2,230ha national park is home to over 150 species of birds, including the White-crowned Hornbill (Berenicornis comatus), a rare bird that prefers dense shrubby vegetation next to rivers.
Sarawak, although frequently referred to as the ‘Land of the Hornbills’, has only eight of Malaysia’s nine species (there are 45 worldwide). These include the Oriental Pied Hornbill (Anthracoceros albirostris), which has come to prominence as it can adapt to city environments and a pair has raised chicks in the urban Piasau Nature Reserve in Miri. Oriental Pied Hornbills are common in coastal and secondary forests. The Rhinoceros Hornbill (Buceros rhinoceros), Sarawak’s state bird, is also widely recognised.
The other species of hornbills are the Bushy-crested Hornbill (Anorrhinus galeritus), Wreathed Hornbill (Rhyticeros undulatus), Wrinkled Hornbill (Aceros corrugatus), Helmeted Hornbill (Rhinoplax vigil) and Asian Black Hornbill (Anthracoceros malayanus). The presence of these iconic birds, which everyone wants to see, indicates that the general ecological health of a forest is good and that it provides food, shelter and nesting sites.
As mentioned, figs provide food for many species of birds, including the iconic hornbill as well as mammals. In turn the animals spread the tiny seeds, which either pass through their digestive tracts unharmed or better able to germinate, far and wide. Figs and animals benefit in this complicated web that becomes even more intricate when seed and fruit production are considered.
Seed dispersal is but part of the story and the webs that encircle figs. Fig species and the tiny fig wasps from the Agraonidae family have coevolved since the time of the dinosaurs, approximately 65 million years ago, with mutually dependent life cycles of approximately the same length. The fig wasps pollinate the figs, which in return provide a safe environment for the wasps to reproduce.
A green bottled-shaped fig looks like a regular fruit but is a pseudo or false fruit, called a syconium. Each encloses hundreds or thousands of flowers, that, if pollinated produce seeds. The flowers of the different fig species are structurally quite variable and this has led to one or two species of fig wasps adapting to pollinate a single species of fig.
The cycle starts when a tiny two-millimetre long female wasp enters a mature syconium through an equally small opening at the apex called an ostiole. The wasp has been attracted by the scent of the flowers.
Once a female wasp enters a syconium it cannot leave as its wings have been scraped off while squeezing in. Several female wasps can enter a single syconium and a clump of wings can be seen at the entrance. The female wasp lives for one or two more days after laying her eggs and pollinating the flowers.
At this point you might ask do we eat wasps when we eat figs. No, the crunchiness in figs is seeds from the hundreds or thousands of flowers, not wasps. The fig excretes an enzyme that enables the fig to absorb the wasp.
The sightless and wingless males, which spend their entire lives within the syconium, have two functions. The first is to mate with the females and the second is to bite a hole through the syconium to enable the female wasps to escape and find another fig syconium to enter, pollinate and deposit eggs.
About 34 million years ago, some figs evolved to produce a syconium with either male or female flowers and to be dioecious (to have male flowers and female flowers on separate plants). This was a point of evolutionary conflict since the fig was less cooperative with the wasp. The female flowers emit a scent that is similar to the male flowers, to entice the female wasp. This is a dead end for the wasp, because the flowers have evolved so that wasps cannot lay eggs. However, the fig gets pollen and then can produce seeds. If the female wasp enters a male flower, it can lay its eggs and form gall flowers, resulting in the continuation of the fig’s lifecycle.
The fig fruiting cycle and the fig wasp life cycle are approximately two months, leading to year round availability of fruit. This is why figs are called keystone species. All fig species are protected under Sarawak’s Wildlife Protection Ordinance 1998 because of their importance as a food source.
The interdependency of figs, frugivores (animals that eat fruit) and fig wasps demonstrates how complicated natural ecosystems are. However, this becomes even more so when the intricately interwoven webs of life of other creatures are also considered. Take for example nematodes or parasites that prey on wasps; consider the epiphytes that are attached to the boles of trees, including figs, and the micro ecosystems contained within one; or the predators (including hunters) that prey upon the birds and animals that consume the fruit.
In my view this illustrates a natural tapestry. If one component is removed, then other threads begin to unravel. What are the consequences if the seed dispersers, for example hornbills, disappear or become fewer? What are the consequences if the figs become less common?