Great Hornbill Buceros Bicornis Research Articles

Distribution of Hornbills and Important Hornbill Landscapes - Setting Site Conservation Priorities for Peninsular Malaysia

Malaysia is an important hornbill range country in Asia supporting a total of 10 hornbill species. Malaysia ranks second (collectively with Myanmar and the Philippines) after Thailand and Indonesia (both 13 species respectively) in terms of hornbill diversity per country. Within Malaysia, all 10 species has been recorded in Peninsular Malaysia whereas Sabah and Sarawak have 8 species each. The Great Hornbill Buceros bicornis and Plain-pouched Hornbill Rhyticeros subruficollis do not occur in Borneo. Despite being iconic tropical forest birds, our understanding of its local distribution status, ecology and biology remains limited. In this paper, we conducted a broad examination of the hornbills’ distribution in Peninsular Malaysia based on more recent information gleaned mostly from grey literature e.g. birding trip reports, scientific expedition reports, department annual reports, selected Facebook birding group postings, proceedings, bird databases (MNS Bird-I-Witness) etc. Information from primary literature e.g. local/regional journals were also taken into account where available. The purpose of this exercise is two-fold, (1) to update our knowledge post-Wells (1999) about hornbill distributions in Peninsular Malaysia in light of continuing deforestation and habitat degradation and (2) identify Important Hornbill Landscapes (IHL) in need of protection and conservation to preserve viable hornbill populations.

Looking beyond parks: the conservation value of unprotected areas for hornbills in Arunachal Pradesh, Eastern Himalaya

AbstractThe loss of tropical forests and associated biodiversity is a global concern. Conservation efforts in tropical countries such as India have mostly focused on state-administered protected areas despite the existence of vast tracts of forest outside these areas. We studied hornbills (Bucerotidae), an ecologically important vertebrate group and a flagship for tropical forest conservation, to assess the importance of forests outside protected areas in Arunachal Pradesh, north-east India. We conducted a state-wide survey to record encounters with hornbills in seven protected areas, six state-managed reserved forests and six community-managed unclassed forests. We estimated the density of hornbills in one protected area, four reserved forests and two unclassed forests in eastern Arunachal Pradesh. The state-wide survey showed that the mean rate of encounter of rufous-necked hornbills Aceros nipalensis was four times higher in protected areas than in reserved forests and 22 times higher in protected areas than in unclassed forests. The mean rate of encounter of wreathed hornbills Rhyticeros undulatus was twice as high in protected areas as in reserved forests and eight times higher in protected areas than in unclassed forests. The densities of rufous-necked hornbill were higher inside protected areas, whereas the densities of great hornbill Buceros bicornis and wreathed hornbill were similar inside and outside protected areas. Key informant surveys revealed possible extirpation of some hornbill species at sites in two protected areas and three unclassed forests. These results highlight a paradoxical situation where individual populations of hornbills are being lost even in some legally protected habitat, whereas they continue to persist over most of the landscape. Better protection within protected areas and creative community-based conservation efforts elsewhere are necessary to maintain hornbill populations in this biodiversity-rich region.

The status and conservation of hornbills in Cambodia

Internal security problems from the 1960s up until 1998 prevented any fieldwork in Cambodia. Since then, the situation has improved greatly and the Royal Government of Cambodia, in collaboration with international conservation NGOs, has been conducting general biological surveys across the country. Survey reports were used to investigate current occurrence of hornbills. Historically, three hornbill species — Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus and Oriental Pied Hornbill Anthracoceros albirostris — were known from Cambodia. Recent surveys show that populations of Great and Wreathed Hornbills have declined significantly since the 1960s, while Oriental Pied is still common. A fourth hornbill species, Brown Hornbill Anorrhinus tickelli, was reported in 1998 in Kirirom National Park spanning the border of Koh Kong and Kompong Speu provinces in south-west Cambodia. Conservation priorities and priorities for future surveys are being developed.

Nest-site selection and nesting success of three hornbill species in Arunachal Pradesh, north-east India: Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus and Oriental Pied Hornbill Anthracoceros albirostris

Nest-site selection by the sympatric Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus and Oriental Pied Hornbill Anthracoceros albirostris was investigated in a lowland tropical forest in Arunachal Pradesh, north-east India during 1997–2000. Information on two nests of Rufous-necked Hornbill Aceros nipalensis in higher-elevation forests is also presented. All species nested in live trees of three tree genera, 83% (n = 36) in Tetrameles nudiflora, an emergent deciduous softwood, relatively common in lowland foothill forests. No difference was recorded in nest-tree species or nesting habitats of sympatric hornbills, but there were a few differences in structural characteristics of nest-trees. Cavity size was the main variable separating the three species. Great Hornbills used larger cavities while Oriental Pied Hornbills used smaller cavities closer to riverine areas. Nesting was attempted at 64% of known sites and successful fledging of chicks was 80% overall (n = 72 nests, pooled over 4 years). Nest-trees in disturbed habitats near human habitation were used but were often abandoned or unsuccessful and 50% of all nest-trees were inactive by the end of the study. Potential large nest-trees had a density of 5.9/ha, that of the two most used species was 1.3/ha, and minimum nest densities of all three species was about 1 pair/km2. Interference competition for nest-sites was not observed, despite similarity in nest-tree characteristics, low nest density and high loss of nest-trees. Nest-site availability may naturally limit hornbill populations in the area, and additional loss of nesting habitat to human activities may exacerbate limited availability of breeding sites.

Correlates of hornbill distribution and abundance in rainforest fragments in the southern Western Ghats, India

The distribution and abundance patterns of Malabar Grey Hornbill Ocyceros griseus and Great Hornbill Buceros bicornis were studied in one undisturbed and one heavily altered rainforest landscape in the southern Western Ghats, India. The Agasthyamalai hills (Kalakad-Mundanthurai Tiger Reserve, KMTR) contained over 400 km2 of continuous rainforest, whereas the Anamalai hills (now Indira Gandhi Wildlife Sanctuary, IGWS) contained fragments of rainforest in a matrix of tea and coffee plantations. A comparison of point-count and line transect census techniques for Malabar Grey Hornbill at one site indicated much higher density estimates in point-counts (118.4/km2) than in line transects (51.5/km2), probably due to cumulative count over time in the former technique. Although line transects appeared more suitable for long-term monitoring of hornbill populations, point-counts may be useful for large-scale surveys, especially where forests are fragmented and terrain is unsuitable for line transects. A standard fixed radius point-count method was used to sample different altitude zones (600–1,500 m) in the undisturbed site (342 point-counts) and fragments ranging in size from 0.5 to 2,500 ha in the Anamalais (389 point-counts). In the fragmented landscape, Malabar Grey Hornbill was found in higher altitudes than in KMTR, extending to nearly all the disturbed fragments at mid-elevations (1,000–1,200 m). Great Hornbill persisted in the fragmented landscape using all three large fragments (> 200 ha). It was also recorded in four of five medium-sized fragments (25–200 ha) and one of five small fragments (< 25 ha), which was adjacent to shade coffee plantations. Abundance of Malabar Grey Hornbill declined with altitude and increased with food-tree species richness. Great Hornbill abundance increased with food-tree species richness, suggesting that maintenance of high diversity of hornbill food species in fragments is important for their persistence. It is likely that the smaller and less specialized Malabar Grey Hornbill will survive in disturbed and fragmented forest landscapes, while Great Hornbill is more vulnerable to habitat alteration. Protection and restoration of rainforest fragments and food-tree resources, besides protection of existing large fragments, will aid the conservation of hornbills in the region.

Foraging Patterns of Sympatric Hornbills during the Nonbreeding Season in Arunachal Pradesh, Northeast India

ABSTRACTThe diet and food resource partitioning of three sympatric hornbills (Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus, and Oriental Pied Hornbill Anthracoceros albirostris) during the nonbreeding season were studied relative to fruit availability in a foothill semievergreen forest of Arunachal Pradesh, northeast India. Hornbills fed on fruits of 49 plant species that comprised over 95 percent of their diet. Hornbill species partitioned food resources by varying the relative contribution of figs and non‐fig fruits in the diet. Similarity in non‐fig fruit diet was low. Ten species contributed to over 90 percent of the non‐fig diet. The availability of non‐fig fruits was much lower in the nonbreeding season than in the breeding season; however, despite lower fruit availability during the nonbreeding season, hornbills had a wide diet breadth and indirect evidence suggests that Wreathed Hornbills foraged widely in this season for fruit. Great Hornbills relied more on figs that were available year‐round. The diverse diet breadth that included rare and patchy fruit resources underscores the importance of conserving large forest tracts for hornbills.

Foraging Patterns of Sympatric Hornbills during the Nonbreeding Season in Arunachal Pradesh, Northeast India1

The diet and food resource partitioning of three sympatric hornbills (Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus, and Oriental Pied Hornbill Anthracoceros albirostris) during the nonbreeding season were studied relative to fruit availability in a foothill semievergreen forest of Arunachal Pradesh, northeast India. Hornbills fed on fruits of 49 plant species that comprised over 95 percent of their diet. Hornbill species partitioned food resources by varying the relative contribution of figs and non-fig fruits in the diet. Similarity in non-fig fruit diet was low. Ten species contributed to over 90 percent of the non-fig diet. The availability of non-fig fruits was much lower in the nonbreeding season than in the breeding season; however, despite lower fruit availability during the nonbreeding season, hornbills had a wide diet breadth and indirect evidence suggests that Wreathed Hornbills foraged widely in this season for fruit. Great Hornbills relied more on figs that were available year-round. The diverse diet breadth that included rare and patchy fruit resources underscores the importance of conserving large forest tracts for hornbills.

Hornbill abundance in unlogged forest, selectively logged forest and a forest plantation in Arunachal Pradesh, India

The responses of hornbills to selective logging were determined by comparing their diversity and abundance in five habitats classified according to logging history. Relative abundance of three hornbill species was compared along trails in recently logged forest, 20–25-year-old logged forest, unlogged primary forest, a relatively disturbed primary forest and a plantation in Pakhui Wildlife Sanctuary and adjoining reserve forests in western Arunachal Pradesh. The species recorded were the Oriental pied hornbill Anthracoceros albirostris, wreathed hornbill Aceros undulatus and great hornbill Buceros bicornis. The great hornbill was the most common species overall and its abundance varied across habitats, being highest in unlogged forest. The Oriental pied hornbill, which was recorded in only two habitats, seemed to show a distinct habitat preference for secondary growth, rivermargin forests. Wreathed hornbill abundance did not differ between habitats. Differences in species abundance probably reflect aspects of their ecology, such as degree of territoriality, diet and movement patterns, and differential vulnerability to hunting and disturbance. Great hornbill abundance was correlated with large tree density (GBH ≥ 150 cm) and basal area characteristic of unlogged primary forests, while Oriental pied hornbill abundance was negatively correlated with tall forest, indicating its greater numbers in low-stature river-margin forest. Wreathed hornbill abundance was not correlated with any vegetation variable, which is probably related to its reported nomadic movements in search of fruit patches. Hornbill abundance was not correlated with densities of potential food and nest tree species. Although hornbill abundance was not correlated with fig tree density, this was probably because areas where relative fig tree densities were lower often contained a few large fruiting figs. Because hornbills are large mobile birds, they can find resources such as fruiting figs even in otherwise unsuitable habitat.

Hornbill abundance in unlogged forest, selectively logged forest and a forest plantation in Arunachal Pradesh, India

The responses of hornbills to selective logging were determined by comparing their diversity and abundance in five habitats classified according to logging history. Relative abundance of three hornbill species was compared along trails in recently logged forest, 20–25-year-old logged forest, unlogged primary forest, a relatively disturbed primary forest and a plantation in Pakhui Wildlife Sanctuary and adjoining reserve forests in western Arunachal Pradesh. The species recorded were the Oriental pied hornbill Anthracoceros albirostris, wreathed hornbill Aceros undulatus and great hornbill Buceros bicornis. The great hornbill was the most common species overall and its abundance varied across habitats, being highest in unlogged forest. The Oriental pied hornbill, which was recorded in only two habitats, seemed to show a distinct habitat preference for secondary growth, rivermargin forests. Wreathed hornbill abundance did not differ between habitats. Differences in species abundance probably reflect aspects of their ecology, such as degree of territoriality, diet and movement patterns, and differential vulnerability to hunting and disturbance. Great hornbill abundance was correlated with large tree density (GBH ≥ 150 cm) and basal area characteristic of unlogged primary forests, while Oriental pied hornbill abundance was negatively correlated with tall forest, indicating its greater numbers in low-stature river-margin forest. Wreathed hornbill abundance was not correlated with any vegetation variable, which is probably related to its reported nomadic movements in search of fruit patches. Hornbill abundance was not correlated with densities of potential food and nest tree species. Although hornbill abundance was not correlated with fig tree density, this was probably because areas where relative fig tree densities were lower often contained a few large fruiting figs. Because hornbills are large mobile birds, they can find resources such as fruiting figs even in otherwise unsuitable habitat.