With land use change rapidly increasing in Asia, conservation prioritisation has emerged as an important tool in identifying critical landscapes for biodiversity to safeguard them from human pressures. In Peninsular Malaysia, the Malaysian Nature Society (MNS/BirdLife in Malaysia) developed a set of Criteria to identify Important Hornbill Landscapes (IHLs)-hornbill hotspots which are conservation priority sites in Malaysia and serve to inform land use planning and conservation action. Application of the Criteria has so far been restricted to Peninsular Malaysia, thus in this study, we adapt it to Sarawak, a Malaysian state in Borneo that supports 80% of the hornbill species diversity in the country. We expand on this conservation prioritisation methodology using Maximum Entropy Species Distribution Modelling (MaxEnt), to validate the Cri-teria's applicability and to identify potential IHLs in Sarawak. Our data sources included literature reviews, citizen science databases and interviews. Expectedly, survey effort was spatially biased. We identified eight IHLs, mostly concentrated in eastern Sarawak, across national parks, wildlife sanctuaries and forest management units. Existing published literature on the distribution of hornbill habitats in Sarawak corroborated with our MaxEnt outputs which aligned with the results of the IHL Criteria-based assessment, validating the latter and supporting its use in Sarawak. We additionally identified six potential IHLs based on MaxEnt outputs which confirmed the value of pairing MaxEnt with the Criteria-based assessment, for such a prioriti-sation exercise. To our knowledge, this study not only demonstrates the significance of combining MaxEnt and the Criteria for IHL identification, but it also represents the first application of the IHL Criteria outside of Peninsular Malaysia. Our findings can, therefore, serve as a case study for future applications of IHL Criteria in Borneo and potentially for other parts of Asia.
As interest in restoring tropical forests surges, so does the need for effective methods to ensure success. The framework species method (FSM) restores forest ecosystems by densely planting open sites, close to natural forest, with woody species, indigenous to the reference ecosystem and selected for their ability to accelerate ecological succession. Criteria for selecting framework species include: (i) representative of the reference forest ecosystem, (ii) tolerant of open conditions, (iii) ability to suppress weeds, (iv) attractiveness to seed-dispersing animals and (v) easily propagated. The method is effective where forest remnants and viable populations of seed dispersers remain. The origins and elements of the FSM are discussed. We review its adoption in 12 countries. Adherence to original principles was mostly high, but some misuse of the term was evident. The need for clearer definitions was identified. We place the FSM on a scale of restoration methods, matched with degradation levels and compare its establishment costs with those of other methods. Obstacles to its wider adoption, both technical and socio-economic, are discussed, along with how these might be overcome. Finally, the FSM is more clearly defined to facilitate its use in contributing towards the goals of the UN Decade on Restoration.
This article is part of the theme issue ‘Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration’.
We examined roost selection by hornbills using telemetry data and determined its implication for seed dispersal. Roost selection was not influenced by nest/foraging sites. Wreathed Hornbill roosts were mostly close to the river. Hornbills dispersed only 10% of seeds at roosts, but dispersal distances of those seeds were longer. We examined roost selection by hornbills using telemetry data and determined its implication for seed dispersal. Roost selection was not influenced by nest/foraging sites. Wreathed Hornbill roosts were mostly close to the river. Hornbills dispersed only 10% of seeds at roosts, but dispersal distances of those seeds were longer.
Seed dispersal by frugivores is vital to the maintenance of tree diversity in tropical forests. However, determining the influence of different frugivores over the distribution of their food plants is difficult, given the complexity of these interactions in the tropics. Consequently, most studies have been restricted to small scales, examining seed dispersal and establishment associated with nests, roosts or fruiting trees. Here, we evaluate the role of frugivorous hornbills in dispersing seeds at spatial scales of 1 ha. We monitored hornbills and seed rain at a tropical forest site in northeast India. We quantified the abundance of hornbill food plants and recruits of large-seeded plants. We estimated removal rates of dispersed, large seeds to determine post-dispersal seed fate. We found that the distribution of large-seeded canopy food plants influenced the distribution of the relatively abundant Rhyticeros undulatus. The overall distribution of hornbills resulted in spatially contagious seed rain patterns for the large-seeded plant species. Patches with canopy food plants had a higher recruit diversity. Our results show positive feedback between distribution of rare but important hornbill food plants, hornbills and distribution of seeds and saplings of large-seeded plants in the landscape. Widespread loss of hornbills due to hunting and habitat loss in the region have likely disrupted these feedback mechanisms that are critical for tree species regeneration.
Asian hornbills are known to forage and breed in fragmented rainforests and agroforestry plantations in human‐modified landscapes adjoining contiguous protected forests. However, the factors influencing year‐round hornbill abundance, demography and tracking of key food resources such as wild fig Ficus fruits in modified habitats and protected forests remain poorly understood. We carried out monthly surveys of two species of high conservation concern, the Vulnerable Great Hornbill (GH, Buceros bicornis) and the endemic Malabar Grey Hornbill (MGH, Ocyceros griseus) for 15 months and monitored ripe fig fruit availability for 12 months along 11 line transects (total length 24 km) in shade‐coffee plantations and adjoining continuous rainforests in a protected area (PA) in the Anamalai Hills, Western Ghats, India. Both hornbill species used plantations and the PA year‐round but distance sampling density estimates were higher in the PA in both nesting (GH by 57%; MGH by 50%) and non‐nesting (GH by 53%; MGH by 144%) seasons. Relative to estimates from 2004 to 2005, mean GH density appeared stable or increasing, whereas MGH had declined by 39% in the PA and by 56% in plantations. Monthly encounter rate of both hornbills tended to be higher in the PA and that of MGH was also positively related to the density of fig trees with ripe fruit. Sex ratios of observed adult birds in the non‐nesting season were relatively even (GH) or slightly female‐biased (MGH), but became male‐biased in both species during the nesting season when females were confined in tree‐cavity nests. We used change in the adult sex ratio of observed birds from the non‐nesting to nesting season to estimate an index of the proportion of adult pairs breeding at any point within the season, providing the first such estimates for any hornbill species. The proportion of breeding pairs was higher in the PA (GH – 56%, MGH – 64%) than in the plantations (GH – 33%, MGH – 30%). Although hornbills use shade‐coffee plantations year‐round, partly due to fig fruit availability, differences in hornbill density and breeding incidence, as assessed from the sex ratios of observed adult birds, indicate that plantations are a sub‐optimal habitat for both species.
Establishing protected areas (PAs) is an essential strategy to reduce biodiversity loss. However, many PAs do not provide adequate protection due to poor funding, inadequate staffing and equipment, and ineffective management. As part of China's recent economic growth, the Chinese government has significantly increased investment in nature reserves over the past 20 years, providing a unique opportunity to evaluate whether PAs can protect threatened species effectively. We compiled data from published literature on populations of gibbons (Hylobatidae), a threatened taxon with cultural significance, that occurred in Chinese reserves after 1980. We evaluated the ability of these PAs to maintain gibbon habitat and populations by comparing forest cover and human disturbance between reserves and their surrounding areas and modeling the impact of reserve characteristics on gibbon population trends. We also assessed the perspective of reserve staff concerning PA management effectiveness through an online survey. Reserves effectively protected gibbon habitat by reducing forest loss and human disturbance; however, half the reserves lost their gibbon populations since being established. Gibbons were more likely to survive in reserves established more recently, at higher elevation, with less forest loss and lower human impact, and that have been relatively well studied. A larger initial population size in the 1980s was positively associated with gibbon persistence. Although staff of all reserves reported increased investment and improved management over the past 20–30 years, no relationship was found between management effectiveness and gibbon population trends. We suggest early and emphatic intervention is critical to stop population decline and prevent extinction.
Estimating the abundance and spatial distribution of animal and plant populations is essential for conservation and management. We introduce the R package Distance that implements distance sampling methods to estimate abundance. We describe how users can obtain estimates of abundance (and density) using the package as well documenting the links it provides with other more specialized R packages. We also demonstrate how Distance provides a migration pathway from previous software, thereby allowing us to deliver cutting-edge methods to the users more quickly.
Responses of hornbills and Ducula pigeons to hunting and disturbances to their habitats may help us understand the implications for the regeneration of their dependent tropical forest trees. Moreover, density estimates serve as a gauge of whether some frugivorous birds can potentially substitute for the decline of their functionally-similar competitors. We carried out a year long survey of 24 line-transects distributed across disturbed (2 sites) and undisturbed (4 sites) habitats in the lowland evergreen forests of Pakke wildlife sanctuary and surrounding forests of Arunachal Pradesh. Hornbill and Ducula densities were estimated with DISTANCE. While densities of the Great Indian Hornbill, Buceros bicornis; Oriental Pied Hornbill, Anthracoceros albirostris, and wreathed hornbill, Aceros undulatus were substantially reduced in disturbed habitats, densities of the mountain imperial pigeon, Ducula badia and the green imperial pigeon, Ducula aenea were unaffected. These results suggest that Ducula pigeons may potentially provide substitute dispersal services for large-seeded tree species in disturbed sites, but that this response is most likely context driven.
Inferences based on counts adjusted for detectability represent a marked improvement over unadjusted counts, which provide no information about true population density and rely on untestable and unrealistic assumptions about constant detectability for inferring differences in density over time or space. Distance sampling is a widely used method to estimate detectability and therefore density. In the standard method, we model the probability of detecting a bird as a function of distance alone. Here, we describe methods that allow us to model probability of detection as a function of additional covariates—an approach available in DISTANCE, version 5.0 (Thomas et al. 2005) but still not widely applied. The main use of these methods is to increase the reliability of density estimates made on subsets of the whole data (e.g., estimates for different habitats, treatments, periods, or species), to increase precision of density estimates or to allow inferences about the covariates themselves. We present a case study of the use of multiple covariates in an analysis of a point-transect survey of Hawaii Amakihi (Hemignathus virens).
Amélioration des estimations de densité d’oiseaux par l’utilisation de l’échantillonnage par la distance avec covariables multiples
Ficus species are keystone plants in tropical rainforests, and hemi-epiphytic figs play a notably important role in forest ecosystems. Because hemi-epiphytic figs have strict germination requirements, germination and establishment stages regulate their populations. Despite the ecological importance of hemi-epiphytic figs in the rainforests, seed dispersal systems by fig-eating animals under natural conditions remain unknown because of the difficulty in tracing the destiny of dispersed seeds in the canopy. Therefore, seed dispersal effectiveness (SDE) has never been evaluated for hemi-epiphytic figs. We evaluated the SDE of hemi-epiphytic figs using qualitative and quantitative components by three relatively large-sized (> 3 kg) arboreal and volant animals in Bornean rainforests that largely depend on fig fruits in their diets: binturongs Arctictis binturong, Mueller’s gibbons Hylobates muelleri, and helmeted hornbills Rhinoplax vigil. The SDE values of binturongs was by far the highest among the three study animals. Meanwhile, successful seed dispersal of hemi-epiphytic figs by gibbons and helmeted hornbills is aleatory and rare. Given that seed deposition determines the fate of hemi-epiphytic figs, the defecatory habits of binturongs, depositing feces on specific microsites in the canopy, is the most reliable dispersal method, compared to scattering feces from the air or upper canopy. We showed that reliable directed dispersal of hemi-epiphytic figs occurs in high and uneven canopy of Bornean rainforests. This type of dispersal is limited to specific animal species, and therefore it may become one of the main factors regulating low-success hemi-epiphytic fig recruitment in Bornean rainforests.
Estimating the abundance and spatial distribution of animal and plant populations is essential for conservation and management. We introduce the R package Distance that implements distance sampling methods to estimate abundance. We describe how users can obtain estimates of abundance (and density) using the package as well as documenting the links it provides with other more specialized R packages. We also demonstrate how Distance provides a migration pathway from previous software, thereby allowing us to deliver cutting-edge methods to the users more quickly.
While large avian frugivores are known to be key dispersers for large‐seeded tree species, their role in community‐wide plant‐disperser networks is still poorly known. Large avian frugivores are also among the most threatened due to anthropogenic impacts.
We evaluated the role of large avian frugivores in a plant‐disperser community by (a) determining whether the plant‐disperser community was modular, with a distinct community of large frugivores (thereby highlighting their importance), (b) determining relative qualitative and quantitative roles played by large‐bodied frugivores vis‐à‐vis other frugivores and (c) determining impacts of large‐bodied frugivore loss on the plant‐disperser community.
The study was carried out at a tropical forest site in north‐east India, which is part of the Eastern Himalaya Biodiversity Hotspot. We collected tree watch data (20:55 hr) from 46 tree species, which represented 85% of tree species that are predominantly bird‐dispersed in the area.
We found that the plant‐disperser community was modular, with a distinct module of large‐seeded tree species and large frugivores. Intermediate‐sized frugivores such as barbets and bulbuls were the most connected, while large‐sized frugivores, such as hornbills and imperial pigeons, were moderately well connected. Qualitative and quantitative roles played by different dispersers varied across the gradient of frugivore body size. Hornbills, the largest avian frugivores, consumed a significantly greater number of fruits and swallowed larger proportions of fruits compared with other avian groups. In comparison with similar‐sized frugivores, imperial pigeons fed on larger‐sized fruits, highlighting their importance for dispersal of large‐seeded plants. Under simulated extinction scenarios, larger extinction cascades were not necessarily caused by larger frugivores; however, extinctions of certain large‐bodied frugivores (hornbills, imperial pigeons) caused extinction cascades.
Integrating information from networks and seed dispersal effectiveness approaches enabled a better understanding of large frugivore role in a plant‐disperser community. While large‐bodied frugivores may not be playing a central role in plant‐disperser communities, they are crucial as seed dispersal service providers for large‐seeded plants. In conjunction with the reported local extinctions of large frugivores like hornbills from the south Asian region, this study’s findings highlight the irreplaceable quantitative and qualitative impacts that tropical plant communities are likely to experience in the future.
Siamang (Symphalangus syndactylus) and agile gibbon (Hylobates agilis) were censused and mapped in Bala Forest, part of the Hala-Bala Wildlife Sanctuary, Narathiwat Province, South Thailand. Nineteen groups of siamangs and 136 groups of agile gibbons were found in this 168-km² area. This is the northernmost population of the siamang in Asia. Densities of siamangs were positively related to altitude, which reaches a maximum of 953 m in Bala Forest. In comparison with agile gibbons, siamangs occurred at higher altitude, lower-slope terrain, shorter distances from ridge-tops, and on more east-facing terrain. Both species occurred mostly in areas far from villages and the forest edge. Diminished submontane forest in Thailand, as well as competition with agile gibbons, may be limiting the distribution of siamang at the northern end of its range.
In Thailand, as for most of South-East Asia, large vertebrates are declining rapidly due to habitat degradation and increasing hunting pressure. Once relatively common in the evergreen forest of Southern Thailand, the Great Argus Argusianus argus is currently limited to a few populations, whose status is currently unknown. In this study we investigated changes in Great Argus abundance over the past 13 years in Hala-Bala Wildlife Sanctuary. Our aim was to estimate and compare the abundance and density of this species from an earlier two-year survey in 2001–2002 and ours in 2014, and to assess the effect of landscape change on its status of the species. We conducted surveys from March to August 2014 during the breeding season. We placed point counts that overlapped the line transects from the 2001–2002 survey. The results indicated a decline of > 35% in mean abundance from 2001 to 2014. In addition, male abundance has shifted and is now positively related to distance from the forest edge. High levels of human disturbance close to the forest edge may have resulted in the birds moving to the core of the forest, suggesting a need to increase protection and management of forest edge areas. In common with other studies of large vertebrates, our results confirm the importance of long-term studies to highlight the negative effects of human disturbance.
Ensuring that protected areas (PAs) maintain the biodiversity within their boundaries is fundamental in achieving global conservation goals. Despite this objective, wildlife abundance changes in PAs are patchily documented and poorly understood. Here, we use linear mixed effect models to explore correlates of population change in 1,902 populations of birds and mammals from 447 PAs globally. On an average, we find PAs are maintaining populations of monitored birds and mammals within their boundaries. Wildlife population trends are more positive in PAs located in countries with higher development scores, and for larger-bodied species. These results suggest that active management can consistently overcome disadvantages of lower reproductive rates and more severe threats experienced by larger species of birds and mammals. The link between wildlife trends and national development shows that the social and economic conditions supporting PAs are critical for the successful maintenance of their wildlife populations.
Anthropogenic habitat disturbance is a strong biodiversity change driver that compromises not only species persistence but also the ecological interactions in which they are involved. Even though seed dispersal is a key interaction involved in the recruitment of many tree species and in consequence critical for biodiversity maintenance, studies assessing the effect of different anthropogenic disturbance drivers on this interaction have not been performed under a meta-analytical framework. We assessed the way habitat fragmentation and degradation processes affect species diversity (abundance and species richness) and interaction rates (i.e., fruit removal and visitation rates) of different groups of seed-disperser species at a global scale. We obtained 163 case studies from 37 articles. Results indicate that habitat degradation had a negative effect on seed-disperser animal diversity, whereas habitat fragmentation had a negative effect on interaction rates. Birds and insects were more sensitive in terms of their diversity, whereas mammals showed a negative effect on interaction rates. Regarding habitat, both fragmentation and degradation had a negative effect on seed-disperser animal diversity only in temperate habitats, and negative effects on interaction rates in tropical and temperate habitats. Our results indicate that the impact of human disturbance on seed-disperser species and interactions is not homogeneous. On the contrary, the magnitude of effects seems to be dependent on the type of disturbance, taxonomic group under assessment, and geographical region where the human impact occurs. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Tropical forest understory birds are declining globally for unknown reasons, indicating an urgent need to understand the causes. We review and synthesize studies investigating causes of these declines focusing on the Sarapiquí region of the Caribbean slope of Costa Rica. We discuss evidence for five potential causes of population declines motivated by current understanding of the effects of fragmentation, disturbance of remnant forests, climate change, and their possible interactions: (1) reduced forest area increases the probability of stochastic extirpation; (2) reduced connectivity among forest patches decreases population rescue opportunities; (3) degradation of preferred microhabitats due to, for example, abundant large mammals, jeopardizes specialized birds’ foraging opportunities; (4) high nest predation rates reduce productivity below replacement levels; and (5) changes in macro- and microclimate increase energetic demands and reduce survival. Our review documents how tropical forest loss and degradation likely impact understory birds through a variety of direct, indirect, and interrelated causes spanning multiple temporal and spatial scales and levels of biological organization. We propose that the processes affecting understory birds in the Sarapiquí region may be broadly representative of threats experienced by rainforest understory birds pantropically. Effective conservation will require consideration of such diverse and interacting factors.
Logging and hunting are two key direct threats to the survival of wildlife in the tropics, and also disrupt important ecosystem processes. We investigated the impacts of these two factors on the different stages of the seed dispersal cycle, including abundance of plants and their dispersers and dispersal of seeds and recruitment, in a tropical forest in north-east India. We focused on hornbills, which are important seed dispersers in these forests, and their food tree species. We compared abundances of hornbill food tree species in a site with high logging and hunting pressures (heavily disturbed) with a site that had no logging and relatively low levels of hunting (less disturbed) to understand logging impacts on hornbill food tree abundance. We compared hornbill abundances across these two sites. We, then, compared the scatter-dispersed seed arrival of five large-seeded tree species and the recruitment of four of those species. Abundances of hornbill food trees that are preferentially targeted by logging were two times higher in the less disturbed site as compared to the heavily disturbed site while that of hornbills was 22 times higher. The arrival of scatter-dispersed seeds was seven times higher in the less disturbed site. Abundances of recruits of two tree species were significantly higher in the less disturbed site. For another species, abundances of younger recruits were significantly lower while that of older recruits were higher in the heavily disturbed site. Our findings suggest that logging reduces food plant abundance for an important frugivore-seed disperser group, while hunting diminishes disperser abundances, with an associated reduction in seed arrival and altered recruitment of animal-dispersed tree species in the disturbed site. Based on our results, we present a conceptual model depicting the relationships and pathways between vertebrate-dispersed trees, their dispersers, and the impacts of hunting and logging on these pathways.
In 6 species of fall-fruiting temperate plants, asked whether the percentage of the fruit that was removed was related to the size of the fruit crop. -from Authors
The 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.
Asian hornbill populations are declining across their ranges because of hunting and deforestation. Five of the 32 Asian hornbill species occur in north-east India. However, vital information on their abundance from the region remains scanty. Understanding spatiotemporal variation in densities provides crucial information for formulating effective conservation strategies based on species-specific abundance patterns and population trends. We examined spatiotemporal variation in densities of four hornbill species in the Namdapha Tiger Reserve, a site identified as an important site for hornbill conservation in Asia. We collected data through variable-width line transect sampling (effort=842.1 km) in the non-breeding season from 2009-12 to estimate hornbill densities. We had 458 detections of four hornbill species. We have estimated White-throated Brown Hornbill densities (7.9 birds/km2) for the first time throughout its entire range. The mean Rufous-necked Hornbill densities (6.9 birds/km2) were higher than those reported elsewhere. Great (3.9 birds/km2) and Wreathed Hornbill (16.1 birds/km2) densities were comparable with other sites. The peak densities of all hornbill species in November- December are among the highest reported from Asia. Wreathed Hornbill densities showed temporal variation peaking in November- December (68 birds/km2) and drastically declining by March-April (1.3 birds/km2), indicating seasonal altitudinal movement to lowelevation areas outside the reserve during the breeding season. Our results underscored the spatial variation in hornbill distribution, with low densities of Great and the White-throated Brown hornbills in higher elevations. Our study demonstrates the global importance of Namdapha for hornbills, given its large area and high densities of four hornbill species.
The Western Ghats biodiversity hotspot in India is threatened by habitat loss and fragmentation, which is likely to impact large-bodied, wide-ranging species with specialised requirements such as hornbills.
Forests in Flux
Forests worldwide are in a state of flux, with accelerating losses in some regions and gains in others. Hansen et al. (p. 850 ) examined global Landsat data at a 30-meter spatial resolution to characterize forest extent, loss, and gain from 2000 to 2012. Globally, 2.3 million square kilometers of forest were lost during the 12-year study period and 0.8 million square kilometers of new forest were gained. The tropics exhibited both the greatest losses and the greatest gains (through regrowth and plantation), with losses outstripping gains.
Great and Rhinoceros Hornbills are omnivorous. Food consumed by these two species was studied during the breeding season (January to July of 2003 and 2004) in tropical rainforest, Budo Su-Ngai Padi National Park. The results showed that the Great and the Rhinoceros Hornbills had similar duration of every phase in the breeding cycle, i. e. nest visiting, sealing, incubation, early nestling and late nestling. However, considering the entire breeding cycle, Great Hornbill had signifi cantly shorter cycle (110.6±6.7 days) than that of the Rhinoceros Hornbill (121.7±10.4 days). Total food consumption rate of Great Hornbill was signifi cantly less than (47.0 g/Obs.h.) that of the Rhinoceros Hornbill (62.5 g/Obs.h.), and the diet was comprised of fi g (53.6%), non-fi g (41.5%) and animal (4.9%). Proportion of fi g in the diet of Rhinoceros Hornbill was also signifi cantly higher (72.3%), but similar proportion of non-fi g (23.5 %) and animal (4.2%). Of the total 21 species of non-fi g diet of both Great and Rhinoceros Hornbills in this study, Polyalthia sp. (family Annonaceae) and Aglaia spectabilis (family Meliaceae) dominated fruit food by weight, while millipede dominated animal food. There was no difference in diversity of non-fi g fruit species consumed during all phases between both hornbills except during late nestling. In general, the diet of Great Hornbill has signifi cantly higher diversity than that of Rhinoceros Hornbill. From similarity coeffi cient, it was indicated that they used the same food resources which were mainly available during the study period. This paper was presented at the 5 th International Hornbill Conference jointly organised by the National Parks Board (Singapore) and the Hornbill Research Foundation (Thailand), in Singapore on 22 nd –25 th March 2009.
CONSERVATION ISSUES IN THAILAND Over the past century, the natural resources of Thai-land have been depleted continuously and rapidly, driven by such pressures as population growth, poverty, and globalization, including economic expansion that places overriding importance on the size of the coun-try ' s gross domestic product. By 1985, the government had set a national forest policy target whereby no less than 40% of the country ' s area was to be protected, 15% as conservation forests and 25% as economic forests (RFD, 1985). In the Seventh National Economic and Social Development Plan (1993–1996), the target for conservation of national forest was changed to 25% for conservation forest and 15% for economic forest (NESDB, 2008), still a total of 40% of the total area. By 1989, however, only 28% of the total land area remained forested. To sustain Thailand ' s exceptional species diversity, the government has put a major effort into protecting the forest and its animal inhabitants by various conser-vation measures. Wild animals and their habitats are now completely protected by the National Park Acts (1961) and the revised Wild Animals Reservation and Protection Act (1992). A total of 123 national parks and 58 wildlife sanctuaries have been established in the
The aim of this pilot study was to explore the feasibility of using artifi cial nests for hornbill conservation as well as to develop techniques for their practical usage. The project was divided into three components: 1. To design and implement artifi cial nests for hornbills by using biological data on hornbills as criteria for design; 2. To assess the suitability of the artifi cial nests for hornbills by comparing them with natural nests, using hornbill nesting behavior as a criterion; 3. To study the correlations between some environmental factors and the hornbills' selection of nest cavities. This paper covers the fi rst part of the project and includes some preliminary results from work during the period 2003 to 2009. The design of artifi cial nest in this study covers not only hornbill requirements, but also various practical issues related to this design, i.e., production feasibility, transportation to the sites, and installation. The anticipated outcome of this study is the ready-made nest that can serve both hornbill requirements and installation process. Nineteen artifi cial nests were permanently installed at Budo-Su-Ngai Padi National Park, Southern Thailand in the year 2005 and observation of artifi cial nests during the breeding season has been conducted since then. The fi rst pair of hornbills entered an artifi cial nest in 2006. Since then, the use of artifi cial nests by hornbills has been increasing steadily. The data obtained from this long-term observation will be used to assess the suitability of the artifi cial nest and to develop future artifi cial nest designs. This paper was presented at the 5 th International Hornbill Conference jointly organised by the National Parks Board (Singapore) and the Hornbill Research Foundation (Thailand), in Singapore on 22 nd –25 th March 2009.
Many hornbill species in Thailand are categorized as Endangered or Critically Endangered on the IUCN Red List. The objectives of this research were to predict hornbill distributions in Thailand and to assess the national conservation status of the species using extent of occur-rence. We employed maximum entropy modelling, using 10 environmental variables that were believed to directly or indirectly influence hornbill distributions across Thailand, to predict the habitats potentially suitable for 10 of the country's 13 hornbill species. Data on the presence of hornbills were gathered from the Thailand Hornbill Project and additional field surveys in protected area complexes during 2004–2006. The results indicated that patch size is the most important factor affecting distribution, followed by latitude, ecoregion and distance to villages. All hornbill species were predicted to occur primarily in intact protected area complexes. The total extent of all hornbill habitats covers 9.3% of the country's land area. Seven of the 10 modelled species are at risk and the current distri-bution pattern is expected to reflect stochastic extinctions because of small population size. We recommend that the conservation status of Austen's brown hornbill Anorrhinus austeni and Tickell's brown hornbill Anorrhinus tickelli should be changed from Vulnerable to Endangered. The model identified five protected area complexes as hornbill hotspots in Thailand. These findings will help guide conservation management.
Hornbills, the largest birds of Asian tropical forests, are ideal flagship species. Budo Mountain supports six sympatric hornbill species, of which Rhinoceros Hornbill Buceros
rhinoceros and Helmeted Hornbill Rhinoplax
vigil are locally endangered. Because hornbills rely on a cavity in a large tree for nesting, the combination of forest encroachment and poaching could extirpate them from Budo. To increase and sustain hornbill populations, we set two phases of approach, immediate and long-term. Since 1994, 50 ex-poachers and/or illegal loggers from 13 villages around Budo were persuaded to participate in research and conservation programs together with urban people. These were based on hornbill nest adoption, with 1,774 nest-years of adoption now accrued that provide an essential data base and major source of funding. Within 90 km2 of Budo rainforest, villagers have located 189 nest trees, among which an average of 38 nests were used annually. Despite difficulties within the area, including natural problems and situations of social unrest, a cumulative total of 1,170 nest-cavity-years have been recorded by the villagers, and at least 490 chicks have fledged. The program is considered successful in terms of poaching eradication and has led to the establishment of the Budo Hornbill Conservation & Education Center in 2004 on a piece of land donated by a villager’s family. The Center provides educational and conservation lessons to schoolteachers, children, teenagers and villagers in the surrounding area for approximately 400 individuals per year, and could be a model for conservation programs of other large but critically endangered bird species.
Ranges of individual males of three hornbill species were determined by radio telemetry during the breeding and non-breeding seasons in Khao Yai National Park, Thailand. Two Great Hornbills Buceros bicornis and two Brown Hornbills Ptilolaemus tickelli were studied in both 1988 and 1989, and two Wreathed Hornbills Rhyticeros undulatus were studied in 1989, 1990 and 1991.
In the breeding season, the home range of the Great Hornbill was 3.7 km2, similar to that of the Brown Hornbill (4.3 km2), while the Wreathed Hornbill occupied the largest home range (10.0 km2). In the non-breeding season, the range size of the Wreathed Hornbill (28.0 km2) was greater than that of the Great Hornbill (14.7 km2). Differences in range sizes of different species may be related to differences in diet and breeding strategy. Ranges overlapped within and between the species, and this has implications for the estimation of the minimum area required for the conservation of hornbills within the Khao Yai National Park.
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.
The responses of hornbills to selective logging were determined by comparing their diversity 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 a plantation in Pakhui Wildlife Sanctuary adjoining reserve forests in western Arunachal Pradesh. The species recorded were the Oriental pied hornbill Anthracoceros albirostris wreathed hornbill Aceros undulatus great hornbill Buceros bicornis. The great hornbill was the most common species overall 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 river-margin 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 movement patterns differential vulnerability to hunting disturbance. Great hornbill abundance was correlated with large tree density (GBH &;ge 150 cm) 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 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.
1.Distance sampling is a widely used technique for estimating the size or density of biological populations. Many distance sampling designs and most analyses use the software Distance.
2.We briefly review distance sampling and its assumptions, outline the history, structure and capabilities of Distance, and provide hints on its use.
3.Good survey design is a crucial prerequisite for obtaining reliable results. Distance has a survey design engine, with a built-in geographic information system, that allows properties of different proposed designs to be examined via simulation, and survey plans to be generated.
4.A first step in analysis of distance sampling data is modelling the probability of detection. Distance contains three increasingly sophisticated analysis engines for this: conventional distance sampling, which models detection probability as a function of distance from the transect and assumes all objects at zero distance are detected; multiple-covariate distance sampling, which allows covariates in addition to distance; and mark–recapture distance sampling, which relaxes the assumption of certain detection at zero distance.
5.All three engines allow estimation of density or abundance, stratified if required, with associated measures of precision calculated either analytically or via the bootstrap.
6.Advanced analysis topics covered include the use of multipliers to allow analysis of indirect surveys (such as dung or nest surveys), the density surface modelling analysis engine for spatial and habitat modelling, and information about accessing the analysis engines directly from other software.
7.Synthesis and applications. Distance sampling is a key method for producing abundance and density estimates in challenging field conditions. The theory underlying the methods continues to expand to cope with realistic estimation situations. In step with theoretical developments, state-of-the-art software that implements these methods is described that makes the methods accessible to practising ecologists.
Monitoring of biodiversity and resource use by professional scientists is often costly and hard to sustain, especially in
developing countries, where financial resources are limited. Moreover, such monitoring can be logistically and technically
difficult and is often perceived to be irrelevant by resource managers and the local communities. Alternatives are emerging,
carried out at a local scale and by individuals with little formal education. The methods adopted span a spectrum, from participatory
monitoring where aims and objectives are defined by the community, to ranger-based monitoring in protected areas. What distinguishes
these approaches is that local people or local government staff are directly involved in data collection and (in most instances)
analysis. In this issue of Biodiversity and Conservation, 15 case studies examine whether these new approaches can address
the limitations of professional monitoring in developing countries. The case studies evaluate ongoing locally-based monitoring
schemes involving more than 1500 community members in 13 countries. The papers are based on a symposium held in Denmark in
April 2004 (www. monitoringmatters.org). Here, we review how the case studies shed light on the following key issues concerning
locally-based methods: cost, sustainability, their ability to detect true local or larger-scale trends, their links to management
decisions and action, and the empowerment of local constituencies. Locally-based monitoring appears to be consistently cheap
relative to the costs of management and of professional monitoring, even though the start-up costs can be high. Most local
monitoring schemes are still young and thus their chances of being sustained over the longer term are not yet certain. However,
we believe their chances of surviving are better than many professional schemes, particularly when they are institutionalised
within existing management structures, and linked to the delivery of ecosystem goods or services to local communities. When
properly designed, local schemes yield locally relevant results that can be as reliable as those derived from professional
monitoring. Many management decisions emanate from local schemes. The decisions appear to be taken promptly, in response to
immediate threats to the environment, and often lead to community-based actions to protect habitats, species or the local
flow of ecosystem benefits; however, few local schemes have so far led to actions beyond the local scale. Locally-based monitoring
schemes often reinforce existing community-based resource management systems and lead to change in the attitude of locals
towards more environmentally sustainable resource management. Locally-derived data have considerable unexplored potential
to elucidate global patterns of change in the status of populations and habitats, the services they provide, and the threats
they face, but more effort is needed to develop effective modalities for feeding locally-derived data up to national and international
levels.
Biotic seed dispersal of plants is a complex phenomenon that is influenced by multiple seed disperser species with implications for plant fitness and range expansions. While inter-species variation has been well-studied, the importance of incorporating intraspecific variation in seed dispersal is increasingly being acknowledged. We compared seed dispersal patterns of breeding and non-breeding great hornbills Buceros bicornis and a breeding wreathed hornbill Rhyticeros undulatus by combining data on fruiting tree visitations, gut passage time and movement data from tagged hornbills. Seed dispersal probability at nest trees (by breeding males) was low (<12%) suggesting that males scatter-disperse seeds, unlike breeding females that deposit seeds below nest trees. Median seed dispersal distance of great hornbills was 294 m and 254 m in the breeding and non-breeding season respectively, and, the distribution tail was shorter for breeding birds (2.5 km) than non-breeding birds (13 km). The median and maximum seed dispersal distance by the wreathed hornbill was 1.35 km and 11 km respectively. This study highlights intraspecific variation in seed dispersal patterns across sexes and breeding and non-breeding male hornbills and potential variation between two hornbill species. This is the first study that estimates long-distance seed dispersal by Asian hornbills.
Tropical forests are on the front lines of the current global extinction crisis. Species with restricted habitat requirements and slow reproductive rates, such as the spectacular hornbills (Bucerotidae) of the Paleotropics, are particularly vulnerable. We present the first long-term quantitative population assessment of nine forest hornbill species in Ghana, part of the Upper Guinea forest biodiversity hotspot in West Africa. From 1990 to 2009, hornbill encounter rates declined with 32–88% across eight species found in the region. Seven separate surveys between 1990 and 2014 indicated declines in at least six of eight species detected, with large-bodied species hardest hit. Depleted remnant populations of large hornbills mainly persist in two large and relatively well-protected wildlife reserves, Ankasa Resource Reserve and Kakum National Park. Contrastingly, the five largest species of the nine hornbills known to Bia Biosphere Reserve, one of Ghana's few forest wildlife reserves, apparently vanished completely since the 1990s, mainly due to uncontrolled hunting. Similarly, several large hornbills have disappeared from forest reserves where hunting is widespread. We conclude that uncontrolled hunting is the major driver of the recent drastic declines and population extirpations of large hornbills, while reductions in small insectivorous species may be related to extensive fragmentation and habitat disturbances of the Ghanaian forest biome. We call for urgent conservation action to prevent further declines and impending extirpations of forest hornbills and other wildlife in West Africa.
Demand for the ‘ivory’ casques of the Helmeted Hornbill
Rhinoplax vigil
appears to have risen very sharply, although the species is legally protected in every range state (Brunei, Indonesia, Malaysia, Myanmar, Thailand) and it is on Appendix I of CITES. Seizure records and other sources indicate that the majority of hornbills are being killed in Indonesia on the islands of Borneo and Sumatra and smuggled to China where the casques are carved for commercial sale. Between March 2012 and August 2014 a minimum 2,170 heads and/or casques were seized from the illegal trade in Indonesia and China in identifiable enforcement actions. Seizures were made from poachers, smugglers, processing facilities and retailers (both physical shops and online traders). Thirteen seizures occurred in Indonesia in which no fewer than 1,117 specimens were confiscated. In China, 18 seizures resulted in the confiscation of 1,053 specimens. Anecdotal evidence suggests the species is now rare in Indonesia but that demand, reflected in the high prices involved, will not soon abate. Efforts are therefore urgently needed to end this illegal trade, which is controlled by organised crime with interests in other wildlife products, to advertise the penalties for transgressors, and to create awareness of the law and the plight of the species among potential consumers.
We conducted surveys for nocturnal birds (Strigiformes, Caprimulgiformes) at Bala rainforest, southern Thailand, in the ten lunar months from March to November 2004, mainly between dusk and midnight of successive nights in the week preceding full moon. At 0.5-km intervals along the 12.6 km of road that bisects Bala, we listened for calls both before and after broadcasting a 1-min recording of the loud call for each of the species that we expected. We also searched, by day and on non-survey nights, for additional signs of nocturnal species along or near the road, especially of Buffy Fish Owl Ketupa ketupa and nightjars. From all detections of a species, whether heard calling, responding to our broadcast, or seen, we estimated its distribution, temporal and spatial relative abundance, and density along the road. Two species were new records for Bala, Oriental Bay Owl Phodilus badius and Brown Wood Owl Strix leptogrammica. Two small insectivorous species were the most widespread and abundant, Collared Scops Owl Otus bakkamoena and Javan Frogmouth Batrachostomus javensi, at -8.0/km2 and -5.5/km2, respectively. We detected three medium-sized to small species, Oriental Bay Owl, Reddish Scops Owl Otus rufescens and Brown Hawk Owl Ninox scutulata, as well as a possible fourth species, Gould's Frogmouth Batrachostomus stellatus, only in lowland forest below ~300 m asl; all were at low overall densities of -1.6/km2. Three large species also occurred at low densities, but probably as widely spaced territorial pairs along the road: Barred Eagle Owl Bubo sumatranus at ≤ -2.5 km/ pr, Brown Wood Owl Strix leptogrammica at ≤4.2 km/pr, and Buffy Fish Owl at ≤2.5 km/pr, the last estimated from spacing of signs along streambeds. Smaller species were most vocal during the middle of the dry season (May) and larger species during the south-west monsoon (August-September). Grey Nightjar Caprimulgus indicus was the only common caprimulgid, a boreal migrant detected during November to April. Our results are useful for preliminary ecological and management analyses, but require repetition, refinement of technique and comparison with results from different Indomalayan forests to improve their applicability.
Factors limiting seed germination and seedling establishment of the hemiepiphyte Ficus stupenda were investigated with two field experiments conducted in a Bornean rain forest canopy. In Experiment I, seeds of F. stupenda were planted in potential establishment sites averaging 31 m above the ground in each of 45 dipterocarp trees. Twenty seeds each were planted in a total of 336 sites. Germination, survivorship, and growth were monitored over 1 yr, and examined in relation to microsite and host tree characteristics. The presence of substrate with good moisture retention (soil, rotting wood, or moss) was the most important factor for germination. Such substrates were most frequently associated with knothole sites in the canopy, which had the highest level of establishment success. Seedling survival to 12 mo was low (1.3% of planted seeds), especially considering that the best available sites in each tree were selected. Only 0.04% of seedlings showed vigorous growth after 12 mo. A seed-harvesting ant in the genus Pheidole significantly reduced germination success, and herbivory and desiccation killed many seedlings at later stages. In Experiment 2, seedling growth in natural canopy sites was compared with growth of seedlings in artificial planter boxes raised into the canopy in order to assess the relative quality of canopy sites. Planters were superior to natural sites for seedling survivorship and supported much more rapid seedling growth with a positive response to light level. Higher growth rates in planters compared with natural sites showed that water stress appeared to be the critical factor limiting seedling growth in the canopy, even in this very wet climate. Sites in the canopy with the optimal combination of conditions for fig seedling establishment appear to be very scarce. Ficus population densities may be limited by both biotic and abiotic factors reducing early recruitment success.
Quantifying ecosystem functions in spatially explicit ways is important for management decisions in increasingly fragmented landscapes. Between‐patch dispersal of seeds by frugivores constitutes a key ecosystem function to ensure connectivity for fleshy‐fruited plants. However, to date, methodological hurdles have limited our understanding of dispersal pathways on the landscape scale.
We made use of newly available tracking devices and combined movement data of 30 trumpeter hornbills B ycanistes bucinator with gut passage times and high‐resolution habitat data in a fragmented forest landscape in S outh A frica. We identified each potential seed dispersal path and distinguished whether potential seed transport happened to a different forest patch (between‐patch dispersal), within the same patch (within‐patch dispersal) or into the habitat matrix (failed dispersal). To quantify functional landscape connectivity, we identified all possible between‐patch connections and used graph networks to estimate landscape connectivity provided by hornbills.
Although potential between‐patch dispersal events were rare (on average 7% compared to 20% failed dispersal and 73% within‐patch dispersal), hornbills could cover distances of up to 15 km. Hornbills visited over 100 forest patches and connected a habitat network with an extent of about 50 km, which increased the potential functional connectivity of the landscape more than twofold.
We identified habitat patches that were critical stepping stones for seed dispersal pathways. Without these stepping stones, the network would likely disintegrate into separated components and lead to isolation of forest fragments.
Synthesis and applications . We showed that large frugivorous birds can greatly improve functional connectivity for fleshy‐fruited plants across broad scales, linking habitat patches in fragmented forest landscapes. Combining high‐resolution movement and landscape data in graph networks allows identifying seed dispersal pathways and critical stepping stones in fragmented landscapes. This approach addresses the general challenge of spatially explicit mapping of ecosystem services and can be widely incorporated in reserve design and landscape‐level conservation planning.
Hornbills are useful indicators of forest condition and human disturbance because they require large tracts of unfragmented forest with large fruiting trees for feeding and nesting. They are relatively large-bodied, which makes them targets for hunting. Density estimates of such species are critical for population monitoring and serve as a baseline against which future changes can be measured. In this study we used variable-width line transect surveys to estimate the densities of nine hornbill species in the Bala portion of the Hala-Bala Wildlife Sanctuary on the Thai–Malaysia border, one of the few remaining areas of lowland forest in Thailand. The hornbill species were: Rhinoceros (Bucerosrhinoceros), Great (B.bicornis), Helmeted (B.vigil), Black (Anthracocerosmalayanus), Bushy-crested (Anorrhinusgaleritus), White-crowned (Aceroscomatus), Wrinkled (A.corrugatus), Wreathed (A.undulatus) and Plain-pouched (A.subruficollis). Between January 2001 and April 2002, 11 transects along trails, old logging roads and one paved road were surveyed once per month. A total of 1,261 observations of the nine species were made during the observation period. Estimates for Rhinoceros and Helmeted Hornbill were 2.69 and 1.21 individuals/km2, respectively, and were similar or slightly higher than densities reported elsewhere. Estimates for Great (0.12), Bushy-crested (0.64), Wrinkled (0.08), White-crowned (0.08) and Wreathed Hornbills (0.69) were generally lower than estimates from other areas in the region. It was not possible to obtain density estimates using distance sampling for Black and Plain-pouched Hornbills due to the small number of observations, but our data did suggest that their densities were also low (<0.10 individuals/km2). Potential reasons for differences between this and other areas include a scarcity of lowland habitat, habitat isolation, lower abundance of specific fruit resources and interspecific competition, but these factors require further investigation. Standardization of survey techniques among studies would significantly improve assessments of habitat requirements as well as of the effects of human disturbance on Asian hornbills, most of which are globally threatened. Our study specifically underscores the need for additional research on the Plain-pouched Hornbill, the most threatened of the species studied, as density estimates from elsewhere in its range are lacking, while more generally it highlights the need to investigate the underlying causes of the often substantial variation in hornbill densities among species and sites.
I summarize the current knowledge of frugivory and seed dispersal by hornbills in tropical forests. Many studies report on frugivory by hornbills but few specifically identify hornbills as effective dispersers. Hornbills are able to disperse a diverse array of fruits in tropical forests (748 plant species from 252 genera and 79 families) and move many of the seeds far from the parent trees. They digest only the fleshy parts of fruits that they swallow and then regurgitate/defecate the seeds intact. The relatively long seed retention times (>1 h) and propensity for depositing seeds away from the parent trees while foraging suggest high-quality dispersal. Some seeds might be aggregated at nest and roost sites, but hornbills are capable of dispersing seeds over several kilometers, resulting in a relatively even spread of seeds throughout the forest. Based on the results summarized here, hornbills provide excellent seed dispersal services to tropical plants in their respective habitats.
In many bird monitoring surveys, no attempt is made to estimate bird densities or abundance. Instead, counts of one form or another are made, and these are assumed to correlate with bird density. Unless complete counts on sample plots are feasible, this approach can easily lead to false conclusions, because detectability of birds varies by species, habitat, observer and many other factors. Trends in time of counts often reflect trends in detectability, rather than trends in abundance. Conclusions are further compromised when surveys are conducted at unrepresentative sites. We consider how to avoid these problems. We give a brief description of distance sampling methods, which allow detectability to be estimated. We consider strategies to ease their implementation, to enhance their reliability, to adapt the methods for difficult species, and to deal with circumstances in which representative sampling is problematic. We also consider some of the common problems encountered, and suggest solutions.
Phenological observations were made in a Sumatran rain forest during three years (1980–1982). Phenological changes followed a consistent seasonal pattern. The abundance of young leaves and the fall of leaf litter peaked between December and February (first dry season); flowers were most abundant between January and April (first dry and first wet sea son), and ripe fruits in July-August (the second dry season). The fruit of strangling fig trees showed peaks in April and October, both wet season months. Within the study area there was variation in both the phase and the amplitude of the phenological cycles. One year, 1981, displayed mast flowering and fruiting. The observations indicate that the conditions for production were better during the mast year, a finding that facilitates our understanding of the evolution of mast fruiting.
Distance sampling is a widely used group of closely related methods for estimating the density and/or abundance of biological populations. The main methods are line-transect sampling and point-transect sampling. In both cases, observer(s) perform a standardized survey along a series of randomly located lines or points, searching for objects of interest (usually animals or clusters of animals). For each object detected, they record the distance from the line or point to the object. Not all objects will be detected, but a fundamental assumption of the basic methods is that all objects that are actually on the line or point are detected. The key to distance sampling analyses is to use the observed distances to fit a detection function that describes how detectability decreases with increasing distance from the transect. The fitted function is used to estimate the average probability of detecting an object; from here, one can readily obtain point and interval estimates for the density and abundance of objects in the survey area. Various extensions to the basic methods allow assumptions to be relaxed, and include methods that integrate capture-recapture and distance sampling, as well as methods to model spatial variation in density.
Reduced Emissions from Deforestation and Forest Degradation in Developing Countries (REDD+) is a policy mechanism now agreed under the United Nations Framework Convention on Climate Change (UNFCCC). It aims to reduce carbon dioxide emissions from developing countries through the sustainable management of forests, while providing co-benefits of biodiversity conservation and livelihood support. Implementation challenges include linking remote sensing and national forest inventories of carbon stocks, to local implementation and measuring carbon loss from forest degradation. Community-based forest monitoring can help overcome some of these challenges. We show that local people can collect forest condition data of comparable quality to trained scientists, at half the cost. We draw on our experience to propose how and where local REDD+ monitoring can be established. Empowering communities to own and monitor carbon stocks could provide a rapid and cost-effective way of absorbing carbon dioxide emissions, while potentially contributing to local livelihoods and forest biodiversity conservation.
We estimated densities of parrot and hornbill species in primary and selectively logged forest and forest gardens at two lowland sites on New Britain, PNG. We related differences in abundance to food and nest-site availability in the different habitats and determined whether nest-site availability might limit local breeding populations. Blue-eyed Cockatoo Cacatua ophthalmica and Blyth's Hornbill Rhyticeros plicatus were usually rarer in forest gardens than in primary forest, but both fared well in logged forest. Eclectus Parrot Eclectus roratus was more common in all human-altered forests than in primary forest, and Eastern Black-capped Lory Lorius hypoinochrous was reasonably common throughout but extremely abundant in forest gardens at one site. Parrots and hornbills were recorded eating fruits of 15 tree species and flowers of nine species. Densities of these fruiting and flowering trees were highest in logged forest and forest gardens, respectively, indicating the importance of these anthropogenic habitats as feeding grounds for the assemblage. Active nest cavities were found in large individuals of 12 tree species. Densities of potential nest cavities were highest in primary forest and lowest in forest gardens. At both sites, estimates of potential nest-site density were significantly lower than estimates of the density of pairs of all species of parrots and hornbills: there may be 10–20 parrot/hornbill individuals per nest-hole. Continuing forest alteration, whilst further reducing nest-site availability, may allow large populations of parrots and hornbills to persist due to increased availability of food in some anthropogenic habitats. However, current abundance of such bird species may be a poor correlate of future extinction risk as long-lived taxa may remain common for some period even when annual recruitment has declined to critically low levels.