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Rapid assessment of two sympatric species populations and their nesting behaviour in Zhemgang district,

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PROJECT REPORT Rapid assessment of two sympatric hornbill species populations and their nesting behaviour in Zhemgang district, Bhutan

KARMA SHERUB & SANGAY TSHERING

Introduction Study area are specialists in terms of their habitat, The study area is in southern Bhutan, bordering food and nest-site requirements, and play a very the state of Assam, . The altitude ranges important role in the ecosystem as seed from under 200 m in the south to over 2,000 m in dispersers (Kemp 1995, Kinnaird & O’Brien 2008, the north. Most of the area is in the contiguous Krishna et al. 2012). The of Bhutan hold four Jigme Singye Wangchuck National Park and species— Rhyticeros undulatus, Royal Manas National Park. The topography is albirostris, rugged in most parts, dominated by broadleaf Rufous-necked Hornbill Aceros nipalensis and species. This area is mainly used for feeding, Buceros bicornis (Clements 1992, nesting and roosting by the hornbills due to the Webster 2011); the present study was carried presence of large for cover and diverse out on the latter two species, both of which are fruiting tree species (Sherub 2017). The survey easily detected due to their large size and loud focused mainly on the buffer zone (forested calls (Poonswad et al. 1987, 2013). However, due areas near human settlements) for the long-term to anthropogenic interference, both species are protection of hornbills in the peripheral areas under threat and are today classified as Vulnerable rather than the undisturbed primary forest, with (BirdLife International 2019a,b). This study reports the objective of conserving the buffer zone. on the distribution, abundance, nesting behaviour, habitat characteristics and anthropogenic threats Methods to Rufous-necked Hornbill and Great Hornbill in A reconnaissance survey involving local people Zhemgang district, Bhutan. was done to find active nests of Great Hornbill

Figure 1. Distribution of Great Hornbill Buceros bicornis and Rufous-necked Hornbill Aceros nipalensis in sampling sites in Zhemgang district, Bhutan. BirdingASIA 31 (2019) 55 and Rufous-necked Hornbill during the breeding The study covered eight locations which were season—March to July 2017. Short term observations identified as important hornbill habitats during were carried out at active nesting sites of both questionnaire sessions and the preliminary survey species to document their breeding behaviour with the local residents (Table 1). During the non- from the time of nest entry until the fledging of breeding season, from August to November 2017, juveniles. Food resources consumed were recorded eight transects between 10 and 30 km long were by observation of the hornbills at feeding sites walked a total of four times each, between 07h00 and collection of regurgitated seeds and and 16h00. All hornbills seen on both sides of the remains below the nesting holes. transect lines were counted (Figure 1, Table 1). The flock size was counted when groups of hornbills were seen feeding and/or resting on fruiting trees Table 1. Records of Rufous-necked Hornbill Aceros nipalensis or flying over. (RH) and Great Hornbill Buceros bicornis (GH) in areas surveyed The most abundant tree species found at the during the non-breeding season; August to November 2017, sampling sites (greater than 30 cm DBH) were Zhemgang district, Bhutan. Km = transect length (kilometres). recorded based on the information provided by residents, and images were taken or samples collected No. seen Location transect for later identification. The research documented description Km Date (2017) RH GH 42 tree species which were commonly found in the Kikhar 1 August 2 - areas from information gathered from local residents. Dakphai to Kihar road 2 August 1 - The immediate threats to the feeding, nesting 20 5 October 1 - and survival of hornbills were recorded based on observations during the entire survey period. 28 November 2 - Wangdigang 13 August - 2 Results and discussion Tingtibi to 14 August - - Nesting records and breeding behaviour 15 Wangdigang road 8 October - 3 Seven nests were monitored during the current 26 November 2 2 research: two were occupied by Great Hornbill and five by Rufous-necked Hornbill (Table 2). However, Tama 19 August 9 3 due to repeated disturbance by road construction/ Tingtibi to Tama road 20 August 6 - 30 maintenance work, one of the Rufous-necked 11 October 7 - Hornbill nest-sites was out of use during the survey 19 November 3 1 period. Both species commenced breeding in early Goling 5 September - 6 April, with the female being successfully sealed-up Tingtibi to Goling 6 September - 5 in the nest hole late in the month and the fledging road 13 of juveniles in late July to early August—a breeding 19 October 1 7 period of more than 100 days. Both species preferred 16 November - 5 big trees with large holes for nesting. Gomphu 12 September 6 4 Goling to Gomphu 15 September 2 2 25 Table 2. Structural characteristics of hornbill nests, zeropoint road 22 October 9 4 Zhemgang district, Bhutan. 9 November 4 3 Key: DBH = trunk diameter at breast height; 13 September 7 - Dist.(m) = distance of tree from transect. * inactive nest Gomphu to 14 September 11 - 10 Cavity Citybrang walking 23 October 5 - Nest Tree DBH height Dist. Altitude trail 10 November 3 - location height (m) (cm) (m) (m) (m) Pantang 21 September 2 - Rufous-necked Hornbill Gomphu to Pantang 24 September - - Kikhar 30 111 23 50 1,609 27 highway 3 November 2 - Tama 25 105 10 20 1,449 6 November - - 26 98 9 1 1,424 Goshing 22 September 7 2 Gomphu 10* 56 2 10 959 Goshing to 23 September 5 2 27 107 15 8 692 24 Mewagang farm road 4 November 3 - Great Hornbill 5 November 6 - Tingtibi 27 101 15 2 712 32 days 106 51 Goshing 33 121 21 5 564 56 Rapid assessment of two sympatric hornbill species populations and their nesting behaviour

Pre-nesting behaviour of both species started population size is generally affected by factors with the male hopping laterally over the female to such as type of vegetation, habitat, temperature, land on the same branch and repeating the action availability of food, size of forest area and tall from alternate sides three or four times, followed old trees with natural holes (Wagh et al. 2015). by the female entering the nest and then the Sherub (2017) also recorded competition for food sealing process, during which the male was seen and nesting holes. bringing mud to seal the nest with the female’s Ten similar fruit species were recorded as being assistance. At night the males of both species consumed by both the hornbill species during this roosted elsewhere. The male fed the female 3 to 6 work— lawii, Aphanamixis polystachya, times each day between 07h00 and17h00 until the Beilschmiedia gammieana, Canarium strictum, juveniles fledged, similar to earlier observations Choerospondias axillaris, Elaeocarpus lanceifolius, by Sherub (2017) benghalensis, Ficus roxburghii, Phoebe spp. It was observed that both the hornbill species and Terminalia chebula. Other food items supplied continued to feed their juveniles in the nest-hole during the breeding season included chicks of for 3–6 days after the female broke out of the nest. unidentified small avian species and invertebrates In the case of Rufous-necked Hornbill, the female such as caterpillars. then refrained from feeding the juvenile for a day to encourage it out of the nest, whereas in the case Conservation threats of the Great Hornbill, the mother fed the juvenile Availability of nesting holes was a major constraint with only a few fruits and then did not feed it again, on nesting and was compounded by the various also to encourage it to depart the nest. After the anthropogenic activities in the study area. Ongoing juvenile emerged from the nest, it stayed for 6 to 7 road widening and maintenance during the breeding hours in low branches, where the parents came to season disturbed the breeding cycle—the inactive feed it whilst encouraging it to move to the higher Rufous-necked Hornbill nest at Gomphu had been branches by cawing. active three years previously but was abandoned To date, only one chick has been fledged due to frequent disturbances (pers. obs.); conversely, successfully from each nest observed. It was a nest located just one metre from a farm road, but noted that there were moulted feathers beneath infrequently used by humans, was still active, the nest cavity of Rufous-necked Hornbill during indicating that frequent human activity is another the breeding season (Plate 4). No predators that major constraint for nest-use and breeding success might pose a threat to the incubating female were by hornbills; this was also observed in Jigme Singye recorded. Wangchuck NP (Sherub 2017). The study assumed that where hornbills are The evident main cause of habitat destruction present in suitable habitat, the probability of nest was the cutting down of fruiting tree species (both occurrence is high. Based on the observation mature and saplings) by cattle herders and other of hornbills flying over the higher altitude local people. For example, people were seen cutting undisturbed forest at dawn, it appeared that the down branches and new growth of Persea spp.—an were nesting in inaccessible forested areas abundant and important part of the diet of hornbills out of the reach of human disturbance. and other wildlife species—to collect the fruits as a source of income. Such activities pose immediate Distribution and sight records threats to all wildlife species. Another factor A total of 106 Rufous-necked Hornbill and 51 leading to the abandonment of nest-sites mentioned Great Hornbill sightings were made during the by residents was the frequent disturbance of the overall survey period, at altitudes between 249 nesting female by curious humans due to a lack and 1,726 m, appearing to confirm that there were of awareness of the importance of wildlife in the more Rufous-necked Hornbills than Great Hornbills ecosystem. in the current study area. Rufous-necked Hornbill was seen at all the sampling sites, while Great Conclusion and recommendations Hornbill was less widely distributed, occurring The majority of the study area has forest cover only at Wangdigang, Tama, Gomphu and Goshing including core (primary forest) and buffer (Table 1). There were 25 sightings of Rufous- (habitat used by humans and wildlife) zones, necked Hornbill at Tama and Gomphu, whilst there both comprising the habitats of hornbills. The were 23 Great Hornbill sightings at Goling. Both core habitats are inaccessible to most humans due species were seen in pairs throughout the year to the rugged topography of the area. Although and occasionally in flocks of 3 to 9 individuals, the core habitat is safe at present, it will require especially during the non-breeding season, as more rigorous protection as the destruction of also noted by Sherub (2017). However, hornbill more readily accessible resources forces the BirdingASIA 31 (2019) 57 NAMGAY DORJI Plate 1. Flock of Great Hornbill Buceros bicornis feeding on fruits, Zhemgang district, Bhutan, 1 August 2017. NAMGAY DORJI Plate 2. Flock of Rufous-necked Hornbill Aceros nipalensis feeding on fruits, Zhemgang district, Bhutan, 27 September 2017.

ever-growing population to start encroaching on zones and habitat improvement in buffer zones, the less accessible areas in their desperation to leading to the sustainability of these resources. survive. Consequently, it is important to focus In view of the current conservation threats, research in the buffer zones (where wildlife and general recommendations for the conservation of humans collide) so that the habitat there can hornbills are the protection of old growth forest be improved/managed by sensitising, teaching patches, systematic surveys to locate nests, regular and training the human inhabitants about the monitoring and protection of nest trees and the importance of trees and wildlife in the ecosystem. execution of long-term studies on the breeding This would ultimately lead to protection of core biology of hornbills. 58 Rapid assessment of two sympatric hornbill species populations and their nesting behaviour NAMGAY DORJI NAMGAY DORJI Plate 3. Nest-hole of Rufous-necked Hornbill, Zhemgang Plate 5. Male Rufous-necked Hornbill feeding fruit to the district, 1 August 2016. female inside the nest, Zhemgang district, 9 August 2017.

Clements, F. (1992) Recent records of birds from Bhutan. Forktail 7: 57–73. Kemp, A. (1995) The hornbills. Oxford: Oxford University Press. Kinnaird, M. & O’Brien, T. (2008) The ecology and conservation of Asian hornbills: farmers of the forest. Chicago: University of Chicago Press. Krishna, C. M., Sarma, K. & Kumar, A. (2012) Rapid assessment of Wreathed Hornbill Aceros undulatus (Aves: Bucerotidae) populations and conservation issues in fragmented lowland tropical forests of Arunachal Pradesh, India. J. Threatened Taxa 4(14): 3342–3348. Poonswad, M. K., Kemp, A. & Strange, M. (2013) Hornbills of the word: a photographic guide. : Draco Publishing & Distribution. Poonswad, P., Tsuji, A. & Ngampongsai, C. (1987) A comparative study on breeding biology of four sympatric hornbill species (Family NAMGAY DORJI Plate 4. Moulted feathers of Rufous-necked Hornbill below Bucerotidae) in with implications for breeding in captivity. the nest-hole, Zhemgang district, 20 September 2017. California: International Foundation for the Conservation of Birds. Sherub, K. (2017) Foraging behavior, food resources, and habitat use of Rufous-necked hornbill (Aceros nipalensis) in Jigme Singye Wangchuck Acknowledgements National Park, Bhutan. London: Rufford Foundation. Our thanks go to the Department of Forest Wagh, G. H., Wadatkar, J. D. & Kasambe, R. M. (2015) Status and and Park Services, the Royal Manas National distribution of Anthracoceros coronatus Park, the Wildlife Conservation Division and the in Melghat Tiger Reserve, Maharashtra. Int. J. , Anim. & Env. Ugyen Wangchuck Institute for Conservation and Sci. 5(3): 60–69. Environmental Research for permission to carry Webster, R. (2011) Field guides; birding tours worldwide. Accessed at out this project. We also thank the Oriental http://www.fieldguides.com/triplists/bhu11LIST.pdf on 13/05/2017. Club and the March Conservation Fund of the Tides Foundation for financial support. Finally, we would Karma SHERUB like to thank the staff of Royal Manas National Park Department of Forestry, College of Natural and Jigme Singye Wangchuck National Park and all Resources the local people in the study area for their assistance Lobesa, Punakha, Bhutan in the successful completion of this work. Email: [email protected]

References Sangay TSHERING BirdLife International (2019a) Species factsheet: Aceros nipalensis. Department of Sustainable Development, College Accessed at http://www.birdlife.org on 30/06/2019. of Natural Resources BirdLife International (2019b) Species factsheet: Buceros bicornis. Lobesa, Punakha, Bhutan Accessed at http://www.birdlife.org on 30/06/2019. Email: [email protected]

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