Spatial and Temporal Variation in Hornbill Densities in Namdapha Tiger Reserve, Arunachal Pradesh, North-East India

Abstract

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/km 2 ) for the first time throughout its entire range. The mean Rufous-necked Hornbill densities (6.9 birds/km 2 ) were higher than those reported elsewhere. Great (3.9 birds/km 2 ) and Wreathed Hornbill (16.1 birds/km 2 ) densities were comparable with other sites. The peak densities of all hornbill species in NovemberDecember are among the highest reported from Asia. Wreathed Hornbill densities showed temporal variation peaking in NovemberDecember (68 birds/km 2 ) and drastically declining by March-April (1.3 birds/km 2 ), 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. Copyright: © Rohit Naniwadekar and Aparajita Datta. This is an open access paper. We use the Creative Commons Attribution 3.0 license http://creativecommons.org/licenses/by/3.0/us/. The license permits any user to download, print out, extract, archive, and distribute the article, so long as appropriate credit is given to the authors and source of the work. The license ensures that the published article will be as widely available as possible and that your article can be included in any scientific archive. Open Access authors retain the copyrights of their papers. Open access is a property of individual works, not necessarily journals or publishers. Given their ability to swallow and regurgitate large seeds unharmed and traverse large distances, hornbills are important dispersers of several large-seeded plants in tropical forests [4]. However, Asian hornbills are hunted for their body parts (casque and tail feathers for traditional attire), for consumption of their meat, and for their body fat, which is believed to have medicinal properties [5][6][7]. In addition, they face significant threats from logging [8,9] and habitat fragmentation [10]. Today, only a third of their natural habitat remains, a large pro...

Fruit resource tracking by hornbill species at multiple scales in a tropical forest in India

“…We recorded hornbill species, number of individuals and their arrival and departure times from the focal tree. Hornbill abundances in the study area varied across the months (Naniwadekar & Datta 2013), which could influence visitation rates on fruiting trees. For the wreathed hornbill, their densities ranged from more than 68 birds km −2 in November to around 1 bird km −2 in March (Naniwadekar & Datta 2013).…”

“…Our paper focuses on the three larger hornbill species for which we had adequate foraging observations. Hornbill densities were relatively high in the study area, although they fluctuate over time (Naniwadekar & Datta 2013). The breeding season of hornbills in the area is from April to August (Datta 2009) and our study was carried out in the non-breeding season (November–March).…”

“…We first document the diets of three sympatric hornbill species: great hornbill Buceros bicornis Linn., wreathed hornbill Rhyticeros undulatus del Hoyo & Collar and the rufous-necked hornbill Aceros nipalensis Hodgson and compare their visitation rates and visit lengths at fruiting trees. The wreathed hornbill is known to breed in low-elevation forest sites (Datta 2001, Datta & Rawat 2003) and move to mid and higher elevation forests in the non-breeding season (Naniwadekar & Datta 2013), while the great and rufous-necked hornbill do not move over elevational gradients (Datta & Rawat 2003, Datta 2009, Naniwadekar & Datta 2013). We considered resource tracking by the three hornbill species at three spatial scales: (1) at the largest scale of the study area (~15 km 2 ) where we examined temporal variation in fruit and hornbill abundance over 2 y; (2) intermediate scale: given that there could be variation in fruit availability within the 15-km 2 study area, we investigated if hornbill abundance was positively associated with fruit abundance by estimating fruit availability and hornbill encounter rates in eight systematically distributed patches of 3 ha within the 15-km 2 study area; and (3) at the smallest scale of individual fruiting trees, where we examined the relationship between fruit crop size and hornbill visitation patterns.…”

Ethnoornithological study in selected villages of Riau Province, Indonesia

“…About 95% of threatened birds around the world experience habitat loss, around 70% of which are related to human activities resulting in a decline in species populations. As discussed by Franco and Minggu (2019), there was a decline in the Helmed Hornbill population in Brunei Darussalam and also in several other countries; Philippines (Gonzales 2011), Thailand (Trisurat et al 2013), India (Naniwadekar and Datta 2013;Mudappa and Raman 2009), and Malaysia (Aik and Perumal 2017). Great pressure on bird populations by humans shows that conservation measures must involve interactions between local communities and birds in the region.…”

“…However, only about 557 species have been protected by the Government Regulation of the Minister of Environment and Forestry P.106 of 2018. The increased threat of extinction is caused by intensive illegal hunting of birds which is still rife with an increasing trend from year to the year, especially for singing birds, loss of habitat due to land-use change, and the use of pesticides (Mudappa and Raman 2009;Gonzales 2011;Trisurat et al 2013;Naniwadekar and Datta 2013;Iskandar et. al.…”