Occurrences of Hornbills (Bucerotidae) in the Forest Fragments of Eastern Assam
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Manuscript received on 06 October 2019. any Asian hornbill species are threatened by loss of While there is considerable information on the distribution habitat, forest fragmentation, hunting, and logging and ecology of hornbills from the fragmented forests in M(Poonswad et al. 2005). Five hornbill species, Great Western Ghats (Raman & Mudappa 2003; Pawar et al. Hornbill Buceros bicornis, Rufous-necked Hornbill Aceros 2018), information from north-eastern India is lacking. Digboi, nipalensis, Wreathed Hornbill Rhyticeros undulatus, Oriental Doomdooma, Dibrugarh, and Tinsukia forest divisions of Pied Hornbill Anthracoceros albirostris, and White-throated eastern Assam (also referred to as the Upper Brahmaputra Brown Hornbill Anorrhinus austeni, are found in north-eastern Valley) harbour some of the last remaining lowland tropical India (Datta et al. 2018). The Great-, Wreathed-, and Rufous- forests which have undergone severe fragmentation as a result necked Hornbills are classified as ‘Vulnerable’ (BirdLife of the expansion of tea plantations, coupled with agriculture, in International 2018a,b,c), the White-throated Brown Hornbill as the past century (Sharma et al. 2012). These forests now exist ‘Near Threatened’ (BirdLife International 2018d), and Oriental as a set of isolated fragments alongside two better-protected, Pied Hornbill as ‘Least Concern’ (BirdLife International 2016) large (>100 sq. km) forest patches (Jeypore Reserved Forest, under The IUCN Red List of Threatened Species. Hornbills play and Dehing Patkai Wildlife Sanctuary). While hornbills have an important ecological role as seed dispersers in tropical forests been reported from these two larger forest patches, information (Naniwadekar et al. 2019; Kitamura S. 2011). on hornbill occurrence, breeding, and diet from the smaller JAIN & SUMASHINI: Hornbills (Bucerotidae) in the forest fragments of eastern Assam 175 fragments is sparse. There were no previous records of the calling, which stopped, once they entered the canopy. We found Great Hornbill, White-throated Brown Hornbill, and Wreathed six regurgitated seeds of Dysoxylum gotadhora when we visited Hornbill occurrences in these fragments, prior to 2019, on eBird the roost at 0650 h the following day. We recorded instances (Jain 2019). Only the Oriental Pied Hornbill has been reported of Brown Hornbill feeding on fruits of Dysoxylum procerum, from one of the fragments (Bherjan Wildlife Sanctuary) in Dysoxylum gotadhora, and Horsfieldia kingii during the first week Tinsukia District (Pratim 2018). of April in Kakojan RF. On 21 April 2019, we recorded a Brown Here, we report the presence of the Great Hornbill, Wreathed Hornbill swallowing ripe fruits of Dysoxylum procerum in Doom Hornbill, and White-throated Brown Hornbill, apart from the Dooma RF. commonly found Oriental Pied Hornbill, from fragments that are At 0940 h on 05 April 2019, we encountered a female isolated from the large (>100 sq. km) Reserved Forests (hereinafter, Brown Hornbill entering a cavity in a Dipterocarpus RF) or Wildlife Sanctuaries (hereinafter, WLS). This report is a macrocarpus tree (height ~30 m) in Kakojan RF. While the synthesis of anecdotal field observations on hornbills, made during female entered the cavity, the adult male was perched next our four-month study (January–April 2019) to investigate the to the female [225]; Jain 2019). On 07 April 2019, we saw impacts of habitat fragmentation on diurnal squirrels, and plant- regurgitated seeds of Aglaia spectabilis, Polyalthia simiarum, seed disperser communities, when we periodically surveyed forest Dysoxylum procerum, Dysoxylum gotadhora, Horsfieldia fragments in this landscape. All records of hornbills have been kingii, and Chisocheton sp., under the nest tree [226a]. These uploaded to eBird (www.ebird.org/india). seeds have also been collected from under Brown Hornbill We surveyed six fragments: Kakojan RF, Doom Dooma RF, nests in Namdapha National Park in Arunachal Pradesh Borajan WLS, Bherjan WLS, Dangori RF, and Tokowani RF (Table (Datta 2009). We made sure that the birds at nest were not 1; Fig. 1), between 27.12° to 27.66°N, and 95.36° to 95.64°E. disturbed and a safe distance was maintained while making While Kakojan RF and Doom Dooma RF are about 25 sq. km, these observations. In Doom Dooma RF, we recorded a flock others are less than 10 sq. km. The fragments are separated by of Brown Hornbills inspecting a cavity in a Dipterocarpus about 06–20 km from the larger forest patches. In the medium- sized fragments (~25 sq. km), Great Hornbill, Brown Hornbill, macrocarpus tree on 21 April 2019. However, the flock was Wreathed Hornbill, and Oriental Pied Hornbill were recorded from continuously mobbed by a Hill Myna Gracula religiosa pair. Kakojan RF (Table 1), and all these species, except Wreathed This reveals that the Brown Hornbill is breeding in these Hornbill, from Doom Dooma RF (Table 1). Only the Oriental Pied fragments. Hornbills nesting in cavities of Dipterocarpus spp., Hornbill was recorded from the smaller fragments. The median has previously been documented from South-east Asian (range) number of individuals in sightings of Great Hornbill were tropical forests (Poonswad 1995). 1 (1–2), that of Brown Hornbill were 5 (1–11), and Oriental Pied Hornbill were 2 (1–4).