Avifaunal diversity of Tsirang District with a new country record for Bhutan

: Birds play a vital role in ecosystems. Studying avifaunal diversity therefore has a noteworthy role in indicating nature’s ecological balance in the environment. A total of 749 bird species have so far been recorded in Bhutan. We present a comprehensive checklist of birds of Tsirang, District which largely lies outside Bhutan’s protected area system. The data was collected through opportunistic encounters and with regular field visits to a range of locations in different seasons. One-fourth of the country’s total avifauna and a new species recorded for Bhutan, The Plum-headed Parakeet Psittacula cyanocephala was recorded as part of this study. In all, 285 avian species belonging to 18 orders and 65 families including one globally ‘Critically Endangered’, three ‘Vulnerable’, and a ‘Near Threatened’ species were recorded during the survey. The high species richness of birds in the study area reveals that it includes good habitats for birds in Bhutan. Similar studies are suggested in other areas contiguous to the protected areas in Bhutan including the current study area. This should aid in understanding of the factors driving the differences in bird diversity within and outside the protected areas so as to facilitate informed conservation actions in future.


INTRODUCTION
Described as 'feathered bipeds', birds are a very visible and integral part of the ecosystem (Ali 1941).Their roles include ecological health indicators, plant pollinators, and seed dispersers as well as pest regulators (Ali 1941;Bilgrami 1995;Harisha & Hosetti 2009).
It is said that the bird exploration in Bhutan began as early as 1937 by a team of foreigners from Britain (Ludlow & Kinnear 1937;Clements 1992;Gyeltshen et al. 2020).Since then, a number of studies on birds have been carried out in Bhutan which have contributed to developing baseline data.For example, Inskipp & Inskipp (1993) recorded 319 bird species, including 21 previously unpublished records for Bhutan.
The first detailed and comprehensive field guide titled 'Birds of Bhutan' recorded 616 species (Inskipp et al 1999).After two decades, the same team with an additional author from Bhutan published a new book titled 'Birds of Bhutan and the Eastern Himalayas', which is one of the latest comprehensive works on avifauna for Bhutan.According to Grimmett et al. (2019), Bhutan hosts 736 bird species.Since then, the Bhutan Birdlife Society (BBS) which is one of the latest civil society organizations (CSO) has shown through its Facebook group that 748 species have been recorded in Bhutan.The increase in the number of new records is attributed to a citizen science initiative as confirmed by ornithologists Tim Inskipp & Sherab (as cited in Dendup et al. 2020;Gyeltshen et al. 2020).With the recent sighting of Short-tailed Shearwater Adenna tenuirostris from Phibsoo Wildlife Sanctuary on 20 January 2021, a total of 749 species has been recorded in Bhutan (BBS 2021).
Bhutan is one of the Endemic Bird Areas (EBA) in the eastern Himalaya (Stattersfield et al. 1998;Bishop 1999).This is attributed to suitable climatic conditions, and the availability of natural resources in the region (Mohammad & Krishna 2016).
Bhutan has made a great effort to protect birds and their habitat.For example, the Biodiversity Conservation Act 2003 and Forest and Nature Conservation Rules and Regulations 2017 cover bird conservation, and 36 species (National Biodiversity Centre 2019) are listed as totally protected under schedule I.

Study Area
Tsirang Forest Division jurisdiction is located in the south-central part of Bhutan (Figure 1).The total area of Tsirang is 638.8 km 2 and it is located between 27 o 11'58.6"N -27 o 48'59.9"N and 90 o 20' 57.7" E-90 o 20'23.3"E in central Bhutan.Tsirang shares boundaries with three other districts: Wangdue Phodrang, Dagana, and Sarpang in central Bhutan.Tsirang has 12 blocks and 101 villages with a population density of 35.9 per km 2 (Tsirang 2021).
The vegetation in the district is predominantly broadleaved forest covering 77.64% of the land area.In addition, there are other forest types such as Chir Pine Pinus roxburghii forest covering 6.51%, fir Abies forest covering 0.40%, and mixed conifer forests covering about 2.95% at the outer reaches of the district (FRMD 2017).The other significant vegetation is shrubs at 3.30%, which make up the higher altitude mountain slopes to the north of the district. A

Methods
The data was gathered through intentional and opportunistic records in most parts of the district to document avifaunal diversity with most of the records captured during our field visits.The areas covered are located at altitudes ranging 250-2,500 m.Bird watching was normally done in the early hours (0600-0900 h) and occasionally in the evening at around 1530-1800 h.This survey explored a wide range of habitats including forests, streams, artificial ponds, and cultivation to study bird diversity.Canon 1300D, Canon Rebel T5, Nikon D5100 DSLR cameras with a zoom lens of max 300 mm, and 8x42 binoculars were used for bird watching and to capture bird images.
Birds were identified to the species level with the help of various available field guides (Grimmett et al. 1999(Grimmett et al. , 2019) ) and experts' identification through the Birds of Bhutan (Bhutan Birdlife Society) Facebook forum.The terminology is based on Manakadan & Pittie (2001).
The birds were categorized as A-Abundant (sighted

RESULTS AND DISCUSSION
A total of 258 avian species belonging to 18 orders and 65 families was recorded (Table 1).The bird species were categorized by their order, abundance, and conservation status.
Among the total of 18 orders, Passeriformes was the dominant order comprising 71.3% (184 species in 45 families) of the total species recorded, followed by

J TT
Piciformes (13 species in 2 families) with 5.03% of the total species count.Trogoniformes, Caprimulgiformes, Suliformes, and Psittaciformes were the least represented orders with a single species each (Figure 2).
The majority of bird species fall in the occasional group (O) with 51.5% (n = 133) of the total species recorded, followed by Common bird species (C) with 25.5% (n = 66) of the total, abundant species with 7.36% (n = 19) of the total and rarely sighted species with 7.4% (n = 19) of the total species recorded.
The results reported by Gyeltshen et al. (2020) in Trongsa District in central Bhutan also indicated that passerines were the most dominant order in which our result was consistent with Gyeltshen et al. (2020).The majority of bird recorded (253 species, 98% of the total) have been assessed as Least Concern (LC).Four globally threatened species were also sighted during the survey (Figure 4).Amongst the rarely sighted species is the globally 'Critically Endangered' White-bellied Heron Ardea insignis which occurs at 250 m along the Sankosh River, one of the longest rivers in the country, and its tributaries.

CONCLUSION AND RECOMMENDATIONS
This study represents one of the few documented references of bird inventory in the region and can be used as baseline data for future monitoring and survey.The comprehensive bird checklist indicates, that some areas lying outside protected areas in Bhutan provide good habitats for birds.However, the current trend of anthropogenic activities such as timber felling, new farm road construction, and increased resource collections due to fewer restrictions as opposed to within protected areas pose a significant threat to birds.
Since this study was limited to a checklist, there are opportunities for in-depth studies on birds' interaction with ecosystems and associated threats in order to encourage bird conservation in the area.Further, a systematic study is recommended covering the whole of the Tsirang Forest area jurisdiction as we could only portion of Tsirang District in the north lies in Jigme Singye Wangchuck National Park (JSWNP) covering about 34 km 2 in Sergithang block and Phuntenchu block.Part of southeastern Tsirang lies in the biological corridor network which connects JSWNP, Royal Manas National Park (RMNP), and Phibsoo Wildlife Sanctuary (PWS).With a warm and temperate climate, the elevation of Tsirang ranges 200-4,500 m (FRMD 2017).It is inhabited by rural settlements distributed sparsely on the hills and gentle slopes.
Journal of Threatened Taxa | www.threatenedtaxa.org| 26 August 2023 | 15(8): 23681-23695 23683 J TT almost every time we go for bird watching in different sites); C-Common (sighted 10 times in the region); O-Occasional (sighted occasionally up to 5 times); and R-Rare (once or twice) based on the presence or absence during our visit to the areas.

Figure 1 .
Figure 1.Study area where bird species were observed.
The globally 'Vulnerable' Rufous-necked Hornbill Aceros nipalensis and Great Hornbill Buceros bicornis were recorded from different localities including Barshong, Sergithang, Patshaling, Phuentenchu, and Mendrelgang during the survey.The Beautiful Nuthatch (VU) Sitta formosa was recorded from the Daratsho area adjoining Sarpang district which lies in the biological corridor that connects JSWNP, RMNP, and PWS.The globally 'Near Threatened' species River Lapwing Vanellus duvaucelii was also recorded from the lowest altitude of Sunkosh River and Malbasay under Patshaling block.A single male Tibetan Serin Serinus thibetanus was observed once at Patshaling Block in February 2017 by the roadside and the Sapphire Flycatcher Ficedula sapphira the following day at Mendrelgang block.Neither species was sighted subsequently despite consistent efforts to find them.Common Myna Acridotheres tristis, Rock Pigeon Columba livia, Eurasian Tree Sparrow Passer montanus, and White-crested Laughing thrush Garrulax leucolophus are abundant in the locality.The Plumheaded Parakeet Psittacula cyanocephala (Image 65) is a new record contributed to the list of Birds of Bhutan sighted first on 28 October 2018 at Mendrelgang block under Tsirang District at 2,100 m by the first author.The record was later verified and confirmed by Tim Inskipp & Sherab.Most of the birds were observed and photographed at the edges of cultivation, along highways, on farms, and on roadsides.Many of these birds were recorded during the spring and autumn seasons.

Figure 2 .
Figure 2. Number of bird species by order.