Status and distribution of endemic and threatened birds of the
Eastern Himalaya in Sikkim, India
BhojKumar Acharya 1 & Lalitha Vijayan 2
1,2 Sàlim Ali Centre for Ornithology and Natural History,Anaikatty, Coimbatore, Tamil Nadu 641108, India
Present address: 1 Department
of Zoology, Sikkim Government College, Tadong, Gangtok, Sikkim 737102, India
Email: 1 acharya2skm@gmail.com, 2 vijayanlalitha@yahoo.com
Date of
publication (online): 26 February 2010
Date of
publication (print): 26 February 2010
ISSN 0974-7907
(online) | 0974-7893 (print)
Editor: Geeta Padate
Manuscript
details:
Ms # o2257
Received 09 July
2009
Final received
26 November 2009
Finally accepted
15 December 2009
Citation: Acharya, B.K. & L. Vijayan(2010). Status and distribution of endemic and threatened
birds of the Eastern Himalaya in Sikkim, India. Journal of ThreatenedTaxa 2(2): 685-689.
Copyright: © Bhoj Kumar Acharya & Lalitha Vijayan 2010. Creative
Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium
for non-profit purposes, reproduction and distribution by providing adequate
credit to the authors and the source of publication.
Author details: Bhoj Kumar Acharyacompleted PhD from Sálim Ali Centre for Ornithology
and Natural History, Coimbatore, India in 2008. Currently he is an Assistant
Professor in Sikkim. His research
focuses pattern in diversity and distribution of birds, butterflies and plants
in the Himalayan elevation gradient. Lalitha Vijayan is Senior Principal Scientist at SACON,
Coimbatore. She has expertise on avian
biology and conservation ecology with experience of working on birds and their
habitats for the last three decades. Her
recent research focus is on community ecology of birds and conservation of
threatened birds in India.
Author
Contribution:
BKA undertook field study, analyzed data and wrote the manuscript. LV supervised BKA during filed study and
provided necessary suggestions during manuscript preparation.
Acknowledgements:This
paper forms a part of the ecological study on mammals, birds, herpetofauna and butterflies in Sikkim, funded by the
Ministry of Environment and Forests, Government of India through CISMHE,
University of Delhi. We are thankful to
the Government of Sikkim for necessary permissions, and founder Director, SACON
for providing facilities to work. We thank AjithKumar, S. Bhupathy, Basundhara,Ranjini and Nikhil for their cooperation and
suggestions, and field assistants for their support during the field work.
Abstract:
Due to their restricted distribution range and dwindling population endemic and
threatened species need considerable attention from ecologists. Sikkim is a part of the Eastern Himalayas
Endemic Bird Area that represents high concentrations of globally threatened
species. This study collected information on endemic and threatened birds of
Sikkim using point count method. The
number of species and their density at five elevation zones were
calculated. Out of 10 species endemic to
Sikkim, five were recorded during the present study. These species were restricted to one to three
habitats but densities varied among the habitats. Similarly, out of 17 threatened and 10
near-threatened species of birds that occur in Sikkim, we could observe only
three species. The results show that
these birds are rare or their occurrence is doubtful in recent years. The principal threat to birds in the state
appears to be loss of breeding habitat. Species-specific studies focusing on
population status, habitat requirements and assessment of threats are necessary
for the execution of conservation measures.
Key words: Birds, conservation, endemic, Eastern
Himalaya, Sikkim, threatened.
For Image and Tables - - click
here
Introduction
Restricted
range and threatened bird species need considerable attention from ecologists
and conservationists compared to wide ranging and common species. These species are more sensitive to
disturbance and invite immediate conservation concern (BirdLifeInternational 2001; Lei et al. 2003, 2007; Wijesinghe& Brooke 2005; Pandit et al. 2007). Information on status and distribution of
threatened and endemic birds, therefore, aids in prediction of disturbance
level and execution of conservation measures at all potential sites of their
occurrence (Stattersfield et al. 1998; Riley 2002;
Robin & Sukumar 2002).
The
Eastern Himalaya is represented by diverse habitats and has high variations in
altitude and climate. This habitat
supports a high diversity of birds and is one of the most diverse regions in
the Orient (Crosby 1996). The Eastern
Himalayan Mountain range is identified as an endemic bird area (BirdLife International 2001), which supports 22
restricted-range bird species of which 19 are endemic to the Eastern Himalayas
(Stattersfield et al. 1998; Jathar& Rahmani 2006; IUCN 2009). The region also represents one of the largest
concentrations of globally threatened birds in Asia. The principal threat to the avifauna of
Himalaya is the loss of habitat; particularly tropical lowland, sub-tropical
and temperate forests (Crosby 1996).
Sikkim
lies within the Eastern Himalaya Endemic Bird Area (Islam & Rahmani 2004). Out
of the 19 endemic bird species of the Eastern Himalaya, 10 are reported to
occur in Sikkim. It also represents a
relatively higher number of threatened bird species. Out of the 78 threatened birds of the Indian
Sub-continent, 17 (1 Endangered, 3 Critically Endangered and 13 Vulnerable)
occur in Sikkim (IUCN 2009). Similarly,
10 Near Threatenedspecies of birds are also reported from Sikkim.
Baseline
information on distribution of a few endemic and threatened birds of the
Eastern Himalaya is available (Stattersfield et al.
1998; Mauro & Vercruysse 2000; Ali & Ripley
2001; BirdLife International 2001; Acharya & Vijayan 2007). No study has been conducted to asses the status of endemic and threatened birds in
Sikkim. This paper discusses the status
and distribution of the Eastern Himalayan endemic, threatened and
near-threatened bird species in Sikkim. Conservation measures are also
highlighted in brief.
Study
area:
Sikkim (27003’-28007’N & 88003’-88057’E), a small state of India, is
situated at the western extremities of the Eastern Himalaya (Image 1). Within the 7096km2 area it has a varied
climate, topography, vegetation and altitudinal ranges. As rainfall varies from
2000-5000mm, Sikkim is considered the wettest region in the entire Himalayan
belt (Ali 1962; Mani 1974) with a relative humidity of 70-80% throughout the
year. The climate varies from hot
tropical at the lower elevations to cool temperate at the middle and arctic
cold at the higher elevations. The
altitude ranges from 300m to more than 8000m. Vegetation, which is chiefly determined by elevation and various
physical and ecological factors, changes from tropical to sub-tropical,
temperate broadleaved, mixed coniferous, sub-alpine and alpine. The alpine zone represents the typical
trans-Himalayas.
Methods
Point count method (Bibbyet al. 2000) was used along the predetermined transects for sampling
birds. On encountering a bird, details
such as species, number of individuals and the distance from the observer when
first sighted were noted. Depending upon the vegetation and elevation of the
study area, sampling sites were divided into five zones. These are - Zone I (<900m) - tropical
semi-deciduous forests; Zone II (900-1800m) - tropical moist and broad-leaved
forests; Zone III (1800-2800m) - temperate broad-leaved forests; Zone IV
(2800-3800m) - temperate coniferous and broad-leaved forests; and Zone V
(3800-4500m and above) – sub-alpine and alpine vegetation. Permanent points were established in each
transect. Points were replicated 9-12 times covering different seasons during
2003 to 2006. In addition, surveys were
also conducted covering various parts of the state.
The number of species and density of species in each
zone were estimated. Density was calculated based on Reynolds et al. (1980); D
= n*10000/ pr2C, where D = bird density (numbers/ha), n = total number of birds
observed in all counts within the specific radius, r = specific radius (m), C =
total number of counts conducted and p = 3.14. The information on altitudinal distribution was obtained from literature
(Ali 1962; Stattersfield et al. 1998; Ali &
Ripley 2001; BirdLife International 2001; Islam &Rahmani 2004) as well as field observations.
Five
endemic species, namely Chestnut-breasted Partridge Arborophila mandellii, Wedge-billed Wrenbabbler Sphenocichla humei,Rufous-throated Wrenbabbler Spelaeornis caudatus,
Ward’s Trogon Harpactes wardii and Giant Babax Babax waddelli were not observed during the course of
this study. Among these species,
Chestnut-breasted Partridge was reported to occur in habitats similar to zones
I, II and III, Rufous-throated Wrenbabblerto zone IV and Wedge-billed Wrenbabbler to zone V
(Ali 1962; Ali & Ripley 2001; Islam & Rahmani2004) but the distribution of the rest two is not known.
Similarly,
out of the 17 threatened and ten near-threatened birds of Sikkim (IUCN 2009),
only three near-threatened species (Rusty-bellied Shortwing,Firethroat and Satyr Tragopan)
were observed in Sikkim during this study. Species such as Palla’s Fish Eagle Haliaeetus leucoryphus,Black-breasted Parrotbill Paradoxornis flavirostris, and Beautiful Nuthatch Sitta formosa are
reported to have a wider distribution range but the other species such as
White-rumped Vulture Gyps bengalensis,
Long-billed Vulture Gyps indicus, Red-headed
Vulture Sarcogyps calvus,Baer’s Pochard, Aytha baeri, Greater Spotted Eagle Aquila clanga, Lesser Kestrel Falco naumanni, Blyth’s Tragopan Tragopan blythii,
Black-necked Crane Grus nigricolis,
Slender-billed Babbler Turdoides longirostris, Rufous-necked
Hornbill, Aceros nipalensis and Wood Snipe Gallinago nemoricola have merely presence-absence records in
Sikkim (Ali 1962; Ganguli-Lachungpa 1998; Ali &
Ripley 2001; Islam & Rahmani 2004).
The
result indicates that the population of these birds in Sikkim is very low. Habitat loss and fragmentation is considered
the major factor for decline in population of threatened and endemic birds in the
Himalaya and elsewhere (Crosby 1996; Mauro & Vercruysse2000; BirdLife International 2001; Chettri et al. 2001, 2005; Riley 2002; Robin & Sukumar 2002; Pandit et al.
2007). It is reported that endemic birds
are unable to utilize non-forest habitats resulting from deforestation and
conversion of land to other uses (Lei et al. 2003; Wijesinghe& Brooke 2005; Vijayan & Gokula2006). Fragmentation and loss of habitat
of the restricted range species threatens their very survival (Lei et al.
2003). The study by Pandit et al. (2007)
predicts that by the end of this century, a quarter of
the endemic species of the Himalaya will be extinct due to habitat loss.
Extinction of endemic species is primarily driven by the loss of potential
breeding habitat (Mauro & Vercruysse 2000; BirdLife International 2001).
Maximum
species of endemics and threatened birds in Sikkim are found in tropical
broadleaved forests (zone II) and temperate broadleaved forests (zone
III). The diversity of birds is also
high in these zones (Acharya 2008). Tropical and temperate broadleaved forests
are breeding ground for most of these species but human population pressures
and various ongoing developmental projects have posed serious threats to these
habitats. The forests in zone II is outside
the purview of current protected area network (Acharyaet al. 2008). Hence, conservation
through community participation would be effective for conservation of birds in
these habitats.
This
study was undertaken as a part of the bird community study in Sikkim which was
more focused to understand the distribution pattern of birds along elevation
gradient (Acharya 2008). Hence, some species might have been missed or
densities underestimated though special attention was given to endemics and
threatened birds. Long-term specific
study on these species provides better understanding of population status,
distribution and threat. Hence, detailed
study on the ecological aspects and habitat requirements is necessary for the
execution of species-specific conservation measures.
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