Comparison of avifaunal diversity in and around Neora
Valley National Park, West Bengal, India
Utpal
Singha Roy 1, Arijit Pal 2, Purbasha Banerjee 3& Subhra Kumar Mukhopadhyay 4
1 Department
of Zoology, 2,3 Department of Conservation Biology, Durgapur
Government College, JN Avenue, Durgapur, West Bengal 713214, India
4 Hooghly
Mohsin College, Chinsurah, West Bengal 712101, India
Email: 1 srutpal@gmail.com
(corresponding author), 2 arijitpal1988@gmail.com, 3 banerjeepurbasha@gmail.com, 4 msubhro@yahoo.com
Date of
publication (online): 26 October 2011
Date of
publication (print): 26 October 2011
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: Rajiv S.
Kalsi
Manuscript details:
Ms # o2542
Received 11 August 2010
Final received 28 August 2011
Finally accepted 27 September 2011
Citation: Roy, U.S.,
A. Pal, P. Banerjee & S.K. Mukhopadhyay (2011). Comparison of avifaunal diversity in and around Neora Valley
National Park, West Bengal, India. Journal of Threatened Taxa 3(10): 2136–2142.
Copyright: © Utpal
Singha Roy, Arijit Pal, Purbasha Banerjee, Subhra Kumar Mukhopadhyay 2011. 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.
Acknowledgements: The authors
are thankful to the Director of Public Instuction, Government of West Bengal
and Divisional Forest Manager, Kalimpong, West Bengal for their kind help and
cooperation.
Abstract: Anthropogenic
intervention has led to conversion of much of the global diversity by means of
habitat alterations. The present
study was carried out to investigate the importance of habitat quality and
habitat heterogeneity for the diversity, distribution and abundance of avifauna
in and around Neora Valley National Park (NVNP) during April–May
2010. A total of 73 bird species
belonging to 25 families were recorded during the present study applying a
modified point count method. Forest edges were found to be most diverse with a total count of 54 bird
species having an abundance of 172.53 number of birds ha-1. Study areas with human settlements was
represented by a total species count of 24 with an abundance of 130.39 number
of birds ha-1 while a total species count of 22 with an abundance of
69.32 number of birds ha-1 was recorded from thick vegetation
assemblage with close canopy cover. This site specificoccurrence pattern for avifauna was reflected in the study of diversity
indices. The highest Shannon-Wiener
general diversity score of 3.77 was recorded for bird species from forest
edges. Study areas with dense
canopy closure were found to support more habitat specialist bird species while
areas having human settlements harboured more opportunistic bird species. An overall negative influence of human
settlements on bird diversity, distribution and abundance was evidenced from
the present study and needs further investigation. Moreover, intensive studies will certainly enrich our
knowledge of avian diversity and distribution pattern from the present study
location.
Keywords: Avifauna,
diversity indices, hotspot, Lava, Neora Valley National Park.
For figures, images, tables -- click
here
Neora
Valley National Park (NVNP), is a compact patch of virgin forest located in the
Eastern Himalaya, is a global ‘Biodiversity
Hotspot’. The northern and northeastern boundaries of NVNP are contiguous with
Sikkim and Bhutan, respectively, and link the Pangolakha Wildlife Sanctuary in
Sikkim. The southern boundaries of
NVNP are remotely connected with the Chapramari Wildlife Sanctuary and the
Gorumara National Park. NVNP
belongs to an Important Bird Area (IBA Site code: IN-WB-06 under the IBA
criteria: A1 (threatened species), A2 (endemic bird area) and 130: Eastern
Himalaya. According to Islam &
Rahmani (2004), Prakriti Samsad has recorded 288 species of birds from Lava and
Loleygoan ranges which are adjacent to this National Park. Relationship between
habitat and bird diversity has been reported by Chettri et al. (2005)
from western Sikkim. The present
study attempts to prepare a checklist of birds to compare bird diversity of
closed canopy covered areas of NVNP, its edges and of the areas where forests
are subjected to various degrees of pressure from human disturbances.
Study
Area
Three
contrasting forest patches were chosen in the present study depending upon the
complexity of habitat structure. A
thick vegetation assemblage with close canopy cover, edges of forests, and
areas with human settlements in and around NVNP were studied for bird diversity
and has been referred to as study area 1 - (27005’49”N &
88041’29”E; 1927m), study area - 2 (27006’01”N & 88040’33”E;
1612m) and study area - 3 (27005’11”N & 88039’41”E;
2061m) in the present investigation (Image 1). Study area - 3 was located adjacent to a hill station Lava,
a place of major tourist attraction in northern Bengal. Intense anthropogenic influence, both
direct and indirect was evident in this area. Much of the forest has already been destroyed here and ever
increasing tourism pressure is engulfing the remains.
Neora
Valley was notified as a national park in the year 1992 based on the provisions
of the Wildlife (Protection) Act 1972 and covers two biomes, the Sino-Himalayan
temperate forest (Biome-7) from 1800 to 3600 m elevation and the Sino-Himalayan
subtropical forest (Biome-8) from 1000 to 2000 m elevation (Islam & Rahmani
2004). The phytogeography of NVNP
consists of the subtropical broadleaf hill forest, montane wet temperate forest
and subtropical pine forest (Champion & Seth 1968). According to Rodgers et al. (2002) NVNP
lies in the bio-geographic zone 2. Floral and faunal composition of NVNP typically represents that of oriental
regions with high endemism. Human
settlements around this protected area have altered the biodiversity due to
habitat degradation. This region
is a major tourist attraction and the consequent disturbances coupled with the
pressure for livelihood of local people is forcing the conversion of this well
known birders’ paradise.
Methods
Sutherland
(2006) recommended point count as the most efficient method for estimating
avian abundance from mixed habitat types. Since the present study site was mostly heterogeneous, a total of 162 point counts (nine counts on each day for six
consecutive days at three sites) during the first two hours after sunrise (0600–0800
hr), during noon (1100–1300 hr) and in the evening (1600–1800 hr)
between the 29 April and 04 May 2010 were carried out. We selected a grid of nine points in
each study site and adjacent points were 200m apart. Counting of birds in bands of 30 and 50 m has been
recommended for close forest and open habitat areas (Sutherland 2006). In the present study a fixed radius
(always at a distance between 30 and 40 m) circular-plot method was used. At each individual point count,
observations were made for 10 minutes for all the birds seen (perched or flying
under the canopy) and photographed if not identified immediately. Birds seen or heard within the fixed
radius plot were counted separately from those detected outside the plot. Ali (1996), Grimmett et al. (1998) and
Kazmierczak & Perlo (2000) were followed for identification. Avifaunal density was calculated by
applying the formula: Avifaunal density, Ď = (n1 + n2/π r2m) ln (n1 + n2/n2) (where, r =
radius of concentric zone from the point of observation (30 and 40 m); n1= number of birds counted within r; n2 = number of birds counted
beyond r; m = number of replicate counts) following Henderson (2003). Shannon-Wiener index of diversity (H/),
Pielou’s evenness index (J/), Margalef’s richness index (DMARG)
and Simpson’s dominance index (DSIMP) were calculated to analyze the
avian community structure using PAST statistical software (Pandya &
Vachhrajani 2010). Although both
Shannon measures and Simpson’s index consider the proportional abundances of
species, H/ is more sensitive to rare species, whereas DSIMPputs greater emphasis on common species. On the other hand, Margalef’s richness index (DMARG),
considers both abundances and species numbers whereas Pielou’s evenness index
(J/) considers abundance and species occurrence pattern. Therefore, combinations of these
indices were used to comment on the diversity of avifaunal community from the
present study locations. Hierarchical cluster analysis was done to construct a dendrogram for
commenting on the relation between the study areas, using SPSS 13.0.
Results
A
total of 73 bird species belonging to 25 families were recorded during the
short period of the present study (Appendix 1). Family-wise distribution of all the bird species varied
widely among all three study sites, with Muscicapidae
having the highest representatives followed by Corvidae. The highest bird diversity was recorded
in study area - 2 (total species count of 54 with an abundance of 172.53 birds
ha-1) followed by study area - 1 (total species count of 24 with an
abundance of 130.39 birds ha-1) and study area - 3 (total species
count of 22 with an abundance of 69.32 birds ha-1). Figure 1 represents the co-occurrence
of birds among the three study sites. The transition zones between study area - 1 and study area - 2, study
area - 2 and study area - 3 and study area - 1 and study area - 3 were
represented by 17, nine and five bird species, respectively. Only five bird species were found at
the same time in all three sites. All the diversity indices studied in the present investigation were
higher in study area - 2 with H/, DSIMP, J/ and
DMARG scores of 3.77, 0.97, 0.80 and 10.29 respectively (Table
1). Diversity index values
recorded from study area - 1 and study area -3 werecomparable with H/, DSIMP, J/ and DMARG scores
of 2.64 and 2.86, 0.90 and 0.93, 0.58 and 0.80 and 4.72 and 4.95,
respectively. Dendrogram,
constructed from hierarchical cluster analysis showed that study area - 1 and
study area - 3 were nearer to each other while the most diverse forest edges of
study area - 2 was the farthest (Fig. 2).
Discussion
Conservationists
around the globe are facing great challenges under the mounting threats of
anthropogenic disturbances to biodiversity. Moreover, holistic inventory of diversity requires nearly
impossible levels of time and effort. Considering these factors, short-span study of biota for overall
biodiversity estimation is of great importance and of late much emphasis has
been given to prepare checklists of birds on a wider scale (Chakravarthy &
Sridhar 1995).
This
study indicated a greater diversity of birds in forest edges when compared to
dense forest patches with closed canopy covers and in areas with anthropogenic
settlements and these finding is similar to Aich & Mukhopadhyay (2008). Edges of forests were found to contain
both habitat generalist and habit specialist birds while dense canopy closure
supported more of habitat specialist avian species like, Spot-bellied Eagle OwlBubo nipalensiswhile areas under anthropogenic influence harboured more of opportunistic bird
species. Distribution wise, only
five bird species were found to be co-occurring in all three
study sites. This habitat
specific distribution of avifauna was reflected in the study of diversity
indices where all the indices were higher in areas of forest edges. Avifaunal diversity and abundance in
canopy closure were higher than in areas with human settlements but diversity
index scores of both the study areas were comparable. This was also reflected in the dendrogram where the most
diverse forest edges (study area - 2) were located separately from the cluster
of study area - 1 and study area - 3. This may be attributed to the fact that although both Shannon measures
(H/) and Simpson’s index (DSIMP) consider the
proportional abundance of species, H/ is more sensitive to rare
species, whereas DSIMP puts emphasis on the common species. Species evenness in homogeneous forest
edges was higher, and was followed by areas under anthropogenic influence and
closed canopy cover. This may be
due to the fact that canopy closure supports more specialist species with
restricted distribution pattern and narrow niche width while areas under
anthropogenic intervention support even distribution of generalist and
opportunistic bird species that can exploit the available resources with an
overlapping pattern of niche width. Anthropogenic disturbances on forest structure and function are well on
record (Bhat & Murali 2001; Chandrashekara et al. 2006) and present
findings also indicated a negative influence of anthropogenic intervention on
overall bird diversity.
The
present investigation recorded one globally vulnerable species, the Beautiful
Nuthatch Sitta formosa. This species has been referred to as Vulnerable[C2a(i)] by BirdLife International (2010) IUCN Red List (2011) for birds, due to its
small, declining and highly fragmented population size. Conservation measures have been taken
for this species in adjacently located Buxa Tiger Reserve and we would like to
propose NVNP to be designated for the same cause. We would also like to mention that the current investigation
included a vagrant bird, Water Pipit Anthus spinoletta, anew record from this part of the world.
Our
short-term study involved only a few selected patches of forests; a more
intensive study might yield many more species. Detailed studies might improve the list of avian species and
their characteristic distribution in different forest patches from the present
location. The impact of
anthropogenic alteration of the habitats in and around Neora Valley National
Park also needs further intensive studies.
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