Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 September 2020 | 12(14): 16927–16943
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
doi: https://doi.org/10.11609/jott.5815.12.14.16927-16943
#5815 | Received 26 February 2020 | Final
received 17 September 2020 | Finally accepted 20 September 2020
Elevational pattern and
seasonality of avian diversity in Kaligandaki River
Basin, central Himalaya
Juna Neupane
1, Laxman Khanal 2, Basant Gyawali 3 & Mukesh
Kumar Chalise 4
1,2,3,4 Central Department of Zoology,
Institute of Science and Technology, Tribhuvan University, Kathmandu 44613,
Nepal.
2,4 Nepal Biodiversity Research
Society (NEBORS), Lalitpur, Nepal.
1 zunaneupane@gmail.com, 2 lkhanal@cdztu.edu.np
(corresponding author), 3 basantgyawali1@gmail.com, 4
mukesh57@hotmail.com
Abstract: This study explored bird
diversity, seasonal variation, and associated factors along an elevational
gradient in an important biodiversity area (IBA) of central Nepal: the Kaligandaki River basin of Annapurna Conservation
Area. The field survey was carried out
in 2019 over two seasons, winter (January and February) and summer (May and
June) using the point count method. A
total of 90 sampling plots were set up from elevations of 800m (Beni) to 3,800m
(Muktinath).
Data for variables including the number of fruiting trees (indicator of
resource availability) and distance to the road (indicator of disturbance) were
collected, and their influence on avian diversity were assessed. The results revealed a diverse assemblage of
avian fauna in the study area with consistent species richness over the two
seasons. A decline in species richness
and diversity with increasing elevation was observed. Of the different habitat types within the
study area, forest and shrubland habitats showed the strongest association with
bird species distribution and richness.
We emphasize the need for long-term monitoring programs with
standardized sampling approaches to better understand the avifauna in the
central Himalaya.
Keywords: Biodiversity pattern,
birds, elevational gradient, monotonic decline, species richness.
Editor: Carol Inskipp, Bishop Auckland Co., Durham, UK. Date of
publication: 26 September 2020 (online & print)
Citation: Neupane, J., L. Khanal, B. Gyawali & M.K. Chalise (2020). Elevational
pattern and seasonality of avian diversity in Kaligandaki
River Basin, central Himalaya. Journal
of Threatened Taxa 12(14): 16927–16943. https://doi.org/10.11609/jott.5815.12.14.16927-16943
Copyright: © Neupane et al. 2020. Creative
Commons Attribution 4.0 International License.
JoTT allows unrestricted use, reproduction,
and distribution of this article in any medium by providing adequate credit to
the author(s) and the source of publication.
Funding: This study
was supported by a student research grant under the Hariyo
Ban program of WWF Nepal (GX70, AID-367-A-16-00008).
Competing interests: The authors declare no competing interests.
Author details: Juna Neupane, MSc, is a 2019 graduate in zoology and her research
interests include avian fauna (roles that spatial patterns and processes play
in shaping avian communities), primatology and behavioral
studies. Laxman
Khanal’s
research interests include biodiversity exploration, phylogeny and phylogeography of mammals, molecular ecology and
conservation ecology. Basant Gyawali’s
research interests include wildlife conservation, general ecology (mammals) and
bird communities. Mukesh Kumar Chalise
is a pioneer primatologist and renowned wildlife biologist in Nepal and has
also worked as visiting professor in Kyoto University, Japan and Dali
University, Yunnan, China.
Author contribution: JN, LK and MKC conceptualized the project. JN carried out the field work. JN, LK and BG analyzed the data and prepared
the manuscript. MKC supervised the
overall research and contributed in the manuscript improvement.
Acknowledgements: We acknowledge support from the Central Department of
Zoology, Tribhuvan University and Hariyo Ban program
of the WWF Nepal. We are also thankful
to the Department of National Parks and Wildlife Conservation, Ministry of
Forest and Soil Conservation, District Forest Office, Myagdi
and Unit Conservation Offices, Ghandruk and Jomsom for research permission and assistance. We thank Mr. Gopal Khanal,
Assistant Conservation Officer, DNPWC and field assistants for their support.
Patterns in the diversity and composition of species
along elevation gradients are key issues in ecology (Lomolino
2001) that contribute to understanding global biodiversity (McCain 2009). The spatial and temporal aspects of
species variation along such gradients provide clues to understanding
mechanisms of species richness and diversity, a key challenge for ecologists
and conservationists (Gaston et al. 2000).
Global latitudinal diversity, a well-known pattern where species
richness peaks in the tropics and drops towards the poles, has been extensively
explored (Rosenzweig 1992; Hillebrand 2004; Pigot et
al. 2016). While elevation gradients have not been studied as expansively, they
also present prominent patterns in diversity (McCain 2010).
Many studies have demonstrated elevation-related
patterns in diversity and have attempted to describe underlying mechanisms, but
these aspects remain under debate (Sanders & Rahbek
2012; Quintero & Jetz 2018). In general, species richness has been
reported to follow one of the four main diversity patterns: decreasing with
elevation, low plateau, low plateau with a mid-elevation peak, and
mid-elevation peaks. Of these,
mid-elevation peaks are the mostly observed patterns among vertebrates (Colwell
& Lees 2000; Bertuzzo et al. 2016; Chen et al.
2017; Pandey et al. 2020). These
patterns can be explained by drivers that can be both spatial (area, mid domain
effect) and environmental (temperature, precipitation, productivity, and
habitat heterogeneity) (Colwell et al. 2004; Wu et al. 2013; Chen et al. 2017,
2020; Pandey et al. 2020). Numerous
hypotheses have been proposed to explain relationships between species richness
and altitude, such as species-area relationships, mid-domain effects,
climate-richness relationships, and productivity-richness relationships (Rahbek 1995; Grytnes & Vetaas 2002).
Variations in species richness of birds with elevation
are among the most commonly considered aspects of bird community structure
(Stevens 1992), because elevation affects the condition of the physical
environment and the types and amount of resources available for breeding and
foraging activities. Thus, the
composition and structure of bird communities may change along these gradients
(Rahbek 2005; McCain 2009). As the elevation increases, availability of
resources for birds changes with differences in forest stand structure, site
productivity, vegetation species composition, and available land area (Rahbek 2005).
Seasons also play a significant role in determining food and cover
availability, influencing reproductive success and survival of bird species (Mengesha & Bekele 2008). The seasonal variability in the measure of
precipitation and temperature and other conditions of spatial and temporal
microhabitat are prime factors influencing resource accessibility for birds. Such distributions of food and cover
resources determine the richness, abundance and habitat use of bird species
(Waterhouse et al. 2002).
Mountains provide an extensive range of environmental
factors, many of which vary with elevation (Becker et al. 2007). They often harbor a large number of species, including varied
avifauna, presenting ideal situations for exploring variation in species
diversity over relatively short distances (Korner 2007; Quintero & Jetz 2018). Many mountain areas are also global
biodiversity hotspots for bird species (Renner 2011; Inskipp
et al. 2013, 2016). Understanding the association between species richness and
elevation gradients can support conservation efforts (Stevens 1992; Raman et
al. 2005; Acharya et al. 2011).
The Kaligandaki River basin
in the Annapurna Conservation Area (ACA) of central Nepal is a major tributary
of the Ganges River basin, with a marked topographic variation originating at
the border with Tibet at an elevation of 6,268m at the Nhubine
Himal Glacier.
The ACA is one of the Important Bird and Biodiversity Areas (IBA) of the
central Himalayan region (BCN 2019). The
Kaligandaki Valley is a migration corridor for birds
moving south to India in winter. Around 40 species have been recorded moving
along the valley, including Demoiselle Crane Grus virgo
and several raptors (Inskipp & Inskipp 2003) including Steppe Eagles Aquila nipalensis, which migrate west through the ACA just
south of the main Himalayan chain (de Roder
1989). The upper section of the Kaligandaki corridor, a road connecting Indian border in the
south to the Chinese border in the north spanning along the Kaligandaki
River axis, has heavily modified the pristine landscape of the ACA. A checklist for overall bird species of the
ACA has been published (Inskipp & Inskipp 2003; Baral 2018; Neupane et al. 2020), but studies focusing on bird
diversity, seasonal variation, elevation and associated factors have not been
conducted. This study was carried out
along Kaligandaki River basin in order to explore: i) avian diversity; ii) seasonal variation in species
richness and diversity; iii) environmental factors (elevation, habitat types,
number of fruiting trees and distance to the road) affecting avian species
richness; and, iv) habitat association of different feeding guilds.
MATERIALS AND METHODS
This study was conducted in Kaligandaki
River basin within Annapurna Conservation Area (Fig. 1). The Kaligandaki
River basin is an important sub-basin of Narayani
Basin in Nepal located between 27.716– 29.316 0N and 82.883–84.433 0E.
The area has marked topographic variation with elevation varying from 183–8,143
m. The upper ridges of the Kaligandaki River Basin are characterized by high altitude,
low temperature, some glacier coverage, and dry climate with strong winds and
intense sunlight receiving less than 300mm annual rainfall. Permanent snow covers about 33% of the basin,
while over 50% of this snow cover occurs above 5,200m (Mishra et al.
2014). The middle region of the basin is
mostly hilly with high altitude terrain; the plains in the south have a
sub-tropical climate and high precipitation.
The study area covered an elevation range of 800m (Beni, Myagdi District) to 3,800m (Muktinath,
Mustang District) from sub-tropical to sub-alpine habitats for diverse avian
fauna.
At the lowest elevations of the study area, there are
subtropical forests of broadleaved Needle-wood Tree Schima
wallichii, Indian Chestnut Castanopsis
indica, with scattered Chir
Pine Pinus roxburghii on dry slopes and
Nepalese Alder Alnus nepalensis
alongside rivers and streams. The
temperate forests of mixed broadleaves and oaks Quercus lamellosa,
Q. lanata, and Q. semecarpifolia
with Rhododendrons Rhododendron spp. occupy the higher regions. Coniferous forests, mainly of Fir Abies spectabilis,
Blue Pine Pinus wallichiana grow on the
dry ridges and slopes. Above the temperate zone lie the subalpine forests of
Birch Betula utilis, Blue Pine Pinus wallichiana, and junipers Juniperus
spp.
The point count method was used to count the number of
birds in the study area. This method is
used mostly in avian fauna to estimate population densities, define population
trends, and assess habitat preferences.
It is undertaken from a fixed location for a fixed time, and can be
conducted at any time of the year (Sutherland 2006). Birds were recorded from 800–3,800 m within
two districts of Annapurna Conservation Area, Myagdi,
and Mustang along Kaligandaki River basin. The plots were set up with every 100m-rise in
elevation, which was recorded using Garmin Etrex 10
GPS. Three fixed-point count plots were
set up at each elevational plot, one on the roadside and two on either side of
the road about 250–350 m apart considering the site accessibility along the
river basin. A total of 90 sampling
plots were set up on 30 elevational points within the study area. At each plot, birds were recorded within a
circle of 30m radius from the fixed point in a center,
for 15min. The birds were observed
directly using binoculars and photographs were taken whenever possible. For taxonomic identification, the field guide
book Birds of Nepal (Grimmett et al. 2016) was
used. Birds were observed in the plot
from 06.00–11.00 h and 15.00–17.00 h. Data were collected in two seasons of
2019 – winter (January and February) and summer (May and June).
Call count method was also employed in the same point
count locations to record all the birds seen as well as heard. This method helped for the identification of
some birds that produced easily identifiable sounds that are familiar to the
researchers. This approach is used for
recording birds, which are difficult to see or capture in their preferred
habitat. Those species which are shy and
cryptic can be rarely observed even in open habitat. Similarly, in the dense habitat, it is
impossible to observe the birds in the distance. Thus, the call count method is the approach
of listening to the sound and noise produced by the birds and recording them.
Observed bird species were categorized into five
feeding guilds based on the field guide book Birds of Nepal (Grimmett et al. 2016) and following the literature (Katuwal et al. 2018): insectivores (feeding predominantly
on insects, larva, worms, spiders, crustaceans, and mollusks),
omnivores (feeding on both plants and animals), frugivores (feeding on fruits,
berries, figs, drupes, and nectars), carnivores (feeding on fishes, amphibians,
reptiles, birds, and mammals), and granivores
(feeding on seeds, grains, and acorns).
Habitats in 90 different point count sites were
categorized into seven types as forest, riverbank, agricultural area,
shrubland, grassland, scrubland and barren area. The GPS coordinates were overlaid in the
land-cover map of ICIMOD (2010) for habitat categorization. As a proxy of resource availability for
species richness and diversity, the number of fruiting trees was counted in
each sampling site within the circular plot of 30m radius. Another predictor variable, distance to the
road from the three-point count locations was taken as a proxy of human
disturbance within the study area. These
point count locations were set up in the road and either sides away from the
road about 250–350 m apart in the river basin along elevational gradient. Distance to the nearest road for each
sampling point was estimated in the field and confirmed in Google Earth (https://earth.google.com/web).
The alpha (α) diversity of bird species of the study
area during seasons and across point count stations was measured as the species
diversity index (H’) by using the Shannon-Wiener Function (Shannon & Weaver
1949). Species richness gives the
presence of the total number of species at a particular area, and it was
calculated as the total number of species recorded. The abundance of each species was calculated
as the frequency of occurrence in each plot.
To calculate whether the species were evenly distributed among the
different point count stations and the different seasons, the evenness index
(E) was used. It was calculated as
H’
E = –––––
H’max
where,
H’ = Shannon-Wiener diversity
index
H’max = maximum possible value of H’,
if every species is equally likely and equal to ln(S)
S = species richness, the total number of species
Sorenson’s similarity index (SSI) was used for the
qualitative data (presence/absence) to find the community similarity between
the two study seasons. The Sorenson’s
Index of similarity was calculated as:
2C
SSI = –––––––– x 100%
A +B
where,
C = Common number of species shared by two communities
(two seasons)
A = Number of species found in one community (one
season)
B = Number of species found in another community
(another season)
One-way ANOVA was used to test the significant
variation in species richness of birds among point count stations in two
seasons assuming the following null hypothesis- H0 = there is no
significant variation in species richness of birds between summer and winter
seasons.
The generalized linear model was used to assess how
the bird species richness and diversity change along the elevation gradient as
well as to assess the influence of resource availability (number of fruiting
trees) and human disturbance (distance to the road) on species diversity and
richness. Predictor variables included
elevation (measured in m at the centroid of 30m circular radius), resource
availability (number of the fruiting tree within 30m radius) and human
disturbance (distance from the nearest road).
Plausible generalized linear models (GLMs) with Poisson error
distribution and log link function was run as it is a powerful tool for analyzing count data for species richness in ecology. To assess the influence of predictor
variables on species diversity, multiple linear regression was used since the
response variable was continuous. Six
priori set of models, including the null model, were defined. The models were
then ranked using the corrected Akaike Information Criterion that is adjusted
for small samples (AICc) (Burnham & Anderson
2002). The beta-coefficient (slope) of
covariates was examined to test the significance of their effect on the response
variable (species richness and species diversity). All analyses were carried out using ‘Stats
Package’ in R 3.1.2 (R Core Team 2013).
The relationship of bird species richness and
environmental factors were explored using Canoco
v.4.56. A unimodal direct gradient
analysis of partial canonical correspondence analysis (CCA) was used to relate
the variation of bird communities (species richness) to habitat variables. Different habitat types were put in the
matrix of independent environmental factors whereas, recorded bird species were
grouped in the data matrix of dependent variables. Under the reduced model of the canonical
axes, Monte Carlo permutation tests (499 permutations) were used to assess the
statistical significance of the association between bird species composition
and habitat variables.
A total of 1,036 individuals of 120 bird species from
33 families of eight orders were recorded by point count method in the Kaligandaki River basin (Annex I). Out of the eight orders, order Passeriformes
had the highest species richness (98 species) and family Muscicapidae
had the highest number of bird species (17 species). Guild structure analysis revealed that half
of the total bird species were insectivores followed by omnivores, frugivores, granivores and carnivores (Fig. 2). Out of the 120 species recorded from the
study area, 86 species (71.67%) were resident, 18 (15%) were summer visitors,
and 16 (13.34%) were winter visitors.
A total of 459 individuals of 81 species of seven
orders belonging to 27 families were recorded in the winter season and 577
individuals of 95 species of six orders belonging to 29 families were recorded
from the summer season. Fifty-six species of birds were found in both summer
and winter season (Table 1).
Shannon Wiener diversity index (H’) for the winter
season (January and February) was H’ = 3.93 whereas more diverse bird
assemblage was observed in the summer season (May and June) with the diversity
index of H’ = 4.006. The evenness index was found to be higher in winter (E =
0.6287) than in summer season (E = 0.5784) (Table 1).
Sorenson’s similarity index (SSI) of species
composition was observed to be 63.63% between summer and winter season. ANOVA revealed no significant variation in
species richness (F = 0.487; df = 1, 175; P =
0.486] and abundance (F = 2.903; df = 1, 175; P
= 0.090) of birds between two seasons among the point count locations.
The model selection results showed that elevation
consistently had a negative influence on species richness and diversity; as the
elevation increased the species richness decreased significantly (Estimate² =
-0.21, P < 0.001) (Fig. 3A & B).
Distance to the road as a predictor of human disturbance also had a
negative influence on species richness and diversity (Fig. 3C & D). Both
species richness and diversity were positively associated with the number of
fruiting trees as a proxy of resource availability, however, the results lacked
the statistical significance (Fig. 3E & F).
The beta-coefficient or slope of elevation (βelevation) was
-0.48 (SE = 0.05) and distance to road (βdistance to road) was -0.22
(SE = 0.05). The slope estimates of
number fruiting tree (βfruiting trees) for species richness analysis
was 0.14 (SE = 0.002). The positive beta
coefficient showed that for every one-unit increase in the predictor variable
(no. of fruiting trees), the response variable (species richness) increased by
the beta coefficient value. For negative
beta coefficient, species richness decreased by beta coefficient value for
every one-unit increase in elevation and distance to road. Since the 95%
confidence interval of the beta-coefficients did not overlap with zero, the
effects of these variables (species richness, elevation, no. of fruiting trees
and distance to road) are significant (P<0.05).
For both the species richness and diversity analysis, AICc based model selection predicted the elevation model
having the least AICc value as the most plausible
model in the candidate model set. The
model with only elevation as a regressor with smallest AICc
value (351.58) was the best fit as compared to other variable model sets (Table
2).
The habitat variables that were selected to find the
relationship between environmental variables and species were forest habitat,
riverbank, agricultural area, shrubland, grassland, scrubland, and barren
area. The Monte-Carlo permutation test
of significance of all canonical axes revealed no significant relationship
between the carnivorous species and habitat types (Trace=0.813, F-ratio=0.747, P=0.718)
(Fig. 4A). Insectivores showed strong
association (Trace= 0.843, F-ratio= 1.461, P=0.003) with shrubland and
scrubland habitats, whereas grassland habitat showed less impact in their
distribution. A large number of the
insectivore bird species including Black-throated Tit Aegithalos
concinnus, Greater Yellownape
Picus flavinucha,
Verditer Flycatcher Eumyias
thalassinus, Black-lored
Tit Parus xanthogenys,
Grey-headed Woodpecker Picus canus, and Streaked Laughingthrush Garrulax
lineatus were associated with forest habitat
(Fig. 4B).
For frugivore species, shrubland habitat followed by
the riverbank and grassland habitats had more significant impact on species
distribution (Trace=0.362, F-ratio=0.125, P=0.034). Red-billed Blue Magpie Urocissa
erythrorhyncha, Blue-throated Barbet Megalaima asiatica,
Grey Treepie Dendrocitta formosae, and Black-throated Sunbird Aethopyga saturata
showed strong association with shrubland habitat. Barbet species like Great Barbet Megalaima virens
and Golden-throated Barbet Megalaima franklinii were associated with agricultural areas.
Similarly, species like White-winged Grosbeak Mycerobas
carnipes and Crimson Sunbird Aethopyga
siparaja were associated with forest habitat
(Fig. 4C).
Granivore birds, represented by small number of species had no
significant association (Trace= 0.459, F-ratio= 0.744, P= 0.828) with
habitat types (Fig. 4D). Omnivore birds
depicted a significant relationship (Trace= 0.948, F-ratio= 1.351, P=
0.006) with habitat variables (Fig. 4E).
Bird species like Oriental White-eye Zosterops
palpebrosos, Black Bulbul Hypsipetes
leucocephalus, Asian Koel
Eudynamys scolopacea,
Scarlet Minivet Pericrocotus flammeus, Yellow-billed Blue Magpie Urocissa
flavirostris, and Green Shrike Babbler Pteruthius xanthochlorus
were associated with shrubland habitat.
Similarly, bird species such as Common Tailorbird Orthotomus
sutorius, Himalayan Bulbul Pycnonotus
leucogenys, Red-billed Leiothrix
Leothrix lutea, Beautiful Rosefinch Carpodacus pulcherrimus, and White-browed Fulvetta
Alcippe vinipectus
showed significant association with forest habitats. Very few species like Oriental Turtle Dove Streptopelia orientalis
and Common Pigeon Columba livia showed
association with other habitat variables such as scrubland, barren area and
grassland habitat rather than forest and shrubland habitats. These variables appeared to have a strong
impact on species distribution. Species
richness in response to agricultural land as a habitat variable revealed very
weak association.
This
study recorded a highly diverse avian fauna dominated by Passeriformes in the Kaligandaki River basin.
The high species richness might be attributed to habitat
complexity/heterogeneity (MacArthur 1964; Pan et al. 2016; Hu et al. 2018)
along an elevation gradient of the Kaligandaki River
basin, comprising riverine Alnus nepalensis forest, Schima
wallichi forest, mixed-forest with Tooni ciliata and Bombyx
ceiba, Pinus roxburghii forest, Pinus wallichiana forest, Betula utilis
forest including agricultural land, human settlement area, shrubberies,
grassland and scrublands. The study area covered an elevation range of
800–3,800 m from sub-tropical to sub-alpine habitats supporting diverse avian
fauna. At the lowest levels of the study
area there were subtropical forests of broadleaved Schima
wallichii, Castanopsis indica, and Pinus roxburghii
on dry slopes, as well as Alder Alnus nepalensis, which mainly occurred along rivers and
streams. Higher up were temperate
forests of mixed broadleaves, oaks (Quercus lamellosa,
Q. lanata, and Q. semecarpifolia)
and rhododendrons. In the wettest
places, bamboo jungles of Arundinaria species
were dominant. Coniferous forests,
mainly of Fir Abies spectabilis,
Blue Pine Pinus wallichiana, and Hemlock Tsuga
dumosa grow on the dry ridges and slopes. Above the temperate zone lie subalpine
forests of Birch Betula utilis, blue pine, and
junipers. Rhododendron and juniper scrub
grow in the alpine zone (Inskipp & Inskipp 2003).
Rivers and streams support a good variety of birds dependent on this
habitat, notably Crested Kingfisher Megaceryle
lugubris, four forktail
species, Brown Dipper Cinclus pallasii, White-capped Redstart Chaimarrornis
leucocephalus and Plumbeous
Water Redstart Rhyacornis fuliginosa. The
combination of highly varied topography, climate and wide altitude range has
resulted in many habitat types and associated rich bird species diversity
within the study area.
The
avian assemblage in any area or habitat type often changes seasonally (Avery
& Riper 1989; Moning & Müller 2008; Collins
& Edward 2014), under the influence of microclimatic and environmental
factors like temperature, humidity, rainfall, and food availability. Birds typically migrate from north to south
in the winter, and most arrive for breeding in Nepal in the summer. We observed no significant difference in
species richness between summer (95 species) and winter (81 species).
We observed a decline in species richness with
increasing elevation in the Kaligandaki River
basin. Similar observations have been
reported for other taxa and regions (Rahbek 1995,
2005; Basnet et al. 2016; Santillan et al. 2018), but the few studies in the
Himalaya have reported high species richness at middle elevations compared to
higher and lower elevations (Bhattarai & Vetaas
2006; Acharya et al. 2011; Joshi & Bhat 2015; Hu et al. 2018; Ding et al.
2019; Xingcheng et al. 2019; Pandey et al.
2020). Our result is in line with
previous studies showing a decline of species richness along elevational
gradients (McCain 2009; Santhakumar et al. 2018),
which has been attributed to limiting abiotic and biotic factors, such as harsh
climatic conditions or reduced resource availability at high elevations. As elevation increases, the vegetation types
and land topography gradually change from lower sub-tropical to sub-alpine,
with decreasing forest cover and increased low-productivity scrub and
meadows. Observed species richness was highest
at 850m and 2,000m within the study area.
At 850m the dense well-structured sub-tropical forest of Schima wallichii, Alnus nepalensis, Bombyx
ceiba, and Tooni ciliata
harbored a higher number of species. Additionally, the riverine area and
cultivated land with human settlement at this elevation supported more avian
fauna than in the higher altitudes. In
general, richness peaks at intermediate elevations appear to correspond closely
to transition zones between different vegetation types (Lomolino
2001). At 2,000m around the Ghasa forest, the transition zone between the two forest
types, the sub-tropical forest and temperate forest predominately with Pinus
wallichiana might have contributed to the
richness peak seen in this region. The
gradual decline of species richness above 2,000 m might suggest an abrupt
change in factors that limit avian richness, including poor vegetation and
harsh climatic conditions. At higher
elevations the stature of the forest decreased dramatically, and the climatic
conditions became increasingly severe with heavy winds during summer and
snowfall in winter. Such harsh and
unproductive environment at higher altitudes cause a decline in abundance and
distribution of invertebrate resources and scarcity of food items for birds,
and favors a very small number of species (Blake
& Loiselle 2000; Hu et al. 2018).
Besides this, trees were replaced by bushes, shrubs and rocky-mountains,
which negatively affected the avian fauna in this region.
Bird
species richness and diversity suggested a positive association with the number
of fruiting trees taken as proxy of resource availability within the study
area. Food availability is considered
one of the most important factors limiting bird richness and abundance (Strong
& Sherry 2000; Wu et al. 2013; Douglas et al. 2014; Pan et al. 2016). As the number of fruiting trees increased,
species richness was also higher, illustrating the positive impact of forest
resources on avian diversity. This might
be particularly a case for insectivorous species as the insectivore species constitute
substantial pool of overall species richness.
These results are consistent with previous studies which have supported
the energy (resource)-diversity hypothesis (Hurlbert
& Haskell 2003; Price et al. 2014; Pan et al. 2016), explaining that the sites
with greater available energy can support more individuals and, hence, more
species. Further, increase in number of
trees provides food resources, roosting and nesting sites to most of the forest
birds. Additionally, the fruiting trees
with flowers, fruits, and seeds attract a number of insects and hence support
the insectivores resulting in overall species richness increase. There was a significant relationship between
bird species assemblages and tree species assemblages in the eastern forests of
North America (Lee & Rotenberry 2005). This is consistent with the findings that the
species richness of insectivorous feeding guilds was associated to vegetation
structure and invertebrate biomass, while the richness of frugivores was linked
with fruit abundance, both supported by the forest stand and cover (Ferger 2014). The
distribution and abundance of many bird species are determined by the
configuration and composition of the vegetation (trees species and number) that
comprises a major element of their habitat (Morrison 1992; Block & Brennan
1993). As number of trees stands changes
along geographical and environmental gradients, any particular bird species may
appear, increase in abundance, decrease, and fade as habitat becomes more or
less suitable for its existence (Pidgeon et al. 2007).
The
impacts of roads on wildlife populations are extensive and well documented
around the globe (Fahrig & Rytwinski
2009). Distance to road as a
representation of disturbance variable with species richness and diversity was
tested and strong negative correlation was observed, revealing increase in
species richness near road and vice versa.
Many studies on birds have shown negative association to the roads such
that abundance, occurrence and species richness of birds are reduced near
roads, with larger reductions near high-traffic roads than near lower traffic
roads (Reijnen et al. 1995; Brotons
& Herrando 2001; Fuller et al. 2001; Burton et
al. 2002; Rheindt 2003; Peris & Pescador 2004; Pocock & Lawrence 2005; Palomino & Carrascal 2007; Griffith et al. 2010). Similar findings with road distance and
species richness was discussed where empirical findings showed that there was a
negative impact of roads and settlements on threatened birds of Chitwan
National Park, Nepal (Adhikari et al. 2019).
The main cause of the higher bird richness near roads in the Kaligandaki River basin may due to low traffic in newly
constructed roads and sparse human settlements and movements. High species richness near the road may be
due to higher detectability by the observers and possible preference of open
habitats by the birds.
Canonical
correspondence analysis showed that most of the feeding guilds including
insectivores, omnivores and frugivores were associated with forest, shrubland,
and agricultural area. The observed bird
species preferred forest habitat in comparison to other habitat types within
the study area. The main reason for such
preference could be available resources supplement by forest area in comparison
to other land use types. Forests provide
the indispensable resources required for the accomplishment of life cycles of
birds, including food for adults and nestlings and nesting sites. Avian fauna occurs on several trophic heights
in forests from primary consumers to vertebrate predators, as well as omnivores
and scavengers. Birds get nutrients from
nectar, fruits, seeds, and vegetative tissues including roots, shoots, and
leaves. Birds that consume the
vegetative parts of plants may also supplement their diet with other sources of
protein such as invertebrates found in different strata in forest habitat,
supporting insectivore species (Stratford & Sekercioglu
2015). These findings are supported by
many studies that explained increased structural complexity of vegetation is
associated with increased avian species richness (MacArthur & MacArthur
1961; MacArthur et al. 1962; MacArthur et al. 1966; Orians
& Wittenberger 1991).
One
characteristic of forest structure is foliage height diversity and is defined
by the variation in the layers of a forest which positively supports species
richness. Increasing foliage height
diversity is associated with increasing avian diversity, particularly insectivores
(MacArthur & MacArthur 1961; MacArthur et al. 1962), with increasing
foraging sites and increased niches available to exploit (MacArthur et al.
1966). Another study of avian
communities in urban parks across Beijing showed that the vegetation structure
and foliage height diversity was the most important factor influencing avian
species diversity than park area (Xie et al.
2016). Rompre
et al. (2007) found that plant species richness, precipitation, forest age, and
topography strongly affected avian diversity in lowland, Panama rain forests. In the present study, lower number of species
in scrubland and barren area in higher altitudes (above 2,600m) could be
attributed to scarce vegetation and low productivity due to climatic
constraints. The presence of forest
stands, forest edges and shrubs, therefore, supports more bird species are
important factors in driving species composition (Basnet et al. 2016). Similar results were described in farmland in
central Uganda, where richness of forest-dependent bird species showed a
positive relationship with the number of native tree species (Douglas et al.
2014). Significant association of
species with river bank area can be explained by the presence of aquatic avian
fauna such as Brown Dipper Cinclus pallasii, Blue Whistling Thrush Myophonus
caeruleus, Plumbeous
Water Redstart Rhyacornis fuliginosa, White-capped Redstart Chaimarrornis
leucocephalus, forktails,
and wagtails dwelling near and around streams and rivers depending mostly on
aquatic invertebrates in or under the water, river banks, and riverine
vegetation. Study on Tibetan region of
the Himalaya indicated that the species richness of overall birds is positively
correlated with forest habitat, productivity, and habitat heterogeneity (Pan et
al. 2016). Higher species richness in
forest habitats especially in lower elevations and strong association of birds
with fruiting trees for resource utilization along the Kaligandaki
River basin indicate that the existing primary forest in the basin is important
for avian conservation.
Our survey of birds during summer and winter showed
highly diverse avian fauna, but it did not cover all seasons, nor all of the
Annapurna Conservation Area. A more
extensive study is recommended to more comprehensively explore avian species
within this area. Apart from developing
checklists of birds, studies of patterns and processes affecting species, and
diversity of avian fauna in other parts of the conservation area are
recommended to assist conservation efforts.
The
Kaligandaki Valley river basin, an important part of
the Annapurna Conservation Area, one of the IBAs in central Himalaya has highly
diverse avian fauna dominated by Passeriformes.
High abundance of resident insectivores does not bring much variation in
species richness between summer and winter.
Restrictive abiotic and biotic factors, such as harsh climatic
conditions or reduced resource availability at high elevations, cause a decline
in bird species richness with elevation.
The number of fruiting trees has a positive influence on avian species
richness and diversity.
Annex I. Checklist of bird species from Kaligandaki River basin, Annapurna Conservation Area, Nepal
|
Order, Family, Common name |
Scientific name |
Feeding guild |
Migratory status |
Species
code used in ordination |
|
GALLIFORMES |
|
|||
|
Phasianidae |
||||
|
Black Francolin |
Francolinus francolinus |
Omnivore |
Resident |
Fra fra |
|
Kalij Pheasant |
Lophura leucomelanos |
Insectivore |
Resident |
Lop leu |
|
PICIFORMES |
|
|||
|
Megalaimidae |
||||
|
Blue-throated Barbet |
Megalaima asiatica |
Frugivore |
Resident |
Meg asi |
|
Golden-throated Barbet |
Megalaima franklinii |
Frugivore |
Resident |
Meg fra |
|
Great Barbet |
Megalaima virens |
Frugivore |
Resident |
Meg vir |
|
Picidae |
|
|||
|
Greater Yellownape |
Picus flavinucha |
Insectivore |
Resident |
Pic fla |
|
Grey-headed Woodpecker |
Picus canus |
Insectivore |
Resident |
Pic can |
|
Fulvous-breasted Woodpecker |
Dendrocopos macei |
Insectivore |
Resident |
Den mac |
|
Speckled Piculet |
Picumnus innominatus |
Insectivore |
Resident |
Pic inn |
|
CUCULIFORMES |
|
|||
|
Cuculidae |
||||
|
Eurasian Cuckoo |
Cuculus canorus |
Insectivore |
Summer visitor |
Cuc can |
|
Lesser Cuckoo |
Cuculus poliocephalus |
Insectivore |
Summer visitor |
Cuc pol |
|
Asian Koel |
Eudynamys scolopaceus |
Omnivore |
Resident |
Eud sco |
|
COLUMBIFORMES |
|
|||
|
Columbidae |
||||
|
Common Pigeon |
Columba livia |
Granivore |
Resident |
Col liv |
|
Hill Pigeon |
Columba rupestris |
Granivore |
Resident |
Col rup |
|
Oriental Turtle Dove |
Streptopelia orientalis |
Granivore |
Summer visitor |
Str ori |
|
Spotted Dove |
Stigmatopelia chinensis |
Granivore |
Resident |
Sti chi |
|
Wedge-tailed green Pigeon |
Treron sphenurus |
Granivore |
Resident |
Tre sph |
|
CICONIFORMES |
|
|||
|
Scolopacidae |
||||
|
Green Sandpiper |
Tringa ochropus |
Insectivore |
Winter visitor |
Tri och |
|
ACCIPITRIFORMES |
|
|||
|
Accipitridae |
||||
|
Black Kite |
Milvus migrans |
Carnivore |
Winter visitor |
Mil mig |
|
Steppe Eagle |
Aquila nipalensis |
Carnivore |
Winter visitor |
Aqu nip |
|
Egyptian Vulture |
Neophron percnopterus |
Carnivore |
Resident |
Neo per |
|
FALCONIFORMES |
|
|||
|
Falconidae |
||||
|
Common Kestrel |
Falco tinnunculus |
Carnivore |
Winter visitor |
Fal tin |
|
PASSERIFORMES |
|
|
|
|
|
Prunellidae |
||||
|
Alpine Accentor |
Prunella collaris |
Omnivore |
Resident |
Pru col |
|
Altai Accentor |
Prunella himalayana |
Omnivore |
Winter visitor |
Pru him |
|
Brown Accentor |
Prunella fulvescens |
Omnivore |
Winter visitor |
Pru ful |
|
Corvidae |
|
|||
|
Alpine Chough |
Pyrrhocorax graculus |
Omnivore |
Resident |
Pyr gra |
|
House Crow |
Corvus splendens |
Omnivore |
Resident |
Cor spl |
|
Large-billed Crow |
Corvus macrorhynchos |
Omnivore |
Resident |
Cor mac |
|
Northern Raven |
Corvus corax |
Omnivore |
Resident |
Cor cor |
|
Red-billed Blue Magpie |
Urocissa erythrorhyncha |
Frugivore |
Resident |
Uro ery |
|
Red-billed Chough |
Pyrrhocorax pyrrhocorax |
Omnivores |
Resident |
Pyr pyr |
|
Rufous Treepie |
Dendrocitta vagabunda |
Frugivore |
Resident |
Den vag |
|
Grey Treepie |
Dendrocitta formosae |
Frugivore |
Resident |
Den for |
|
Yellow-billed Blue Magpie |
Urocissa flavirostris |
Frugivore |
Resident |
Uro fla |
|
Dicruridae |
|
|||
|
Ashy Drongo |
Dicrurus leucophaeus |
Insectivore |
Summer visitor |
Dic leu |
|
Black Drongo |
Dicrurus macrocercus |
Insectivore |
Resident |
Dic mac |
|
Spangled Drongo |
Dicrurus hottentottus |
Insectivore |
Resident |
Dic hot |
|
Muscicapidae |
|
|||
|
Asian Paradise-flycatcher |
Terpsiphone paradisi |
Insectivore |
Summer visitor |
Ter par |
|
Blue-capped Redstart |
Phoenicurus coeruleocephala |
Insectivore |
Winter visitor |
Pho coe |
|
Blue-fronted Redstart |
Phoenicurus frontalis |
Omnivore |
Summer visitor |
Pho fro |
|
Common Stonechat |
Saxicola torquatus |
Insectivore |
Resident |
Sax tor |
|
Himalayan Bluetail |
Tarsiger rufilatus |
Insectivore |
Resident |
Tar ruf |
|
Hogdson's Redstart |
Phoenicurus hodgsoni |
Insectivore |
Winter visitor |
Pho hod |
|
Little Forktail |
Enicurus scouleri |
Insectivore |
Resident |
Eni sco |
|
Pied Bushchat |
Saxicola caprata |
Insectivore |
Resident |
Sax cap |
|
Grey Bushchat |
Saxicola ferreus |
Insectivore |
Resident |
Sax fer |
|
Plumbous Water Redstart |
Rhyacornis fuliginosa |
Insectivore |
Resident |
Rhy ful |
|
Spotted Forktail |
Enicurus maculatus |
Insectivore |
Resident |
Eni mac |
|
Verditer Flycatcher |
Eumyias thalassinus |
Insectivore |
Summer visitor |
Eum tha |
|
White-capped Redstart |
Chaimarrornis leucocephalus |
Insectivore |
Resident |
Cha leu |
|
White-browed Bush Robin |
Tarsiger indicus |
Insectivore |
Resident |
Tar ind |
|
Oriental Magpie Robin |
Copsychus saularis |
Insectivore |
Resident |
Cop sau |
|
White-tailed Rubythroat |
Luscinia pectoralis |
Insectivore |
Resident |
Lus pec |
|
White-throated Redstart |
Phoenicurus schisticeps |
Insectivore |
Winter visitor |
Pho sch |
|
Hirundinidae |
|
|||
|
Barn Swallow |
Hirundo rustica |
Insectivore |
Resident |
Hir rus |
|
Fringillidae |
|
|||
|
Beautiful Rosefinch |
Carpodacus pulcherrimus |
Omnivore |
Summer visitor |
Car pul |
|
Collared Grosbeak |
Mycerobas affinis |
Omnivore |
Resident |
Myc aff |
|
Common Rosefinch |
Carpodacus erythrinus |
Omnivore |
Summer visitor |
Car ery |
|
Spot-winged Grosbeak |
Mycerobas melanozanthos |
Frugivore |
Resident |
Myc mel |
|
White-browed Rosefinch |
Carpodacus thura |
Omnivore |
Summer visitor |
Car thu |
|
White-winged Grosbeak |
Mycerobas carnipes |
Frugivore |
Resident |
Myc car |
|
Pycnonotidae |
||||
|
Black Bulbul |
Hypsipetes leucocephalus |
Omnivore |
Resident |
Hyp leu |
|
Himalayan Bulbul |
Pycnonotus leucogenys |
Omnivore |
Resident |
Pyc leu |
|
Red-vented Bulbul |
Pycnonotus cafer |
Omnivore |
Resident |
Pyc caf |
|
Timallidae |
|
|||
|
Black-chinned Babbler |
Stachyridopsis pyrrhops |
Insectivore |
Resident |
Sta pyr |
|
Green Shrike Babbler |
Pteruthius xanthochlorus |
Omnivore |
Resident |
Pte xan |
|
Paridae |
|
|||
|
Black-lored Tit |
Parus xanthogenys |
Insectivore |
Resident |
Par xan |
|
Black-throated Tit |
Aegithalos concinnus |
Insectivore |
Resident |
Aeg con |
|
Coal Tit |
Periparus ater |
Insectivore |
Resident |
Per ate |
|
Great Tit |
Parus major |
Insectivore |
Resident |
Par maj |
|
White-throated Tit |
Aegithalos niveogularis |
Insectivore |
Resident |
Aeg niv |
|
Green-backed Tit |
Parus monticolus |
Insectivore |
Resident |
Par mon |
|
Nectarinidae |
|
|||
|
Black-throated Sunbird |
Aethopyga saturata |
Frugivore |
Resident |
Aet sat |
|
Crimson Sunbird |
Aethopyga siparaja |
Frugivore |
Resident |
Aet sip |
|
Fire-breasted Flowerpecker |
Dicaeum ignipectus |
Frugivore |
Resident |
Dic ign |
|
Green-tailed Sunbird |
Aethopyga nipalensis |
Frugivore |
Resident |
Aet nip |
|
Purple Sunbird |
Nectarinia asiatica |
Frugivore |
Resident |
Nec asi |
|
Turdidae |
|
|||
|
White-throated Laughingthrush |
Garrulax albogularis |
Insectivore |
Resident |
Gar alb |
|
Blue-capped Rock Thrush |
Monticola cinclorhynchus |
Insectivore |
Summer visitor |
Mon cin |
|
Blue Rock Thrush |
Monticola solitarius |
Insectivore |
Summer visitor |
Mon sol |
|
Blue Whistling Thrush |
Myophonus caeruleus |
Omnivore |
Resident |
Myo cae |
|
Streaked Laughing Thrush |
Garrulax lineatus |
Insectivore |
Resident |
Gar lin |
|
Variegated Laughing Thrush |
Garrulax variegatus |
Insectivore |
Resident |
Gar var |
|
Sylviidae |
|
|||
|
Blyth's Leaf Warbler |
Phylloscopus reguloides |
Insectivore |
Resident |
Phy reg |
|
Grey-hooded Warbler |
Phylloscopus xanthoschistos |
Insectivore |
Resident |
Phy xan |
|
Greenish Warbler |
Phylloscopus trochiloides |
Insectivore |
Resident |
Phy tro |
|
Hume's Leaf Warbler |
Phylloscopus humei |
Insectivore |
Summer visitor |
Phy hum |
|
Lemon-rumped Warbler |
Phylloscopus chloronotus |
Insectivore |
Winter visitor |
Phy chl |
|
Red-billed Leiothrix |
Leiothrix lutea |
Omnivore |
Resident |
Leo lut |
|
Rufous Sibia |
Malacias capistratus |
Omnivore |
Resident |
Mal cap |
|
Stripe-throated Yuhina |
Yuhina gularis |
Omnivore |
Resident |
Yuh gul |
|
White-browed Fulvetta |
Alcippe vinipectus |
Omnivore |
Resident |
Alc vin |
|
Yellow-browed Warbler |
Phylloscoppus inornatus |
Insectivore |
Winter visitor |
Phy ino |
|
Cinclidae |
|
|||
|
Brown Dipper |
Cinclus pallasii |
Insectivore |
Resident |
Cin pal |
|
Laniidae |
|
|||
|
Brown Shrike |
Lanius cristatus |
Carnivore |
Winter visitor |
Lan cri |
|
Grey-backed Shrike |
Lanius tephronotus |
Carnivore |
Summer visitor |
Lan tep |
|
Long-tailed Shrike |
Lanius schach |
Carnivore |
Resident |
Lan sch |
|
Certhiidae |
|
|||
|
Brown-throated Treecreeper |
Certhia discolor |
Insectivore |
Resident |
Cer dis |
|
Sittidae |
|
|||
|
Chestnut-bellied Nuthatch |
Sitta cinnamoventris |
Omnivore |
Resident |
Sit cin |
|
Velvet-fronted Nuthatch |
Sitta frontalis |
Omnivore |
Resident |
Sit fro |
|
Wall creeper |
Tichodroma muraria |
Omnivore |
Winter visitor |
Tic mur |
|
Sturnidae |
|
|||
|
Common Myna |
Acridotheres tristis |
Cmnivore |
Resident |
Acr tri |
|
Cisticilidae |
|
|||
|
Common Tailorbird |
Orthotomus sutorius |
Insectivore |
Resident |
Ort sut |
|
Passeridae |
|
|||
|
Eurasian Tree Sparrow |
Passer montanus |
Granivore |
Resident |
Pas mon |
|
House Sparrow |
Passer domesticus |
Granivore |
Resident |
Pas dom |
|
Russet Sparrow |
Passer rutilans |
Omnivore |
Resident |
Pas rut |
|
Motacillidae |
|
|||
|
Grey Wagtail |
Motacilla cinerea |
Insectivore |
Summer visitor |
Mot cin |
|
Rosy Pipit |
Anthus roseatus |
Omnivore |
Summer Visitor |
Ant ros |
|
Olive-backed Pipit |
Anthus hodgsoni |
Insectivore |
Winter visitor |
Ant hod |
|
White Wagtail |
Motacilla alba |
Insectivore |
Summer visitor |
Mot alb |
|
White-browed Wagtail |
Motacilla maderaspatensis |
Insectivore |
Resident |
Mot mad |
|
Yellow Wagtail |
Motacilla flava |
Insectivore |
Winter visitor |
Mot fla |
|
Campephagidae |
|
|||
|
Long-tailed Minivet |
Pericrocotus ethologus |
Insectivore |
Resident |
Per eth |
|
Scarlet Minivet |
Pericrocotus flammeus |
Insectivore |
Resident |
Per fla |
|
Zosteropidae |
|
|||
|
Oriental White-eye |
Zosterops palpebrosus |
Omnivore |
Resident |
Zor pal |
|
Emberizidae |
|
|||
|
Rock Bunting |
Emberiza cia |
Granivore |
Resident |
Emb cia |
|
Little Bunting |
Emberiza pussila |
Omnivore |
Winter visitor |
Emb pus |
|
Cisticolidae |
|
|||
|
Striated Prinia |
Prinia crinigera |
Insectivore |
Resident |
Pri cri |
|
Rhipiduridae |
|
|||
|
White-throated Fantail |
Rhipidura albicollis |
Insectivore |
Resident |
Rhi alb |
|
Yellow-bellied Fantail |
Chelidorhynx hypoxantha |
Insectivore |
Summer visitor |
Che hyp |
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