Bird diversity and distribution along the Sunkosh River, Tsirang and Dagana District in southern Bhutan


Bachelor Thesis, 2016

47 Pages, Grade: 83


Excerpt

Table of Contents

ACKNOWLEDGEMENTS

LIST OF ACRONYMS

ABSTRACT

List of Figures

List of Tables

CHAPTER ONE
Introduction
1.1 Background
1.2 Problem Statement
1.3 Research Question
1.4 Objectives
1.5 Scope and Limitation

CHAPTER TWO
Literature Review
2.1 Evolutionary History
2.2 Ecological Importance of Birds
2.3 Diversity
2.4 Distribution
2.5 Conservation Threat

CHAPTER THREE
Materials and Methods
3.1 Study Area
3.2 Materials
3.3 Methods
3.4 Data analysis

CHAPTER FOUR
Results and Discussion
4.1 Bird Species Composition
4.2 Bird Species Diversity
4.3 Relationship between altitude and BSC, BSD, SE
4.4 Relationship between Species composition, species diversity and species evenness
4.5 Species Distribution
4.6 Bird abundance in the entire study area

CHAPTER FIVE

Conclusion and Recommendation

References

Annexures

List of Figures

Figure 3.1. Map of the study area

Figure 4.1. Bird species composition in three study sites

Figure 4.2. Representing IUCN status of the bird species

Figure 4.3. Number of bird species against each family in the entire study areas

Figure 4.4. Bird species diversity index (H') in the three study sites

Figure 4.5. Relationship between different diversity indices and habitat types

Figure 4.6. Species evenness index in three study sites

Figure 4.7. Bird abundance and richness in the entire study areas

List of Tables

Table 4.1. Total bird species recorded in the entire study area

Table 4.2. Correlation between Altitude, BSC, BSD and SE

Table 4.3. Abundance of bird families in the river confluence area

Table 4.4. Abundance of bird families in the settlement area

Table 4.5. Birds recorded with their families with abundance in the undisturbed forest area

ACKNOWLEDGEMENTS

I am very much grateful to my supervisor Mrs. Sushila Rai, Lecturer, Department of Forests, College of Natural Resources for her valuable advices, continuous support and guidance from the commencement of my field work till date for writing this thesis. I also owe my gratitude to the College of Natural Resources for offering such Bachelor of Science in Forestry course with the inclusion of dissertation program. I would also like to dedicate my gratitude to the Ministry of Agriculture and Forests for initiating the long term studies opportunity for the in-service people like me.

I am extremely grateful to Mr. Sonam Dendup (My colleague), Mr. Dawa Tshering (My colleague) and Mr. Rinchen Choeda (Son of Tshedup Drukpa) for their equal involvement in the field during the bird survey. I am also grateful to Mr. Tshedup Drukpa, Sr. Forester, Dzongkhag Forestry sector, Sunkosh, Tsirang Division, for being with me in the field during my first and second round of bird survey.

My heartfelt gratitude also lies to Mr. Norbu Gyalpo, District Education Officer, Dagana for lending me his professional camera and Mr. Pema Norbu (Eldest Nephew), Sr. Forest Ranger III, Thimphu Forest Division for providing his binoculars without which this research would not have been possible. An extreme gratitude also owe to Mr. Gyem Tshewang (my colleague) and Mr. Phuntsho (my colleague) for assisting me in data analysis, production of simple study area map and providing necessary procedures in writing this thesis.

Lastly, I would like to thank my loving wife Bishnu Kumari, My son Sonam Wangden Tobgay, Dhoje Rigdriel Tobgay and my daughter Namsye Tsoimeto Tobgay, for their care and support throughout my academic life in the College of Natural Resources with great deal of patience and understanding.

LIST OF ACRONYMS

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ABSTRACT

The study of bird diversity and distribution along the Sunkosh River, Tsirang and Dagana District, Bhutan was carried out in the winter months to provide comprehensive data on both aquatic and terrestrial birds. This paper focuses on providing some information on the composition, diversity and abundance of various bird species recorded along the Sunkosh River. In order to accomplish this aim, point count survey method was used to generate data for ecological analysis. A total of 59 bird species belonging to 30 families were recorded during the study. The study was divided into three major habitats: River confluence (Site 1), settlement (Site 2) and undisturbed forest (Site 3). The instruments used were Garmin etrek Global Positioning System (GPS), a pair of binoculars for bird’s identification, a field guide (Birds of Bhutan), survey data sheet and a 300 meters measuring tape. The data were tested with the Kolmogorov-Smirnov method to determine distribution level and bird diversity was assessed using Shannon-Weiner Diversity Index, while parametric tests were applied for all data. The results showed that bird species diversity was normally distributed in all the sites, site 3 ensured the highest diversity (3.16) compared to site 1: (2.53) and site 2: (3.05). Bird species composition in three habitat types was found statistically significant; correlation result revealed that bird species composition and bird species diversity were negatively correlated with altitude.The most abundant bird species along the River confluence and Settlement area was Red-vented Bulbul, but it was White-crested Laughingthrush in the undisturbed forest.

Keywords: Birds, Distribution, Diversity, Habitat, Species Richness,

CHAPTER ONE Introduction

1.1 Background

Bhutan has been fairly well shielded by ornithological surveys (Choudhury, 2007) and the intact country forms a part of Eastern Himalaya Endemic Bird area (Stattersfield et al., 1998). Dagana District is positioned in the southern part of Bhutan with an imprecise area of 1389 kilometers. The elevation ranges from 600 meters to 3800 meters above the sea level with a total population estimate about 25,070. The District falls within the temperate zone in the north and sub-tropical zone in the south (Dagana Dzongkhag Administration, 2015).

As per United Nations Environment Program [UNEP] and Convention on Conservation of Migratory Species(UNEP, 2009), 9856 bird species are documented worldwide. Over 800 species of birds are estimated to be found in Bhutan of which frequent numbers of winter visitors, such as migrant thrushes are found in addition to 450 species of resident birds(Sherpa, 2000). Forest is the most significant habitat for birds by supporting around 75% of all bird species while only 45% of all bird species have adapted to humans modified habitats (Birdlife International, 2008). Human activities such as farming, settlement, charcoal making, pole cutting and firewood collection have contributed in removal of forests (degradation) which has extensively damaged the natural habitat of birds, affecting their variety and variability (Storch et al., 2003).

Human beings have used birds in different ways such as feeding purposes, communication in ancient eras, as an agent of dispersal or pollination and biological control like Rodentia (Tabur and Ayvaz, 2005). According to Sekercioglu et al. (2004), the major ecosystem processes like pollination, seed dispersal and decomposition will decrease as the result of extinction of 6-14% of all bird species by 2100. For the reason thatmany threats to bird populations including habitat loss, fragmentation and severe anthropogenic pressures, there is a need to study the current composition and status of bird species diversity as a basis for future monitoring and implementation of appropriate conservation measures (Choudhury, 1991;Chandra and Singh, 2004). Birds constitute one of the common fauna of all habitat types, and because they are reactive to change, their diversity and abundance can reflect ecological trends in other biodiversity (Furness and Greenwood, 1993). Because of their highly-specific habitat requirements, birds become increasingly intolerant of even slight ecosystem disturbance (Schwartz and Schwartz, 1951).

1.2 Problem Statement

Since the conservation based actions are focused only on critically endangered species of birds, even the baseline data for other bird species are lacking in Bhutan (Inskipp, 1993). The planning of the construction of reservoir with a production capacity of 2560 MW of electricity(Dorji, 2009)in the proposed study site is questionable for the conservation of terrestrial and aquatic avian community with the risks and threats associated in line to the anthropogenic activities. Land development and urbanization present particular challenges to conservation biologists. Although settlement expansion has resulted in the conversion of crop-land, pastures, and forests into built environments on a massive scale (Alig and Healy (1987), little is known about the effects of these expansion on ecosystems, communities, species, and populations because ecologists have traditionally worked in pristine, or relatively pristine, environments(Cairns, 1988).

Existences of trees, bushes, creepers are very important to them (Lim et al., 2003; Hargrove and Rotenberry, 2011). Climate change is a subject of concern now a days. Hence there is a need to monitor common birds of a locality to assess the degree of such change of environment for sustainable development (Furness and Greenwood, 1993). Change in the population of these local birds has stimulated various speculations to link with the possible environmental causes (Balmori and Hallberg, 2007). It is a very difficult task to separate the biotic and abiotic factors due to their mutual interactions either directly or indirectly (Preston et al., 2008). In this present era, conservation plans and activities are focused primarily on critically endangered species of birds and lack of baseline data for other bird species may lead habitat degradation, depletion and local extinction. The lack of baseline data in the proposed study area is the main rational behind this research study. The construction of reservoir in the proposed study area may invite stress and threat to the habitats of terrestrial and aquatic avian community. This study will serve as a baseline data for the bird diversity and its distribution. Future scientific studies like comparative study on diversity, richness and distribution ecology can be based on the data obtained from this study.

1.3 Research Question

1. What are the species diversity, species richness and evenness of birds in three different habitats (River habitats, settlement and Undisturbed forests) along the Sunkosh River, Tsirang and Dagana?

1.4 Objectives

1.4.1 To assess the bird species diversity and distribution along the Sunkosh River, Tsirang and Dagana District.

1.4.2 To compare bird species diversity between river confluence, settlement area and undisturbed natural forest.

1.5 Scope and Limitation

The primary objective of this research is to produce a reliable baseline data on bird diversity, species richness and species evenness as it is done for the first time which would serve very important source of information. Therefore it is being under taken to assess the richness, diversity and species evenness. The information supports to understand which species are most important, which might require special management because of their poor status and which might be so rare, so as to be in need of further protection elsewhere within their ranges.

However this is a onetime short study only in winter, therefore outcome of this paper cannot be considered ultimate result since all environmental factors that influences richness, diversity and evenness could not be considered for study in detail. To make the best decisions, it is most important that the information on which such decisions are made is as accurate, systematic and representative as possible. Baseline counts will come to be greatly valued when repeated in the future.

CHAPTER TWO Literature Review

2.1 Evolutionary History

According to the proposal made by (Feduccia, 1995), due to the mass extinction, avian ancestries disappeared during the Cretaceous period and the “explosive adaptive radiation” succeeded the surviving ancestries in the Cenozoic era (Feduccia, 2003). The dinosaurian origin of birds, the arboreal origin of avian flight and the origin of feathers prior to flapping are provided extraordinarily by the new fossils of birds and dinosaurs. Modern bird resembles the Mesozoic assemblages of Enantiornithes group and the Ornithurae(Zhou, 2004).

Clarke et al. (2005) provided apparent evidence that cousins of living birds coexisted with dinosaurs more than 65 million years ago. Evidence from a new species called Vegavisiaai indicates that these birds lived in the Cretaceous and must have survived the Cretaceous mass extinction event that included the disappearance of all other dinosaurs. Analysis of the fossil, discovered in Antarctica in 1992, revealed a new species in the group Anseriformes, which includes ducks and geese. Slack et al., (2006) described the earliest penguin fossils and analyzed complete mitochondrial genomes from an albatross, a petrel, and a loon. The penguin fossils were from a Paleocene (early tertiary) formation just above a well-known Cretaceous/Tertiary boundary site.

2.2 Ecological Importance of Birds

Birds are good environmental indicators revealing the state of the ecosystems such as forest edges, wetlands and major river basins. They also act as dispersal agents in transferring nutrients and spores from one place to another during their migration and local movements(Niemi, 1985). The avian habitat is roughly divided into forest, scrub and wetlands, although many species require a mixed type of habitat. It also act as an agent of biological control and bio-indicators according to Iowa Nature Mapping. From the perspective of ecosystem functions, birds are crucial for maintaining ecosystem and the resilience. The genetic linking characteristics of seed dispersing frugivores and pollinating nectarivores helps in carrying genetic materials for regeneration from one individual of plants to another (Sekercioglu, 2006).

Diversification of birds plays a very important role in the health of an ecosystem. Birds play an important role in ecosystem by being as a part of the food web. They are potential pollinators and bio-indicators. They occupy various types of habitats, from open field to forest, desert to High Mountain and even in ice zone where it is quite tough for a human or other animals to live. However, birds can influence various mode of life in the wetland ecosystem. In a wetland ecosystem biotic factors are mostly dependent on the seasons and hydrology(Hussain, 1995).

2.3 Diversity

Diversity is one of the most important community attributes which can determine stability, productivity and migration (Stirling and Wisley, 2001). An estimate of 1855 out of 9856 bird species in the world are migratory, out of which, 262 are seabirds, 343 are altitudinal migrants, 181 are nomadic, 1593 are migratory land and waterbirds. There are about 10,000 bird species in the world widespread from the poles to the equator, deserts to the middle of the oceans, on the highest mountains to the center of the cities and everywhere as an eye-catching form of animal life (Tabur and Ayvaz, 2005).

Since the diversity and distribution of birds along the landscape are not uniform (Bibby et al., 1992), their patterns are intensely associated to environmental factors like climate, topography and habitats. Tropical mountains are considered for sheltering high diversity of avifauna with many other flora and fauna (Jankowski et al., 2009) and the case study conducted by Bideberi in 2013, stated that the highest diversity of bird was found in forest area and the lowest in the settlement area. Habitat diversity or spatial heterogeneity influences the diversity of birds positively (Mac Arthur, 1965; Rafe et al., 1985; Pyrovetsi and Givelli, 1988). Larger area of the habitat tends to increase the bird diversity (Terborgh, 1973; Galli et al., 1976).

In Bhutan, with an additional discovery of four new birds’ species to the discovery of two birds in August, 2015, the record of bird species reached to 699 species in total. The newly discovered birds are Jacobin Cuckoo (Clamator jacobinus), Stork-billed kingfisher (Pelargopsis capensis), Greater Sand Plover (Charadrius leschenaultii) and the little owl (Athene noctua) which are discovered in October, 2015(Wangdi, 2015). In the Neotropics, birds have been cited as good indicators of forest health because both abundance and diversity of bird species is effected by habitat disturbance (Mas and Dietsch, 2004; Harvey et al., 2006).

2.4 Distribution

According to Geer (2010), the wetland characteristics such as water level, quality of water, availability and distribution of food resources and suitable roosting site describes the species richness and relative abundance of waterbirds species. As per the study result of Thinh (2006), the structure of vegetation enlightens the diversity of bird species but the floristic composition of tree layer is poor in expressing the species diversity. According to the study done by Mahr and Jones, (2005), the diversity and abundance of birds are strongly associated with habitats that are productive and lush in nature comprising of different canopy levels and various ages and species of trees and shrubs and rivers, with their associated vegetation, are crucial sources of food, refuge, and other resources for animals (Carothers et al., 1974).

Birds occur on land, sea, freshwater and in every habitat from deserts to the highest mountains(Bishop, 1999)and in a biodiversity conservation networks, riverside habitats are a significant place with high variety of abiotic parameters which creates a precondition for high species richness in flora and fauna(Kambourova, 2000). Birds are habitat specific and some can occupy more than one habitat type, however because of land uses changes, most of the birds have been displaced from their original habitats (Burgess et al., 2002). Forests have been converted to settlement, agricultural field and pasture land, sometimes to open land. Agriculture and other human activities have fragmented many plant and animal habitats into small scattered patches. These human activities have an impact on bird species abundance, distribution and diversity due to isolation and fragmentation (Westphal et al., 2006).

2.5 Conservation Threat

According to United States Fish and Wildlife Services (2014), the modification of stream flow due to the construction of hydropower project has both short and long term impacts on aquatic life and water quality. The habitats for migratory birds are fragmented and creates flight hazard by transmission line corridors. Changes in land use pattern results in the degradation of habitat and these habitat degradation is regarded as the most known causes of decline in waterfowl populations(Arzel, 2015)and the planned reservoir construction in the proposed study area may cause decline in both terrestrial and aquatic bird populations(Dorji, 2009).

Due to anthropogenic activities, Himalayan region have lost its biodiversity to a large extent. Increasing demand of natural resources attracted people towards this region and this leads to huge colonization from the outside. Rapid population growth and economic development is also responsible for overexploitation of natural resources in this hotspot. Other threats to forests include logging, mining for ore, firewood collection, and charcoal production. With this scenario, challenge before the ecologist or conservationists is to identify the areas that need immediate conservation actions (Karmakar and Bhattacharya, 2010). As per the study on using birds as indicators of biodiversity by Gregory et al. (2003) on UK farmland, the decline in the populations of birds have been directly proportional to the decline in the populations of invertebrates and plants due to changes in land use.

According to the report of Birdlife International (2010), the world’s biodiversity is being lost faster than ever. It loses its capacity to deliver the ecosystem services due to the human disturbances. The world’s governments have made commitments through the Convention on Biological Diversity (CBD) to tackle this issue to safeguard ecosystem, species and genes where extinction and decline of threatened species is prevented and their status improved. Rapid population growth and economic development is also responsible for overexploitation of natural resources in this hotspot. With this scenario, the challenges for the ecologist or conservationists are to identify the areas that need immediate conservation action. Processes associated with urbanization are one of the major causes of landscape change and represent an important threat to biodiversity (Wilcox and Murphy, 1985).

Urban planners need better information about the factors affecting the distribution of species and structure of communities in order to create or maintain biodiversity in urban areas. Conservation or restoration efforts related to urban wildlife focus on limiting artificial habitat, developing citizen participation in wildlife conservation, improving the quality of life of urban dwellers, and educating them about ecological concepts (Niemela, 1999). Birds are facing several threats such as deforestation, hunting, habitat loss and climatic changes(Parsons, 1935). Birds are ideal bio-indicators and useful models for studying a variety of environmental problems, and the importance of local landscapes for avian conservation can only be understood by knowing the structure of the bird community in the region concerned (Kattan and Franco, 2004).

CHAPTER THREE Materials and Methods

3.1 Study Area

The Punatshangchhu (referred to as Sunkosh River in this paper) has a total length of about 320 kilometers from its source in Bhutan to its confluence point with Brahmaputra in India(Choden, 2009). Therefore its river basin is one of the major river basins in Bhutan which cover six administrative Districts with human population of more than 162071 living in the basin of this river(Choden, 2009). The human Population density in this basin is only 8 persons per km² (Population and Housing Census of Bhutan, 2005). The research site falls under two Districts namely Tsirang and Dagana represented in Figure 1. Changchey Khola and Dagachu are two rivers that meets at Sunkosh. Sunkosh (Figure 3.1) is a junction area of two Districts (Tsirang and Dagana).

The focus is centered at Dagana District since the Study area falls under Dagana District which is located in the southern part of Bhutan with an approximate area of 1389 square kilometers which lies between 26.580 – 27.590 north and 90.040 east. The elevation ranges from 265 meters to 3800 meters above the sea level with a total population estimate about 25,070. The District falls within the temperate zone in the north and sub-tropical zone in the south (DDA, 2015). Sunkosh River flowing in between Tsirang and Dagana District passes through Sunkosh satellite town where Royal Government of Bhutan has planned to build huge reservoir in the area(Dorji, 2009). The vegetation is composed of shrubs and grasses characterized by warm broadleaf dominant species. The site represents part of the southern Bhutan, which is of data deficient area in terms of birds.

The study has been carried out along the Sunkosh River starting from the confluence of Changchey River, transitory through Sunkosh satellite town till the confluence of Dagachu River in Trashiding geog which passes through undisturbed natural habitat. The river crosses through six different geogs namely Tshangkha and Drujaygang under Dagana District and Barzhong, Rangthangling, Tsholingkhar and Tsirangtoe under Tsirang District. For my study, the area was divided into three different habitats according to general landscape attributes. The study area are divided into three different sites as river confluence, settlement area and undisturbed forest. River confluence is composed of grasses, shrubs and patches of chirpine forest uphill whereas the settlement area consist of human settlement, agriculture land, horticulture crops, roads, etc,. The vegetation structure of undisturbed forest are like bamboo species, warm broadleaved forest and underground vegetation.

The study area under Changchey river confluence ranges from 27°01'17.9" N to 090°04'35.5" E with an altitude range between 325 to 360 masl. Under settlement area, it is 27°00'57.7" N to 090°04'20.5" E and altitude ranges from 299 to 324 masl. The undisturbed forest lies between 27°59'19.6" N to 090°04'28.2" E and altitude ranges from 267 to 299 masl. Compared to forested area (Site 3), river confluence and settlement area was observed as most disturbed due to human activities, stone crushing plant and agricultural activities.

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Figure3.1 Map of the study area

3.2 Materials

The materials used for this research include: - Suunto altimeter for recording altitude at the point count along the river with uniform interval of 200 m. Global Positioning System (GPS) was used for recording latitude and longitude coordinates in the point count and measuring tape for measuring the uniform distance between the point counts. Digital camera (Canon EOS 550D) and reference books on birds was utilized to take images of unidentified bird species for identification, binocular for observation and marker pens to mark the pegs in the plot. Along with the survey data sheet, pencils, eraser and field books were used for recording birds and vegetation data.

3.3 Methods

Owing to the site condition, point count survey method (Hamel et al., 1996) was followed by data collection by taking a walk along the river. Some of the basic methods used in this study (Bibby et al., 1992) was point counts in order to determine abundance by undertaking a bird count from a fixed location for period of 15 minutes. The study was conducted from December, 2015 to March, 2016. A binocular (Olympus) and camera (Canon EOS 5D) was used to confirm the identification of the birds.

Birds were identified to the species level and their taxonomic groups were properly categorized based on Birds of Bhutan by Inskipp et al. (1999). This study was limited to diurnal birds only due to lack of special equipment to detect nocturnal birds. For every bird species the following parameters were recorded: (i) name of the bird; (ii) the number of bird species at every sighting; (iii) habitat types. The Illustration plots was visited twice and the survey was conducted from 5:00 am till 10:00 am and 3:00 pm to 6:00 pm when the birds are more active(Thinh, 2006). The illustration plots are laid out along the river bank at a systematic interval of 200 meters. In total, 30 number of illustration plots (n) are obtained along the river covering 6 kilometers of distance in the entire study area.

The number of birds on the ground, water and overhead resting are recorded within 3600 from each point. Before moving to the next plot, the count lasted for 15 minutes in each plot as supported by (Bibby et al., 1998) stating that longer periods are preferred for multiple species than single species which is usually (5-10) minutes. Upon reaching a point, 2-5 minutes were provided for the birds to settle in case of any disturbances (Bryan et al., 1984). During this time, the number of individuals of each species heard or seen in a circle with a help of camera and binoculars on each point are recorded.

3.4 Data analysis

Compilation and analysis of data was done using Microsoft Excel 2013 and SPSS (Statistical Package for Social Science, version 23.0). SPSS program was also used to produce graphs and figures. The GIS software (Arc GIS, version 9.3) was used for data management, data analysis and production of a simple map (Figure 1).

a. Species composition or species richness: abundance for each species was calculated by summing up the number of individuals recorded in three different types of habitats and in all the illustration plots.

b. Species diversity: was calculated using Shannon diversity index (H’)

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Where “pi” is the proportion of species expressed as a proportion of the total individuals of all species and “Ln” is the natural logarithm. The compiled data was tested for normality to assign appropriate test. The Correlation was performed to determine the relationship between the altitude, habitat types and bird species composition and diversity.

c. Species evenness was calculated using the Shannon’s evenness formula computed as;

EH = H/LnS, where it measures how similar the abundance of different species are in a plot or an area combining species richness (S) and Shannon index (H’)

CHAPTER FOUR Results and Discussion

4.1 Bird Species Composition

A list of 59 bird species were recorded along the three study sites from December to March 2016 (Table 4.1). The population structure pattern in percent have shown that Red-vented Bulbul (Pycnonotuscafer) from the Pycnonotidae family has the highest relative abundance of 15.27% followed by Plumbeous water Redstart (Rhyacornis fuliginosus) from Muscicapidae family with 10.69%. A total of 59 bird species distributed to 30 families were recorded from the study area with an altitude range of 267 to 360 m during the study period. Nineteen families were represented only by one species each. The number of bird species recorded at a single point with uniform plot distance of 200 m varied from 2 to the maximum of 9 species of birds (Figure 4.3). The Bird Species Composition (BSC) in each of the three habitat types varied from 19 to 36 species. The highest bird species composition was recorded in the settlement area with 36 species followed by undisturbed forest with 32 species. River confluence was recorded as the lowest in bird species composition with 19 bird species (Figure 4.1).

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Figure 4.1. Bird species composition in three study sites

The dominant family of birds are Muscicapidae contributing to 9 species (15.25%), followed by Pycnonotidae, Sylviidae and Timalidae contributing 5 species each (8.47%), Dicruridae and Nectariniidae contributing 3 species (5.08%). Sittidae, Picidae, Megalaimidae, Campephagidae and Alcedinidae contributing 2 species each (3.39%). Apodidae, Ardeidae, Bucerotidae, Charadriidae, Chloropseidae, Columbidae, Cuculidae, Hirundinidae, Laniidae, Motacillidae, Paridae, Passeridae, Phalacrocoracidae, Phasianidae, Psittacidae, Rhipiduridae, Stumidae, Trogonidae and Upupidae contributes 1 species each in the community comprising of 1.69%.

Table 4.1. Total bird species recorded in the entire study area

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Figure 4.2. Representing IUCN status of the bird species

During the survey period, White-bellied Heron was recorded which is listed as critically endangered species under the International Union for Conservation of Nature Red list followed by three near threatened bird species and 55 least concerned species. Alexandrine Parakeet, Great Hornbill and River Lapwing falls under the near threatened status as per the IUCN Red list (Figure 4.2).

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Figure 4.3 Number of bird species against each family in the entire study areas

Habitat types and bird species composition were positively correlated and it was significant (r = .500, p < .01). The differences were statistically significant and higher bird species composition was recorded in the settlement area. The higher bird species composition in settlement area may be associated with varied habitats as Thakur (2013) reported higher bird species composition in areas associated with varied types of habitat such as presence of marshes, ridges, forest glades, human settlements, agricultural land and streams cutting through the valleys. Such features mentioned by Thakur (2013) were observed in the area referred herein. Broadly, areas with higher levels of energy-related variables such as primary productivity, potential evapotranspiration, solar radiation, temperature, and rainfall tend to have higher species richness (Brooks et al., 2001).Lameed (2011) presented similar outcome in their study of water bird diversity species composition which was said to be greatly influenced by fringe vegetation of wetland, suitable site for roosting, nesting, feeding, and climatic variation, aquatic macrophysics, which provide greater habitat heterogeneity for the water birds.

4.2 Bird Species Diversity

The overall birds observed along the Sunkosh river were 392 (N = 30). The bird species diversity (BSD) in each of the three habitat types varied from 2.53 to 3.16 according to Shannon diversity index (H’). The highest bird species diversity was recorded in undisturbed forest with 3.16 followed by settlement area with 3.05. River confluence was recorded as the lowest bird species diversity according to Shannon’s diversity index with 2.53 (Figure 4.4). Bird species diversity and habitat types were positively correlated and it was significant (r = .500, p < 0.01). The differences were statistically significant and higher bird species diversity was recorded in the undisturbed forest area. The study of bird species diversity and its distribution become important not only for knowledge but also for conservation purposes as birds has been used as ecological indicators (Rittiboon and Karntanut, 2011). Shannon-Wiener Index (H‟) most commonly used index in ecological studies range from 0 to 5, usually ranging from 1.5 to 3.5. Kerkoff (2010) similarly defines the diversity index stating typical values are generally between 1.5 and 3.5 in most ecological studies, and the index is rarely greater than 4.

Undisturbed forest site with bird population of 143 (n = 10) birds was considered as richest site as compared to settlement which support 137 (n = 10) birds and river confluence with 113 (n =10) birds. It is because community dominated by one or two species is considered to be less diverse than one in which several different species with a similar abundance (Jame and Rathbu, 1981). The highest diversity at the undisturbed forest could be due to the fact that diversity of wetland component and the adaptation of different aquatic avian to exploit the resources of wetland ecosystem could be reason behind for the highest diversity. Vegetation types and abundant of food resources also play equal role in habitat preference by bird species. Similar finding was reported by (Lameed, 2011; Zakaria et al., 2009).

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Figure 4.4. Bird species diversity index (H') in the three study sites

The Shannon diversity index (H’) ranges from 2.53 to 3.16 (Figure 4.4). The slight difference in bird species diversity between the three habitat types could be due to short study period and similar vegetation structure according to Waterhouse et al. (2002) as they found out that bird species diversity did not differ significantly between different habitats due to similar vegetation structure. This finding is therefore in line with the findings of most of the past studies conducted on birds in relation to altitude. For instance, Chettri et al. (2001) who conducted a study along the altitudinal gradient following a trekking corridor in Sikkim Himalaya found that bird species diversity showed strong and significantly negative relationship with elevation. Similarly, an investigation made by Thakur (2013) also observed a presence of continuous decrease in diversity with the increase in altitude. The overall diversity in the study area as computed using Shannon diversity index was 3.41.

4.3 Relationship between altitude and BSC, BSD, SE

As indicated in the Table 4.2, bird species diversity (H’) is negatively correlated to altitude (r = -.826; p = .000) within the significant level of 0.01. This indicates that the bird species diversity decreases as the altitude increases and vice versa. The similar negative correlation was also determined between the altitude and bird species evenness (r = -.865; p = .000) and (r = -.617; p = .000) for bird species composition.

Table 4.2. Correlation between Altitude, BSC, BSD and SE

Abbildung in dieser Leseprobe nicht enthalten

Altitude affects bird species distribution and diversity in the mountainous region. Elevation creates microclimate which in turn determines temperature, soil characteristics and vegetation type of the given environment (Waterhouse et al., 2002). This is affecting the distribution and diversity of bird species directly or indirectly by limiting availability of the requirement and energy into the ecosystem. Ecological studies show that lower altitude has more bird species than higher altitude while some species are restricted to certain zones and others occurring throughout the altitudes (Jankowski et al., 2009).

The introduction of fertilizers and regular maintenance in settlement areas may also increase primary productivity (Mooney and Gulmon, 1983). In contrast, more intense development, such as office parks or business construction, could decrease the amount of resources available to birds, as construction removes substantial areas from primary production, and landscaping becomes limited to the hardiest ornamental species, which are often exotic (Whitney and Adams, 1980). A similar pattern of addition and then deletion of a resource can be seen in the amount of edge habitat available in the different sites. Moderate levels of development may fragment formerly continuous habitat, increasing the amount of edge habitat available. However, edge habitat will eventually decrease with increasingly severe urbanization, as all native habitat is eliminated with development (Godron and Forman, 1983).

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Details

Title
Bird diversity and distribution along the Sunkosh River, Tsirang and Dagana District in southern Bhutan
College
Royal University of Bhutan  (College of Natural Resources)
Course
Bachelors in Forests Science
Grade
83
Author
Year
2016
Pages
47
Catalog Number
V347025
ISBN (eBook)
9783668365346
ISBN (Book)
9783668365353
File size
1606 KB
Language
English
Tags
bird, sunkosh, river, tsirang, dagana, district, bhutan
Quote paper
Sonam Tobgay (Author), 2016, Bird diversity and distribution along the Sunkosh River, Tsirang and Dagana District in southern Bhutan, Munich, GRIN Verlag, https://www.grin.com/document/347025

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Title: Bird diversity and distribution along the Sunkosh River, Tsirang and Dagana District in southern Bhutan



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