Bird Diversity in the sharavathi river basin
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Bird Diversity in the SHARAVATHI RIVER BASINSudhira H. S. and Ramachandra T. V.Energy and Wetlands Research Group Centre for Ecological Sciences Indian Institute of Science, Bangalore-12, India Phone: 080- 3600985 / 293 3099 / 293 2506 Fax: 91-80-3601428 / 3600085 /3600683{CES-TVR} Email: cestvr@ces.iisc.ernet.in cestvr@hamsadvani.serc.iisc.ernet.in hssudhira@yahoo.com sudhira@ces.iisc.ernet.in Aquatic and terrestrial conditions combine to form 'wet-lands', one of the most complex ecosystems in the world. The environmental characteristics within a wetland are determined largely by hydrologic processes, which may exhibit daily, seasonal or long-term fluctuations, in relation to regional climate and geographic location of the site. These in turn produce a great range of wetland types globally, majority of which have extremely variable conditions in many habitats, which they contain. As a consequence, the variety of living organisms, adapted to the different wetland habitat tends to be high, with all major groups of plants and animals present. The Convention on Biological Diversity's Article 7 on 'Identification and Monitoring' emphasises identification and monitoring of components of biological diversity and processes or categories of activities, which have adverse impacts on biological diversity, and maintenance of data derived from these activities. The bird diversity study was taken up in the Sharavathi River basin, prone to habitat transformation due to dam construction for hydro-electricity generation. As part of the cumulative impact assessment exercise, a detailed study was undertaken to determine the habitat status. This paper brings out the study on bird diversity estimation using Shannon’s index in the catchment area. The data collection was done using the line transect method in nine localities of the study area. The localities are classified chiefly as wetlands and terrestrial habitats. Other statistical analyses carried out on the data are presented in the paper. The study was successful in estimating the diversity index using the Shannon's index as well as in finding the evenness of the habitat. An important observation made by the study was that the order Passeriformes dominated the terrestrial habitat. The study also revealed that the wetlands had a better distribution of birds. This could be inferred from the fact that unlike the terrestrial habitat, Passeriformes and Ciconiiformes dominated wetlands, suggesting that these ecosystems have more diversity than terrestrial habitats. During the sampling period, 73 species were identified but a total of 125 species were sighted including opportunistic surveys. Of the 125 species four are endemics and one endangered species. In the wake of infrastructure development initiatives in the region the endangered bird species mostly found in the undisturbed evergreen forests is threatened by the loss of habitat. Effective conservation strategies in ensuring the continued survival of the endemic and endangered bird species through ecologically sound development initiatives are to be evolved in this regard. INTRODUCTION India has a rich plant and animal diversity. Complexity and diversity are the new frontiers of science (Gadgil, 1996). The most significant challenge before science today is in understanding complex systems with a great diversity of behaviours in space and time. Birds show enormous diversity and complexity. They are one of the most distinctive classes in the animal kingdom, characterised by their ability to fly. They can be defined as feathered bipeds (Ali, 1998). They are warm-blooded vertebrates, highly mobile and found from snow-capped mountains to deserts to seas and various types of habitats. When monitoring habitat transformations, bird communities could give valuable information. A variety of development interventions lead to these transformations and hence the objective is to appraise them in terms of biodiversity values. Though bird communities are less sensitive to the rapid habitat changes (Pramod et al, 1997), the bird diversity indicates the habitat quality of the area. The term "diversity" refers to the number of species living in a designated area. The ratio between the number of species and the total number of individuals in a community is termed as species diversity. It is related to the stability of the environment, varying among different communities and is of great importance in assessing the extent of damage done to natural systems by anthropogenic activities. According to Magurran (1988), there are two main areas in which diversity measures have potential application. These are in conservation, indicates that species rich communities are better than species poor communities, and in environmental monitoring where the adverse effect of pollution will be reflected in a reduction in diversity or by any change in the shape of the species abundance. In both areas, diversity is used as an indicator of the ecosystem’s well being. Biodiversity lies at the level of the genotype, the hereditary or genetic make-up. The variability, geographic dispersion and biological richness of wetlands globally mean that they contain a tremendous pool of genetic resources. This genetic diversity is important for a variety of reasons: it determines the ability of individuals and populations to adapt to changing environmental conditions, such as global warming or new diseases; it is essential for the continuing evolution of various species; it provides the basis for the selection and production of new resource organisms; it is also important for maintaining the distinctiveness of plants and animals in different locations. Loss of wetland habitats, which contain so much of the world's plant and animal biodiversity, thus endangers the genetic resources on which the future prosperity of mankind depends. Convention on Biological Diversity's Article 7 on 'Identification and Monitoring' calls for identification and monitoring of components of biological diversity and processes, which have adverse impacts on biological diversity, and maintaining data derived from the preceding activities. The species diversity and high production levels of wetlands support even more diverse animal communities. The vegetation distribution patterns and water level fluctuations make a range of continuously changing wetland habitats available at different times of the year to aquatic, terrestrial and arboreal animals. Decline in the wetland quality will impact associated systems: loss of nursery habitat could reduce fishery yields or loss of a wetland on a flyway could disrupt waterfowl migrations, threatening the capacity of individual birds to reproduce and eventually the survival of populations or species. Many wetlands have abundant food resources (both living plants and their decomposition products) that can be utilized by species other than the permanent residents. Entry by 'visitor species' serves to increase the diversity of animals that may be seen in wetlands from time to time. Literature ReviewThe study area is located in the famous Western Ghats region, which has recorded 586 bird species. Various studies have been done under the Western Ghats Biodiversity Network (WGBN). Currently, under Project Lifescape (supported by the Indian Academy of Sciences, Bangalore), enormous efforts are being put to study the region and document the diversity. Pramod et al (1997) studied the bird assemblages to determine their ubiquity and hospitality. Another study undertaken by Pramod et al (1997a), assigned conservation values to bird species based on the readily available information on their geographical range, habitat preference, endangerment and taxonomic distinctiveness. Apart from these detailed studies, there is an unpublished manuscript on the trek to Muppane and Kanoor, reporting 74 species in 4 days. 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). Many wetlands provide habitat for other important faunal components, serving as resting and feeding stations along migratory flyways for ducks, waders and shorebirds which benefit from the diversity of food organisms (Peter, 1996). The seasonal influx of passage migrants serves to increase the biodiversity of many wetland sites. In their study of coastal wetland habitats in Surinam, South America, Swennen and Spaans (1985) found more than 75% of the foraging waterfowl were migrants of northern origin, with only a minority being local resident species. For the eight families studied in an area of just 736 ha of these rich and varied coastal wetlands, they found 15,678 waterfowl belonging to 40 species dependent on the wetlands during the tropical part of their life cycle. This example shows that the migratory component of the bird life of wetlands is important, not only in terms of species diversity but in numbers of individuals. Similarly, the 24,000 ha Cache River Basin in North America provided wintering habitat annually for nearly 200,000 Canada Geese Branta canadensis, 35,000 Snow Geese Anser caerulescens and 26,000 ducks which would breed further north (USFWS, 1994). 'Quantifying quality' is fundamental to any conservation assessment of an organism or habitat (Daniels, 1989). The influence of habitat reduction or transformation on the birds of the catchment has to be understood. Disappearance of one recorded species of bird is probably the best clue. Preston (1979) has however observed that birds may be merely overlooked while sampling in the field. Single observers have a 50% chance of missing an individual bird while surveying. Species existing in small numbers and those, which are cryptic, are easily overlooked. Any conclusion regarding change in the avifauna based on a comparison between two observers' results, especially over a period of time, must be carefully analysed before drawing any inference. METHODOLOGY Methods of population estimation differ according to the objective of study as well as category of birds’ under study. Population estimates in terms of birds per unit area are more difficult to achieve than diversity indices. Diversity indices allow comparison between years, seasons or areas without giving an idea of the actual number of birds involved. Being an extremely mobile group of organisms with varied kinds of local and continental migratory behaviour it is very difficult to estimate and monitor bird population. The observation was carried out along riverbeds in case of wetlands. The term 'wetlands' throughout the discussion refers to reservoir and water spread area. Here, the sightings were recorded on the bank of the river courses within a radius of 20 meters. In case of terrestrial habitats, observation was done along transects which were about half a kilometer to one kilometer in length. Information such as time of sighting of species, number of individuals, place of sighting and grouping behaviour was recorded. STUDY AREA The Sharavathi river basin is prone to habitat transformation due to the construction of the dam for hydro-electricity generation at Linganamakki. The Sharavathi river basin upstream of the Linganamakki dam is about 2000 square kilometers and is located in the Western Ghats, the biodiversity hot spot. Linganamakki dam is built across river Sharavathi for hydroelectric power generation. With the construction of the dam, forests and lands as well as the Hire Bhaskar or Madenur dam got submerged. The Madenur dam was built in 1952 for power generation at the Mahatma Gandhi Hydroelectric station. Since its submergence, Linganamakki dam is used for power generation. Figure 1 shows the map of the study area with varied vegetation types along with sampling locations. The study was undertaken in the catchment area along the river courses of Sharavathi, Haridravathi, Mavina Hole, Nagodi Hole and Yenne Hole. The observation was also done at China gate, the entry point of water to the hydroelectric power station. Apart from observation along wetlands, terrestrial areas were also covered. The terrestrial habitats were of moist deciduous to semi-evergreen type. Table 1 shows the different localities, time spent, longitude, latitude and altitude. 
Figure 1: Location of the Study Area showing the Sampling Locations Table 1: Location at all sampling stations
RESULTS AND DISCUSSION The first part of the data analysis was computation of the ratios of number of sightings by number of species by number of individuals. This was done initially for ten minutes and later converted to per minute. Mean, standard deviation and standard error were calculated. The total number of individuals of all species was calculated. The proportion of number of individuals of all species is tabulated. Further, the list of cumulative species identified is tabulated separately for wetlands and terrestrial habitat. With this, a curve is plotted against time to get the species accumulation curve. Finally, a list of bird species identified is prepared. The time spent and number of species seen at each locality is tabulated with the number of species seen per minute and hour. The ratio of number of sightings to number of species to number of individuals was compared (Table 2). All these were normalized to one minute. Here the average of species seen per minute is more in the case of wetlands than the terrestrial habitats with 0.540 and 0.373 values recorded respectively. The number of species seen per minute for the combined habitat type was 0.453. The standard deviation and standard error for number of species seen per minute, number of individuals seen per minute and the number of sightings per minute were also better for wetlands than the terrestrial habitat. Table 2: Summary of Observation along the Catchment area Wetlands
Terrestrial
Combined
NOTE: NSGFTM - No. of Sightings for ten minutes NSGPM - No. of Sightings per minute NSPFTM - No. of species for ten minutes NSPPM - No. of species per minute NINDFTM - No. of individuals for ten minutes NINDPM - No. of individuals per minute A table of time spent at all the localities was made, which is as shown below. From Table 3, it can be seen that more time was spent at Muppane and Sampekai as compared to other localities. At Sharavathi and Sharmanavati 77 and 70 minutes was spent while at Haridravati 30 minutes was spent. The species seen per hour is highest in case of Nagodi Hole, which is 27.426 species seen per hour and 24 species per hour at R. Haridravati and China gate. But more number of species sighted during observation was at Sampekai with 37 species in 130 minutes. Table 3: Time Spent at all Localities
The cumulative number of species sighted during the observation is prepared separately for wetlands and terrestrial habitats. The species accumulation curve was obtained by plotting a graph of cumulative number of species against time. It can be seen from Figure 2, that it took 310 minutes to sight 48 species in the terrestrial habitats and 270 minutes to sight 49 species in wetlands. More species in less time was found in the wetlands than the terrestrial habitats as evident from the Species time curves from Figures 2 and 3. Further from Figure 2 it can be seen that the curve increases constantly with time, suggesting that more species could be found if more time was spent in the habitat. But in Figure 3, though the curve increases constantly with time, in the last 30 minutes of observation no new species was recorded. Hence, the curve became horizontal. If more time was spent here there could be an increase in the number of species seen. The table of Shannon’s indices and evenness (Table 4) were calculated for both types of habitats as well as grouped data are shown below. It can be seen that diversity is lesser in terrestrial than in the wetlands. However, when the data is grouped the diversity in total is more than the individual diversities. The evenness is also calculated for both type of habitats as well as the grouped data. The evenness is slightly higher for wetlands than the terrestrial habitat type, but the combined value is more with 1.717. Table 4: Shannon’s Indices and Evenness
The evenness calculated for terrestrial habitats and wetlands are 0.390 and 0.393 respectively. The evenness of the combined habitat type is more, suggesting the combined habitat is relatively more even. CONCLUSION The study shows that the diversity indices give a picture of the species diversity of the habitat, which is controlled by the presence of rare species in the sample. However by pooling the results of sampling and opportunistic survey carried out, considerable hypothesis was made on the distribution of birds in the habitat. During the sampling period, 73 species were identified but a total of 125 species were sighted during the study period. An important observation made by the study was that the order Passeriformes dominated the terrestrial habitat. The study also revealed that the wetlands had a better distribution of birds. This could be inferred from the fact that unlike in the terrestrial habitat, wetlands were not only dominated by Passeriformes but also Ciconiiformes; suggesting their higher diversity. The species time curve for the terrestrial habitats in the catchment area suggested more time to be spent, as the curve remained on the increase. However considering the bird diversity alone as the ecosystem indicator would require more thorough statistical analyses to be evidently considered as ecosystem indicator. This study explored the possibility of considering the bird diversity as ecosystem indicators. REFERENCES: Ali, S., (1998). “The Book of Indian Birds”, 12th Centenary Edition, Bombay Natural History Society, Mumbai and Oxford. Galli, A. E., Leck, C. E. and Forman, T. T., (1976). "Avian distribution patterns in forest islands of different sizes in central New Jersey", The Auk, 93: pp. 356-364. Mac Arthur, R. H., (1965). "Patterns of species diversity", Cambridge Philos. Soc. Biol. Rev. 40: pp. 510-533. Madhav Gadgil., (1996). “Documenting Diversity: An Experiment”, Current Science, 70, pp. 36-44. Magurran, A., (1988). “Ecological Diversity and its Measurements”, Croom-Helm, Australia. Michael, P., (1983). “Ecological Methods for Laboratory and Field Investigation”, McGraw-Hill Publishing House. Peter, R. B., (1996). "Wetlands and Biodiversity", Wetlands, Biodiversity and Ramsar Convention, The Ramsar Library. P. Pramod, R. J. R. Daniels, N. V. Joshi and Madhav Gadgil., (1997). “Evaluating Bird Communities of Western Ghats to plan for a Biodiversity Friendly Development”, Current Science, 73: pp. 156-162. P. Pramod, N. V. Joshi, Utkarsh Ghate and Madhav Gadgil., (1997a). “On the Hospitality of Western Ghats Habitats for Bird Communities”, Current Science, 73: pp. 122-127. Preston, F. W., (1979). "The invisible birds", Ecology, 60: pp. 451-456. Pyrovetsi, M. and Givelli, A., (1988). "Habitat use by waterbirds in Prespa National Park, Greece", Biol. Conserv. 45: pp. 135-153. Rafe, R. W., Usher, M. B. and Jefferson, R. G., (1985). "Birds on reserves: the influence of area and habitat on species richness", J. Appl. Ecol., 22: pp. 327-335. Swennen, C. and Spaans, A. L., (1985). "Habitat use of feeding migratory and local Ciconiiform, Anseriform and Charadriiform birds in coastal wetlands of Surinam", Le Gerfaut, 75: pp. 225-251. Terborgh, J. W., (1973). "On the notion of favourableness in plant ecology", Am. Nat. 107: pp. 481-501. USFWS., (1994). "A joint venture proposal for designation as Wetlands of International Importance: The Cache River and Cypress Creek wetlands area of Southern Illinois", Report of the U.S. Fish & Wildlife Service and Illinois Department of Conservation. R. J. R, Daniels, (1989). A conservation strategy for the Birds of the Uttara Kannada District. Ph. D Thesis. Indian Institute of Science. Bangalore. List of Bird Species Identified in Terrestrial Habitat
List of Bird Species Identified in Wetlands
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The list of bird species sighted during the observation along terrestrial and wetlands was tabulated. The list is given in the appendix. A total of 73 species was sighted during the sampling in the catchment area. Interestingly 49 species was sighted in both terrestrial and wetland type of habitats separately. It was found that in the terrestrial habitats, the 48 species sighted comprised 22 families and 10 orders. Of them, Passeriformes had the majority with 11 families and 33 species, which accounts for 67.34% (more than 2/3rd) of the total species sighted during the study, suggesting its dominance in the terrestrial habitat. In the wetlands, there were 27 families and 8 orders, of which 9 families belonged to Passeriformes and Ciconiiformes each. Interestingly, unlike the terrestrial habitat, Passeriformes and Ciconiiformes do not singly dominate the wetlands. The number of families is more in wetlands than the terrestrial habitat, which suggests the higher diversity of wetlands. It can also be implied that the habitat is more balanced.