pg. 1

I INTRODUCTION

The east coast of India, especially Tamil Nadu region is important to

waterbirds as many important wetlands such as Point Calimere swamps,

Pichavaram and Muthepet mangroves, etc. are situated here. These wetlands

are especially important in the context that they serve as wintering areas for birds

as appreciable number of many species of birds annually migrate from Arctic

Siberia to wintering grounds in India en-route Australia (Sampath &

Krishnamurthy 1990). Myers (1983) also suggested that such areas are critical

for continuance of migration and ultimately for the survival of many waterbirds.

Wetlands are the “area of marsh, swamp, pebbles or water, whether

natural or artificial, permanent or temporary, with water that is static or flowing,

fresh, brackish or salty, including areas of marine water, the depth of which does

not exceed six meters” as defined in the text of the Convention on Wetlands of

International Importance especially as Waterbird habitats known as the Ramsar

Convention.

Wetlands support highly valuable pools of biodiversity and genetic

resources, but unsustainable development is threatening the biowealth and even

pg. 2

causing species extinction (Khan 2000). These are fragile ecosystems that are

susceptible to changes even with little change to the composition of their biotic

and abiotic factors. In recent years, there has been increasing concern over the

continuing degradation of world’s wetlands (Prasad et al. 2002; Pattanaik et al.

2008; Sandilyan et al. 2008; Kannan & Pandiyan 2010). Wetlands sustain all life

and perform useful functions in the maintenance of ecological balance.

Over 50% of wetlands in the world have been lost in the past century, and

the remaining wetlands have been degraded to different degrees because of the

adverse influences of human activities (Fraser & Keddy 2005). The loss and

degradation of wetlands has negatively affected waterbirds, which depend on

wetland habitats. How to provide high quality habitats for waterbirds through

effective management is a critical issue in waterbird conservation (Weber & Haig

1996; Erwin 2002; Taft et al. 2002).

One of the best known functions of wetlands is to provide a habitat for

birds (Sampath & Krishnamurthy 1990; Nagarajan & Thiyagesan 1996). Humans

have known of the link between birds and wetlands for thousands of years.

Prehistoric people drew pictures of birds and wetlands on cave walls, scratched

them on to rocks and used them in the design of artifacts. Wetlands are

important bird habitats and birds use them as migratory resorts for breeding,

pg. 3

nesting and rearing youngs. Birds also use wetlands as a source of drinking

water and for feeding, resting, shelter and social interactions.

The geographic location of a wetland may determine how and when birds

will use it or use adjacent habitat. In the northern latitudes or at high altitudes,

some wetlands are covered with ice in the winter and are temporarily “out of

service” for birds adapted to a water environment. Birds that eat fish, aquatic

invertebrates or submerged vegetation cannot forage for food because of the ice

cover. Some wetlands are on the migration path of waterbirds and provide

stopover locations for travelling birds. Birds’ use of wetlands during breeding

cycles ranges widely. Some birds depend on wetlands almost totally for breeding

and feeding or shelter. Birds that need functional access to a wetland or wetland

products during their life cycle, especially during the breeding season are known

as “wetland dependent”. Other birds use wetlands only for some of their needs or

they might use both wetland and upland habitats (Ali 2005).

The Central Asia flyway covers the areas used by species of the birds with

the main migratory routes through Central Asia. The flyway area extends through

21 countries from Arctic Ocean in the North to the Indian Ocean in the South. It

overlaps with both the African-Eurasian flyways in the West, and the West Asian-

Australasian flyways in the East. This intra-continental flyway includes many

important wetlands, which are actively and often unsustainably exploited by man.

pg. 4

The region holds crucially important populations of some waterbird species,

including a number of those globally threatened species. Many countries along

this flyway have developing economies with inadequate allocation of resource for

research and conservation (Wetland International 2004).

Migratory birds are found during October-March in large range of countries

of Middle, Central and Southern Asia. Countries of primary importance for

wintering are India, Pakistan, Sri Lanka and Iran in South Asian flyway of

migration (Ali 1981; Balachandran 1998; Hussain 1991). The population of

migratory birds has undergone significant and rapid decline in the second half of

the 20th century and is considered ongoing. Many species are qualifying for

special attention in the list of Globally Threatened Bird Species and in the IUCN

Red List. The reasons for the ongoing decline are unknown and it is even

unclear what the main threats are at wintering grounds. No practical measures

have been taken so far. There is a need for a framework for conservation with

measurable objectives and management options for migratory birds

and their habitats.

The Ministry of Environment and Forests has identified about 2,175

wetlands in India covering about 4.1 million hectares (Alfred & Nandi 2000), of

which, 93 are major wetland sites and 19 are Ramsar sites, the Wetlands of

pg. 5

International Importance (Asian Waterbird Census 2001). Many of these

wetlands are wintering grounds for migratory birds.

There are 465 Important Bird Areas in India (Islam & Rahmani 2004).

Many of them are wetlands and host important migrant and resident water birds.

Chilka Lake in Orissa hosts 211 bird species, of which, 86 are waterbirds, and

the lake is known for ducks and waders (Zoological Survey of India 1995;

Balachandran el al. 2003). Keoladeo National Park, Bharatpur hosts at least 350

bird species which include the Siberian Crane (Grus leucogeranus) and ducks

(Vijayan 1991).

Great Rann of Kutch in Gujarat is known for flamingos (Islam & Rahmani

2004). Wular Lake in Jammu and Kashmir is known for ducks and geese. A total

of 110 waterbird species have been recorded in Point Calimere, out of which 34

are migratory. The commonest groups are the flamingos, ducks, waders, gulls

and terns (Sugathan 1982). Pulicat Lake in Andhra Pradesh and Tamilnadu is

known for flamingos, ducks and waders (Daniel 2004).

According to Sampath & Krishnamurthy (1990) although information on the

population structure of waterbirds of Eastern Asia and Pacific regions are

available in plenty, only few studies such as by Ali (1981, 1986), Ali & Hussain

(1981, 1982), Hussain et al. (1984) and Ali and Sugathan (1985) are available on

pg. 6

their population structure in Indian situations and only few reports (Nagarajan

1990; Nagarajan & Thiyagesan 1996; Oswin 1999; Divakaran 2000; Pandiyan

2002; Sridharan 2003; Kannan et al. 2008; Bhat et al. 2009; Sandilyan 2009;

Nagarjuna et al. 2010).

There are about 242 wetland bird species and 67 wetlands support bird

species among the 1300 species of birds recorded in the Indian subcontinent

(Grimmett et al. 1999; Manakadan & Pittie 2002). Of these 125 are migrants,

among which 102 species are winter migrants, 10 are summer migrants and 3

are passage migrants. Approximately 12% of Asian birds are globally threatened

(Arun Kumar et al. 2003). Wetland birds comprise about 10% of the globally

threatened species and 20% of Asian threatened species. About 34 of the

wetland birds are globally threatened species, 34 are critically endangered and

one conservation dependent (Manakadan & Pittie 2001). Unfortunately, many

ornithologically important wetlands all over the world are threatened and

waterbirds are under pressure from increasing human population, socio-

economic activities and man-induced adverse natural phenomena (Jagtap 1985;

Parnell et al. 1988; Hussain 1991; Balachandran 1993; Arun Kumar et al. 2003).

Such being the case, it is important to see that the wetland habitats of various

waterbirds are properly conserved through scientific management. Sound

management of such habitats is only possible by using available information on

existing habitat components.

pg. 7

Many studies have been conducted on the wetland bird species in India,

but little information exists on the assemblage structure as a whole. Assessing

the wetland assemblage would provide information on the common and rare

species, migratory behaviour and habitat usage. This would be important for the

conservation of wetland biodiversity and for assessing threats to particular

species and to ecosystems.

The fluctuations of waterbird populations and variations in species diversity

and density serve as management tools for wetlands. The species density,

diversity, richness and relative abundance of waterbirds depend upon wetland

characters such as size, water level, quality of water, availability and distribution

of food resources (Finlayson et al. 1992; Montes et al. 1995; Caziani & Derlindati

2001; Verboom et al. 2001; Parsons et al. 2002; Paracuellos 2006) and the

abiotic changes in the wetlands (Jaksic 2004; Lagos et al. 2008).

The importance of abiotic variables has long been recognized in the

habitat utilization of birds by several authors (Patterson 1976; Murphy et al.

1984), only recently have investigators concentrated on finding out how particular

abiotic factors affect waterbirds (Nagarajan & Thiyagesan 1996; Takekawa et al.

2006). Considerations of water quality is important in waterbird habitat evaluation

because a host of interacting physical and chemical factors can influence the

level of primary productivity in aquatic systems and thus influence the trophic

pg. 8

structure and total biomass throughout the aquatic food web (Wetzel 1975).

Indeed a relationship between water quality and waterbirds had already been

indicated by several studies (Patterson 1976; Murphy et al. 1984; Nagarajan et

al. 2008). It has been inferred that the physiochemical characteristics of the water

largely determine the water bird community of aquatic habitats, primarily by their

direct and indirect impact on the availability and abundance of the birds’ prey

(Nagarajan &Thiyagesan 1996).

The weather conditions such as rainfall, temperature, humidity and wind

velocity have been reported to influence wader densities (Goss-Custard 1985;

Briggs & Holmes 1988; Nanda Kumar et al. 2009). Various physico-chemical

parameters of water such as salinity, pH, electrical conductivity, dissolved

oxygen, turbidity, hardness, water depth and levels of nutrients such as nitrates,

nitrites, phosphates, chloride have been reported to influence the waterbirds’

density and diversity (Powell 1987; Duckglass & Relmchan 1988; Sampath &

Krishnamurthy 1990; Gibbs et al. 1991; Vickery 1991; Valasquez 1992; Bethke &

Nudds 1993; Nagarajan & Thiyagesan 1996; Paracuellas 2006;

Sonal et al. 2010).

Salinity plays a significant role in aquatic environments, especially in

variable saline habitats such as estuaries, swamps, and lagoons. Organisms

which live in a saline environment are sensitive to changes in its salinity

pg. 9

(Nagarajan et al. 2008). The variations in the salinity gradient in an environment

could affect the distribution, growth and survival of organisms (Akberali et al.

1983; Westerbom et al. 2002). It is also well established that the changes in the

salinity could influence the population of plankton, benthic organisms and macro

invertebrates in aquatic ecosystems (Britton & Johnson, 1987) which are the

major food sources for top level predators including birds.

pH might be considered an indicator of overall productivity that can cause

habitat diversity (Minns 1989). pH of wetlands is an important factor in

waterbirds’ habitat quality assessments as correlation between pH

and waterbirds’ distribution had been reported earlier (Vickery 1991; Gibbs et al.

1991; McNicol & Wayland 1992). According to Bendel & McNicol (1995) pH

levels could alter the invertebrate and other prey types and thereby the feeding

habits and food selection of waterbirds. The pH had been shown to have

significant correlations with species richness of phytoplankton (Almer et al. 1984;

Parker et al. 1992). A significant relationship between waterbirds use of wetland

and their pH has been reported by coastal wetlands of Tamil Nadu, India by

Nagarajan & Thiyagesan (1996) and Pandiyan (2002).

Relationships between the variations in the waterbird population and the

dissolved oxygen levels and alkalinity and magnesium hardness had been

reported previously as well (Murphy et al. 1984; Sampath & Krishnamurthy

pg. 10

1990). Nitrites and other nutrients are regarded as important limiting factors for

various aquatic organisms. It is well documented that nutrients play a vital role in

the productivity of many aquatic ecosystems (Nilson & Nilsson 1978; Richardson

et al. 1978; Stauffer 1991). Levels of nitrites and phosphates in the Pichavaram

wetlands significantly influenced the density of waterbirds (Nagarajan &

Thiyagesan 1996). Levels of nitrites and other nutrients were reported to be

important variables that influenced the avifaunal characteristics in the shorebirds

of the Islands of Gulf of Mannar (Divakaran 2000). The same was also reported

by Pandiyan (2002) in the tidal flats of Cauvery deltaic region of Southern India.

Since the aquatic habitats are dynamic in nature, the level of the

substratum (water) fluctuates rapidly within a day due to tide and the annual

variations caused by precipitation and evaporation. Such variation in water depth

largely determines the habitat use of birds (Sayre & Rundle 1984; Poysa 1989;

Rostogi & Pathak 1990). Birds that feed on aquatic habitats use a variety of

foraging techniques from diving (cormorants, shags and pelicans) to mud probing

(plovers and sandpipers). Therefore the wide variation in water depth across the

day and season could influence the population dynamics i.e. density, diversity

and richness of water birds in aquatic habitats. Nagarajan & Thiyagesan (1996)

emphasized that the habitat selection and changes in waterbird population are

primarily influenced not only by prey availability but also by their accessibility,

which in turn is largely influenced by water depth.

pg. 11

Electrical conductivity is a measure of the ionic composition in the waters

and so play a vital role in the release of the nutrients and consequently the

productivity of aquatic ecosystems. The relationship between the electrical

conductivity levels and bird density might be mediated via its influence on the

productivity and faunal composition of the wetland ecosystem. Electrical

conductivity has been reported to have significant correlations with the waterbirds

diversity in the Pichavaram wetlands (Nagarajan 1990) and the tidal flats of

Cauvery deltaic region, Southern India (Pandiyan 2002).

Phytoplankton is the pioneer of an aquatic food chain. The productivity of

an aquatic environment is directly correlated with the density of phytoplankton.

The phytoplankton population in any aquatic system is the biological wealth of

water for fishes and constitutes a vital link in the food chain. They form a bulk of

food for zooplankton, fishes, aquatic birds and other organisms. The

maintenance of a healthy aquatic ecosystem depends on the abiotic properties of

water and the biological diversity of the ecosystem (Harikrishnan et al. 1999).

The phytoplankton and zooplankton are always inversely proportional in an

aquatic environment because the zooplankton feed on the phytoplankton. The

planktonic study is very useful tool for the assessment of water quality in any

type of water body and also contributes to understanding of the basic nature and

general economy of the wetland (Pawar et al. 2006). Phytoplankton studies and

monitoring are also useful for control of the physico-chemical and biological

pg. 12

conditions of the water. Over the last few decades, there has been much interest

in the processes influencing the development of phytoplankton communities,

primarily in relation to physico-chemical factors (Akbay et al. 1999;

Peerapornpisal et al. 1999; Elliott et al. 2002). Although, a voluminous literature

is available on the plankton population of different wetland habitats of India (Mani

& Krishnamurthy 1989; Kannan & Vasantha 1992; Kawabata et al. 1993; Gouda

et al. 1996; Rajasegar et al. 2000; Sukumaran & Das 2001; Ravikumar et al.

2006; Sridhar et al. 2006; Balasingh & Shamal 2007; Periyanayagi et al. 2007;

Balasingh et al. 2008; Saravanakumar et al. 2008; Senthilkumar & Sivakumar

2008; Laskar & Gupta 2009; Rajkumar et al. 2009; Ganai et al. 2010), scanty

literature is available on the Great Vedaranyam Swamp in question. Hence, the

present study determines the phytoplankton abundance in the Great

Vedaranyam Swamp and aims to relate the effects of physico-chemical

parameters on phytoplankton abundance.

Zooplankton plays a pivotal role in aquatic food webs because they are

important food for fish and invertebrate predators and they graze heavily on

algae, bacteria, protozoa and other invertebrates. Zooplanktonic communities are

highly sensitive to environmental variation. Zooplankton are often an important

link in the transformation of energy from producers to consumers (Shastree et al.

1993), due to their large density, shorter life span, drifting nature, high group or

species diversity and different tolerance to the stress and zooplankton are being

pg. 13

used as indicator organisms for the physical, chemical and biological processes

in the aquatic ecosystems (Dadhick & Saxena 1999). Gaikwad et al. (2008)

stated that the species richness and evenness were inversely related to the

zooplankton biomass. Zooplanktonic communities have been investigated in

numerous water bodies of India (Gajbhiye & Desai 1981; Gowing & Wishner

1982; Vijayakumar & Sarma 1988; Sastry & Chandramohan 1995; Ramiah et al.

1996; Suresh & Mathew 1997; Rao & Kumari 2002; Santharam & Perumal 2003;

Damotharan et al. 2010; Salve & Hiware 2010) but little is known in the Point

Calimere Wildlife Sanctuary. Accordingly the present study determines the

zooplanktonic abundance in the Great Vedaranyam Swamp and relates the

effects of physico-chemical parameters on zooplankton abundance.

Macrobenthos are the important group of organisms which are found in

sediments beneath the water column, act as a key component in any aquatic

ecosystem. Macrobenthic invertebrates are also useful bio-indicators providing a

more accurate understanding of changing aquatic conditions than chemical and

microbiological data, which at least give short-term fluctuations (Ravera 1998,

2000; Ikomi et al. 2005). Waterbirds acquire important nutrients by feeding on

benthic macro-invertebrates the availability of which is influenced by

physiochemical variables such as water depth and water chemistry. Benthic

invertebrates have been found to be the primary foods of waterbirds (Reeder

pg. 14

1951; Rundle 1982), and these invertebrates have also been found to strongly

influence the distribution (Colwell & Landrum 1993) and feeding behavior of

waterbirds (Murkin & Kadlec 1986). Waterbirds have been reported to reduce the

density of benthic invertebrates (Mercier & McNeil 1994) and to select habitats

with higher densities of benthic invertebrates (Safran et al. 1997). Many

investigations have been carried out on the abundance and distribution of

macrobenthos in India (Ansari et al. 1986; Vijayakumar et al. 1991; Sunilkumar

1995; Anbuchezhian et al. 2009; Mahapatro et al. 2009; Varadharajan et al.

2009; Magdoom et al. 2010; Siraj et al. 2010) but not many correlations between

bird’s density and macrobenthos abundance have been made earlier and hence

this aspects formed one of the objectives in the present investigation.

A perusal of literature on the ecological aspects of the Great Vedaranyam

Swamps of the Point Calimere Wildlife Sanctuary has revealed that only a few

works have been done earlier. Sampath (1989) has studied the ecology of

shorebirds (Aves: Charadriiformes) in the Great Vedaranyam swamps.

Manakadan (1992) has studied the ecology of waterbirds in Point Calimere

Sanctuary with special reference to impact of salt works. Anbazhagan (1996) has

attempted on the hydrobiology and benthic ecology of Kodiakkarai coastal

sanctuary. Further, a few stray notes on ecological aspects of waterbirds had

appeared in various journals (Ali 1981; Sugathan 1985; Sampath &

pg. 15

Krishnamurthy 1989; Perennou & Santharam 1990; Sampath 1991;

Balachandran & Natarajan 1992; Kazmierczak et al. 1992; Natarajan 1992;

Balachandran & Hussain 1994; Balachandran 1995; Manakadan 1995).

A lot more is needed to be done to quantify avian ecology of this swamp

and determine species-habitat relationship to base management decisions on

scientifically acceptable information to conserve avifauna of the Point Calimere

Wildlife Sanctuary and adjoining Great Vedaranyam Swamp on a long-term

basis. Further, the Great Vedaranyam Swamps are to be explored further to

know their importance with respect to the conservation of waterbirds, particularly

the migratory waterbirds.

Based on the above considerations the present study has been designed

on the Great Vedaranyam Swamp of the Point Calimere Wildlife Sanctuary,

Nagapattinam District Tamil Nadu, India during 2007–2010 with the following

objectives:

1. To document the systematic position of various ecological groups of

waterbirds in the Point Calimere Wildlife Sanctuary during October 2007-

March 2010.

2. To study the population density and diversity of waterbirds among

seasons, years and stations.

pg. 16

3. To relate the influence of physico-chemical parameters of water with the

abundance of waterbirds.

4. To investigate the influence of phytoplankton, zooplankton and

macrobenthos on the distribution of waterbirds in the study area.

5. To assess the major threats to waterbirds and suggest management

measures for the conservation of the Point Calimere Wildlife Sanctuary.