CHAPTER 1

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INTRODUCTION

1 .I The Kuttanad region

Rice 1s one of the most widely grown crops in the world and is one of

the major food cl.ops grown extensively in India. It is grown over 124

million hectares and occupies about 115''' of the tropical and subtropical

crops (Singh and Dhaliwal. 1994). It is cultivated as far north as 49" and as

far south as 35" and from sea level to the altitude of 2500 metres. After

China, lndia 1s the largest producer of rice in the world. h c e is the staple

food for about 2.4 billion people all over the world and accounts for more

than 23 percent of the total per capita daily calorie intake (Singh, 1998). In

lndia rice is grown in four major ecosystems - irrigated, rain fed low lands,

flood prone ant1 run fed uplands. No other country in the world has such a

diversit\. of rlce ecosystems. The most important rice producing states of

India are West Bengal. 4ndhra Pradesh, Bihar, Tamil Nadu, Assam and

Kerala. In Kerala, Palaghat, Trichur and Kuttanad are the main rice

producing regions

Kuttanad. popularly known as the rice bowl of Kerala, located in

central Kerala. is a large wetland habitat comprising of paddy fields,

marshes, lakes and rivers. Kuttanad consists of 54 revenue villages spread

over 10 taluks in the districts of Alleppey, Kottayam and Pathanamthitta. It

is separated frorn the Arabian sea by a narrow strip of land and is a deltaic

formation of' four river systems, namely Meenachil, Pampa, Manimala and

Achenkovil. together w ~ t h the low lylng areas (marshes) in and around the

2

Vembanad lake Most of the vast expanse in this region is lying 1 - 1.5 m

below mean sea level. water-logged throughout the year, subjected to

continued tlood submergence during monsoon and saline water ingression

during the surnmes months. The total area of Kuttanad is 1157 sq. kms, with

66048 hectares of' wetlands, 31086 hectares of garden dry lands, 18623

hectares of water wastes and the rest backwaters known as Vembanad lake

(Aravindakshan and Joseph, 1990). Vembanad lake is the largest backwater

body in tierala sltuated between latitude 9"28' and 1O010' north and

longitude 76'1.3' arid 76'3'1' east (Kurup et al,, 1990) with overlapping

estuarine, brackish water and fresh water habitats beginning at Cochin where

it merges with Arabian sea. The Vembanad lake extends southwards parallel

to the coastal line, as far as Alleppey and stretches over the revenue districts

of Ernakulam. Kottayam and Alleppey. The lake is divided by a man made,

1402 m long barrage, the Thanneermukkom bund extending across the lake,

and the water flow through the bund is regulated by shutters (Fig. 1).

The vast area of paddy fields in Kuttanad extends fiom 9'17' N to

9'40' N and 7 6 19' E to 76'33' E (Aravindakshan and Joseph, 1990). Among the

wetland 53639 hectares have 'been identified as puncha rice fields, most of which

are at or below sea level (KWBS, 1989). These are divided into

"padasekhararns." literally meaning groups or blocks of paddy fields and are

separated by canals, bunds and water-logged land masses. The puncha lands of

Kuttanad are classified under three categories based on elevation, geographical

formation and soil characteristics, into Karappadon~s, Kayal lands and Kan lands.

0 15*m - - - K u i l o n o d b o u n d a r y

**.....** B a u n d o r r e r o l a g r o n o m i c l o n e r

Figure 1 Map of Kuttanad area

The Karappadoms are generally situated along with the waterways and

constitute the lower reaches of the eastern and southern periphery of

Kuttanad, usually 1-2 m below mean sea level. Kayal lands are reclaimed

beds of Vembanad lake for agricultural purpose and the elevation ranges from

1.5 to 2.5 m below the mean sea level. R - Block is such a reclaimed island

with surrounding granite retention walls. Rani, Chithira and Marthandom ase

reclaimed paddy fields. The Kari lands situated in Ambalappuzha, and

Vaikom taluks is peaty and marshy in nature and are overgrown in many

areas with wild weeds and grass and most of the Kari lands lie at or below

mean sea level

'Puncha' is the main paddy crop in Kuttanad sown in November or

December and harvested by the end of March. The 'virippu' is the additional

crop grown from May to the end of June and harvested in September or

October. High yielding varieties of rice are sown in all the areas of Kuttanad.

The main pests of paddy are stem borer, gall midge, leaf folder, brown

plant hopper, thrips and rats (Nair et al., 1990). The peak incidence of gall

midge is dur~ng the month of October/November and that of brown plant

hopper during Februarylblarch Another peak of brown plant hopper is in

AugustiSeptember after the main floods .The most frequently encountered

diseases affecting rice in Kuttanad are sheath blight, sheath rot, bacterial leaf

blight and blast. Blast tends to affect the puncha crop whle sheath blight and

sheath rot affect all crops and bacterial leaf blight affects only virippu crop

(Zacharia e/ 01.; 1990). Rainfall, temperature, light, carbon dioxide

concentrat~on, relative humidity and wind velocity influence the yield directly

by affecting the development and grain formation or indirectly by affecting

the incidence of pests and diseases (Sharma and Singh, 1999). Insecticides

disrupt the natural enemy complex in rice fields and the cultivation of high

yielding vanehes creates a great change in paddy agroecosystem (Kiritani, 1979).

The malor weeds encountered are wild rice (Oiyza mjpogon),

Echinuchlou sp. and various aquatic weeds that swept into paddy fields

(Sasidharan c/ a/., 1990). Of these, wild rice and Echinochloa sp. are the

major problems and have to be removed manually or with herbicides. High

yielding paddy varieties require heavy doses of fertilizers and pesticides.

The farmers in Kuttanad apply adequate doses of fertilizers and sometimes

the applications are found to be higher than the recommended measure.

The quantity of pesticides used is also high, somewhat hlgher in puncha

season than in virippu season and thus the treatments often cause severe

ecological damage. Darnage of natural bio control agents often permits

secondary outbreak of other specles that were formerly not pests. Many

insects have developed resistance to pesticides

The soil of Kuttanad is silty clay and is extremely acidic in reaction

(Liji and Thomas, 1990). The acidity is due to the production of sulphuric

acid by microb~ological oxidation of sulphur compound present in the soil.

Toxic proportions of iron, aluminum, manganese and sulphides are present in

the soil. Soil acldity is a major constraint which retards the production of rice

in the wetland rice soils of the tropics, which has got aggravated in recent

times with the introduction of high yielding varieties of rice and intensive use

of fertilizers. In Kerala. it is estimated that there are five lakh hectares of rice

lands and the rnajor part of them is acidic in reaction (Usha and Varghese,

1997). Toxicity become severe on the top soil by the processes of deleterious

salts corning to the surface by capillary action when the fields are dry during

summer months or when the water outside the field rises high. The soils of

backwaters (Kayal lands) which are reclaimed beds of Vembanad lake are

more seriouslq affected by salinity. The fields lying in the banks of rivers and

waterways are less affected as they are periodically enriched by slit brought

down by the rivers during the floods.

The developmental activities in Kuttanad viz., the Thottappally spill

way, the salt water barrier at Thanneennukkom and the improvements of

padasekharam bunds under Kerala Tourism Development Corporation

(KTDC) scheme had wide long effects on rice cultivation and Kuttanad

ecosystem. Since the construction of the Thanneermukkom barrier, the part of

Cochin backwaters has been transferred into an area where the salinity is too

low for the prawn and fish to grow. Moreover, the migration routes of marine

fish and prawns are interrupted by the barrier, its gates being closed during

the pre monsoon period when maximum upstream migration takes place

(Padmakumar 1.t (11.. 2002). The area south of the barrier is best as a nursery

ground for post larval prawns which need salinity of about 15-20 ppt for

optimal growth. During the closure of the banier in the dry season, the

upstream area IS rio longer flushed by the tides and water is polluted by

pesticides from agricultural lands and organic wastes dumped into the

Kuttanad waters. Due to the elimination of the risks from natural hazards, the

discipline in the season of rice cultivation has gone and the non judicious

fertilizer application and plant protection measures increased the incidence of

pests and diseases and consequent crop loss has become quite common.

Intensive cultivation has led to poor soil health and water quality resulting in

yield decline even with higher inputs. The production of rice in Kerala meets

only 42 pel- cent of the states requirements. The area under the crop had

declined by 17 - 47 percent in the state during the period of 1975 - 1976 to

I 984 - 1985 About 80 percent of the area is under high yielding varieties in

Icottayarn district (Kerayalar and Elsarnma, 1993). The gap between demand

and local production of rice in Kerala is widening primarily because of the

continuous pace at which ri~:e areas are giving way to urbanisation.

1.2 Need for the conservation of wetlands

Wetlands have been described as a half way world between terrestrial

and aquatic ecosystems (Smith, 1990). They are fragile ecosystems since all

of their troph~c levels contain organisms that are sensitive to changes made.

Wetlands prov~de a major role in the landscape by providing unique habitats

for a wide varlety of flora and fauna (Bambaradeniya et al., 1998) and are

essential for barious hydrological and ecological processing. Unfortunately

wetlands are fast d~sappearing all over the world, and the time has come to

make a coordinated effbrt to halt this trend and to optimise the use of

wetlands. The third meetlng of the conference of the contracting parties of the

Ramsar- Convention in June 1987 defined the wise use of wetlands as their

sustainable utilisation for the benefit of human kind in a way compatible with

the maintenance of'the natural properties of the ecosystem. Marshes are fringe

habitats and are amphibious environments characterised by shallow water

with predominantly emergent vegetation (Welty, 1982). They are highly

productive ecosystems enclosing a complex food web. Most of the shallow

lakes and marshes have been filled up and the characteristic wetland

vegetation has disappeared together with the dependent fauna. The most

serious impacts on Kuttanad wetlands are made indirectly through the

8

construction o f the Thottappally spillway, Thanneennukkom barrier etc. in

Kuttanad. which caused changes in the hydrological regimes of Kuttanad.

Intensive and extensive cultivation of high yielding varieties coupled with the

application of geometrically increasing amounts of agrochemicals has resulted

in the deterloration in environmental quality and aggravates the pest problems

(Arora and Dhaliwal. 1996).

Rice paddies are one of the wetland types recognized by the Ramsar

convention 'These are anthopogenlc wetlands managed for rice cultivation

and experience both dry and wet conditions depending on water availability.

According to Subramanya and Veeresh (1998) rice fields are not mere

monoculture habitats but are in effect dynamic and heterogeneous man made

habitats created by varying microhabitat conditions and their succession.

1.3 Agricultural ornithology

Agricultural orn~thology aims at obtaining scientific information of

birds in relation to agriculture and using this information for their

management. Avifauna in agricultural landscape includes all kinds of birds

namely granivores, fmgivores, insectivores, carnivores, nectarivores,

piscivores and ornnlvores. The dual role played by buds in agnculture is very

well known (Ali, 1949). Most blrd species play a useful role in agnculture by

having a potent check on insect and rodent pests, where as some granivorous

bird species ~nflict economic losses to crops and stored grains. Bird

management involves conservation of useful species and control of pests. We

need to keep all existing avian species in balanced numbers in the cultivated

landscapes so as to have a sustained agricultural production. It is interesting to

note that only 75 percent of the 1200 species of birds found in India have

been reported to inflict damage to fruits and crops (Dhindsa and Saini, 1994).

All avian species are not surviving equally healthy in the agroecosystem.

Habitat destruction and food chain poisoning by indiscriminate use of

pesticides have resulted in the decline of many insectivorous and predatory

bird species to a dangerously low population level. This has created an

ecological crisis in the avian communities of agricultural landscapes

(Dhindsa, 1984).

According to Connor and Shrubb (1986) rice fields provide

concentrated and highly predictable source of food to many birds and several

migratory birds use rlce ecosystem as stop over or transit areas because of

easy food availability. According to Borad et al. (2000), foraging activity of

birds in harvesting rice fields help in reducing the inoculum load of insect

pests and weeds by selecti\~ely feeding on them. We need to study in detail

the populatron dynamics of birds in wetlands because birds from marshy

habitats could easily adopt themselves to rice habitat conditions.

Om~thology, particularly agricultural ornithology has been and is still

in a low prrorib research area in India. Detailed information on population

dynamics of birds in agricultural ecosystems is not available. Management

questions can be answei-ed only if we have sound knowledge of various

ecological aspects of that ec;osystem. Studies are required on the ecology and

conservation of' many useful birds whose population is declining in cultivated

areas. Studies on bird specicrs diversity in relation to rice field characteristics

are very few However, studies are available describing the pestiferous or

beneficial role of birds in paddy agroecosystem in India, even though such

studies are rare in Kerala

The main study slte selected for the present study is located at Pallom

in Kottayam d~stnct, wh~ch comes almost at the middle of the belt of paddy

fields surrounding Vembanad lake from Kumarakom to Kainady in Alleppey.

The Vernbanad wetland system is a heaven for ornithologists because of its

rich avifauna. The bird :sanctuary situated on the tourist complex at

Kumarakom, and Pathiramanal, a charming island situated in the middle of

Vembanad lake. shelter different types of resident and migratory bird species.

The paddy fields adjacent to Vembanad lake form the main feeding ground

for many of these birds. These fields during inundated fallow conditions

harbour different types of fishes that swept in from the lake and thus provide

niche for different types of birds durlng different field conditions.

No authentic detailed scient~fic ~nformation is available describing the

population fluctuation of birds in rice fields according to various cultivation

practices and habitat characteristics. Hence the present study was undertaken

with a view to understand the various features of paddy agroecosystem and its

bird fauna. thereby to stress the need for the conservation of wetland

ecosystems

1.4 Major objectives

Birds constitute an rmportant component of paddy agroecosystem.

Despite being one of the major man made habitats, its avifaunal pattern is

poorly understood Only a very few studies on the structure of bird

community dependmg on the crop have been carried out in India (Toor et al.,

1986; I'arashalya c/ a/. 1996: Shyama, 1997; Subramanya and Veeresh,

1998). No integrated study on different aspects of avifaur~al pattern in rice

field ecosysterri has been undertaken in Kerala. Hence the:& focus sf the , . ,;" . i 0 ;I ;- ./ .: ~-:,

study is to understand and relate paddy field ecosystem with the-biid h a

and to emphas~ze the need for the conservation of paddy agroecosystem and

to help plan a Inore meaningful lice field management strategy with the

following rnaln object~vec

1.4.1 Water quality and plankton

1. To study the various physicochemical properties of water in rice fields

during cult~vation and inundated fallow conditions.

2. To understand the varlous planktonic groups and their percentage

occurrence in relat~on to certaln physicochemical factors of water.

1.4.2 Soil characteristics

1 . To get a basic idea about the various physicochemical properties of soil

existing in the varlous study areas.

1.4.3 Vegetation

1. To prepare a l ~ s t of the flora [macrophytes and weeds] of the study

areas

1.4.4 Arthropod pests and predators

1 To deter-m~ne the percentage occurrence of arthropod pests and

predators durlng varlous stages of the growth of paddy.

1.4.5 Fish fauna

1. To prepare a 11st of fish fauna present during inundated fallow

cond~tions

1.4.6 Amphibians, Reptiles, Mammals

I To p ~ e p n ~ e a hst of amph~b~ans, reptlles and mammals occurring in nce

field\

1.4.7 Avifauna

1. To critically evaluate the population of buds during various growth

stages of paddy.

2. To correlate the bird population with the various climatic factors.

3. To study the habitat preference of birds.

4. To compare the bird species composition in the marsh field and the

paddy field.

5 . To analyse the changes in h ~ r d population associated with the field

convers~on activit~es done in marsh field.

6. To study the bird species composition in the study areas according to

the food preference

7. To estimate the diversity index of bird species in the various study

areas.

8 To evaluate the fluctuation m the population of migratory birds in the

study aren

9 To compare the bird population fluctuation in the different seasons of

paddy cult~vatlon