eChapters

Introduction

Soil, a dynamic living matrix, is an essential part of the terrestrial ecosystem. It is a critical resource not only to agricultural production and food security but also to the maintenance of most life processes. Soils contain enormous numbers of diverse living organisms assembled in complex and varied communities ranging from the myriad of invisible microbes, bacteria and fungi to the more familiar macro-fauna such as earthworms and termites. The diversity in soils is several times higher than that above ground. Each hectare top soil contains approximately 1,000 kg of different fungi, 500 kg of bacteria, 750 kg actinomycetes and 150 kg of algae and many protozoa (Table 1). These diverse micro-organisms interact with one another and with the plants and animals in the ecosystem forming a complex system of biological activity. Environmental factors, such as temperature, moisture and acidity, as well as anthropogenic actions, in particular, agricultural practices affect soil biological communities and their functions to different extents. Diversity of soil micro-organisms has emerged in the past decade as a key area of concern for sustainable soil health and crop production. Besides, the well-being and prosperity of earth’s ecological balance, the sustainability of agricultural production systems directly depends on the extent and status of microbial diversity of soil.

Introduction

Drought is the most important abiotic factor that adversely affect growth and crop production. Drought stress can altered the normal physiological processes that influence one or a combination of biological factors for yield and yield attributing traits (Ashraf, 2010). The abnormal metabolism due to stress may reduce plant growth (Claves et al., 2002). Production is limited by environmental stresses, according to different scholar estimates, only 10 per cent of the world’s arable land is free from stress, in general, a major factor in the difference between yield and potential performance, environmental stresses. Drought is one of the most common environmental stresses that almost 25 per cent of agricultural lands for agricultural farm products in the world are limited (Loresto, 1976; Chaves, 2002). Drought occurrence in India is also very frequent. Drought occurred in past 1967, 1968, 1969, 1972, 1974, 1979, 1987, 2002, 2009 and had considerable impact on food grain production. For example, the drought of 1966-67 reduced overall food grains production by 19%. The drought of 1972-73 reduced the food grains production from 108.95 million tonnes to 95 million tonnes, causing a loss of about $ 400 million $. The 1987 drought in India damaged 58.6 million ha of cropped area affecting 285 million people (Ray et al., 2015). Drought in 2002 has reduced food grains production to 174 million tonnes from 212 million tonnes resulting in decline of 3.2% GDP (Rathore et al., 2009; Ray et al., 2015).

The water deficit reduces crop yield due to decrease in photosynthetic area, decreased radiation use efficiency and harvest index (Earl and Davis, 2003). Drought stress affect the water balance and plant metabolisms. Plants under drought conditions use various changes to tolerate stress conditions and increase drought tolerance which includes changes in whole plant, tissue, at physiological and molecular levels. Appearance of a single or a combination of inherent changes determines the ability of the plant to stand under aridity conditions. Tolerant plant adjusts its water balance by osmotic adjustment, deep root systems and by transient leaf rolling.

Introduction

Soils are formed by weathering of rocks and minerals and all soils contain some amount of soluble salts. Many of these act as a source of essential nutrients for the healthy growth of plants. However, when quantity and quality of salts in the soil near rhizosphere exceeds a particular value, growth, yield and/or quality of most crops is adversely affected. Such a soil is called salt-affected. The degree of adverse effects depends upon the type and quantity of salts, crop and its variety, stage of growth, cultural practices and environmental factors viz. temperature, relative humidity, and rainfall etc. Development of salinity and waterlogging is a serious problem in arid and semi-arid regions of the world and threatening the sustainability of irrigated agriculture.

Salt-affected soils occupy an estimated 952.2 million ha of land in the world that constitutes nearly 7% of the total land area and nearly 33% of the potential arable land (Dudal and Purnell, 1986). In India, the salt affected soils account for 6.727 million ha i.e. 2.1% of geographical area of the country. These soils are mostly found in the states of Uttar Pradesh, Haryana, Punjab, Madhya Pradesh, Bihar and Andhra Pradesh. In the last 25 years 1.1 million ha of alkali soils have been reclaimed in the states of Haryana, Punjab and Uttar Pradesh. These have contributed to the additional food grain production of 10 million tonnes annually. Reclamation of alkali soils have also decreased the incidents of floods and malaria and increased the groundwater recharge.

Introduction

The Indian Himalayan Region (IHR), with geographical coverage of over 5.3 lakh km², constitutes a large proportion of the hotspot and, therefore, contributes greatly to richness and representativeness of its biodiversity components at all levels. Out of this 5.3 lakh km², 33.13 million ha area is being constituted by the North-Western Himalayas.^. Further, most of the water used to grow maize crop in the sub-humid foothill region of northwest Himalayas, is derived from rainfall. Erratic rains, fragile ecosystems and traditional indigenous management practices are mainly responsible for the current situation (Kukal and Bhatt, 2010). IHR covers 11 states entirely (i.e. Jammu & Kashmir, Himachal Pradesh, Punjab, Uttarakhand, Sikkim, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya), and two states partially (i.e. hilly districts of Assam and West Bengal). The region represents nearly 3.8% of total human population of the country and exhibits diversity of ethnic groups which inhabit remote terrains. Further it is reported that the Northwestern Himalayan region (NWHR) which spreads to an approximate area of 33.13 million ha, comprising of Jammu & Kashmir, Himachal Pradesh, Uttarakhand is 10.1% of country’s total geographical area, supports 2.4% and 4% of human and cattle population of the country, respectively. This region has a diverse climate, topography, vegetation, ecology and land use pattern. The annual average rainfall varies from 80 mm in Ladakh to over 200 cm in some parts of Himachal Pradesh and Uttarakhand. The major natural resources are water, forests, floral, and faunal biodiversity. Forests constitute the major share in the land use of the region with only 15% of the net sown area and 162% cropping intensity (Bhatt, 2011).

Introduction

Farm mechanization is application of machine power to work on land, usually performed by animate and mechanical power. It is also defined as an economic application of engineering technology to increase the labour efficiency and productivity. However, it not only includes production, distribution and utilization of a variety of tools, machinery and equipment but also planting, harvesting and primary process. Mechanization has a major impact on demand and supply of farm labour, agricultural profitability and a change in rural dynamics.

Introduction

Worldwide, salt–affected areas are estimated to range from 340 million ha to 1.2 billion ha (FAO, 2007; Oo et al., 2015; Ahmad et al., 2016; Drake et al., 2016). Millions of hectare of these salt affected soils are suitable for agricultural production but are unexploited because of salinity/sodicity and other soil and water related problems (Abrol et al., 1988). Salt-affected soils are reported to comprise 42.3% of the land area of Australia, 21.0% of Asia, 7.6% of South America, 4.6% of Europe, 3.5% of Africa, 0.9% of North America and 0.7% of Central America (El-Mowellhey, 1998). In India, out of 329 million ha geographical land area of the country about 175 million ha suffers from different problems and is getting further degraded through natural or man-made processes. Majority of these lands is treated as wastelands as their productivity is low due to soil based constraints like water logging, salinity and sodicity. According to FAO, salinization of arable land will result in 30% to 50% land loss by the year 2050 if, remedial actions are not taken. Recent estimates indicate that 6.73 million ha (NRSA and Associates, 1996) land is suffering from salinity and sodicity problems in India. High salt deposits inherited by the soil from the original parent material during soil forming processes and poor drainage are important factors contributing to the development of such soils. These lands occur in different biogeographic zones and therefore consist of diverse morphological, physical, chemical and biological properties. These soils are universally low in fertility and due to the adverse edaphic environment; they are devoid of any vegetation because of excessive exchangeable Na+ associated with high pH (>8.5) which impairs the physical condition of the soils and adversely affects water and air movement, nutritional and hydrological properties of the soils (Suarez et al., 1984; Gupta and Abrol, 1990; Sumner, 1993; Garg, 1998).These lands are largely carbon-depleted but can be brought back to their native carbon-carrying capacity by reforestation through agroforestry systems. The presence of CaCO3 concretions at various depths (caliche bed) causes physical impedance for root proliferation, therefore, making it difficult for tree establishment and restrict the choice of arable crops to be grown (Shukla et al., 2011; Singh et al., 2012a).

Introduction

Livestock is an important component of Indian agriculture contributing 28% of agricultural gross value added (GVA) of the country. Agriculture, as such, contributes 16.4% of country's GVA (Economic survey, 2017-18). Livestock as a source of income has seen a steady increase from 4% to 13% in a decade time (2002-2012). India, with 2.29% of the world land area, is maintaining about 10.71% of the world’s livestock population. The milk production in the country increased from 17 million tonnes in 1950-51 to 187.7 million tonnes in 2018-19. The feed and fodder play an essential role in the health and productivity of livestock. Even though India is the world largest milk producer with 21% of global production, the productivity (1700 kg/year) is far below the world average (2574 kg/year) (FAO STAT, 2018). One of the main responsible factors (50.2%) for this low productivity is the deficiency in feed and fodder. Although forage crops are the critical component of livestock-based farming system, the area under cultivated fodder is static to around 8.4 million ha (5.23%) since last two decades due to the competition of land use with other crops. Availability of the fodder determines the productivity and profitability of the livestock rearing because fodder and feeds constitute about 60% of the total cost of milk production, which can be lowered by enhancing the green fodder-based feeding system. The traditional grazing lands are gradually diminishing because of urbanization, expansion of the cultivable area, grazing pressure, industrialization etc. These factors coupled with stagnation of area under cultivated fodder resulted in a severe shortage of feed and fodder to the extent of 26% in dry crop residues, 35.6% in green fodder and 41% of concentrates (IGFRI, 2011). This gap in demand and supply may further rise due to consistent growth of livestock population at the rate of 1.23% in the coming years. The share of the in-milk population to total population has increased from 23% to 27% in the case of cattle and from 33.64 to 34.74% in buffaloes from 2012 to 2019. The year-on-year growth rate of milk is approximate 6%. Thus, to sustain this growth rate and for further expansion to meet the demands of the ever growing human population, livestock needs a sustainable supply of feed material. To reduce the demand and supply gap, the production and productivity of fodder crops need to be enhanced. The productivity of cultivated fodder crops is low, due to the least attention and allocation of minimal production resources and lack of dissemination of the production techniques to stakeholders involved in the forage resource development. The present chapter highlights the recent advances in the forage crop production technologies. The comprehensive compilation of information at one place provides the opportunity to get the holistic picture of forage production altogether.

Introduction

The various kinds of plants present on earth have been used over the millennia for human welfare in the promotion of health and as drugs and fragrance materials. About 80% of the world’s inhabitants rely mainly on herbal medicines for their primary health care, while medicinal plants continue to play an important role in the health care systems of the remaining 20%. The use of herbal medicine and medicinal plants in most developing countries, as a normative basis for the maintenance of good health, has been widely observed (UNESCO, 1996). According to WHO (1998), herbal medicines are finished, labelled medicinal products that contain as active ingredients, above ground or underground parts of plants or other plant materials, or combinations thereof, whether in the crude state or as plant preparations. The plant materials referred to above include juices, gums, resins, fatty oils, essential oils and any other substances of this nature. Herbal medicines may contain excipients in addition to the active ingredients (WHO, 1991). Remarkably, even today there is no real definition for this special group of plants that has been accompanying mankind throughout history. Most frequently, medicinal plants are defined as feral and/or cultivated plants that, based on tradition and literature records, can be directly or indirectly used for medical purposes. The basis of medicinal use is that these plants contain so called active ingredients (active principles or biologically active principles) that affect physiological (metabolic) processes of living organisms, including human beings.

The conception about aromatic plants is even less definite. The term aromatic indicates plants having an aroma; being fragrant or sweet-smelling, while the word aroma is supposed to imply also the taste of the material (aromatic herbs). Since, large number of plants possess both medicinal and aroma properties which leads to complexity and overlapping uses of active ingredients, making impossible to establish rigid categories or a practical classification for medicinal and aromatic plants. For example; Anise, dill, coriander, thyme, etc. are equally known as medicinal, spice and essential oil crops. Thus, frequently these plants are simply referred to as medicinal plants, disregarding their specific features. More recently, the term “Medicinal and Aromatic Plants” (MAPs) has been used in a slightly broader sense, distinguishing the fragrant (aromatic, ethereal) ingredients containing group of medicinal plants.

Introduction

The general recommendation for intake of fruits and vegetables is at least 400 g/ person as recommended by World Health Organization (WHO), which amounts to five servings of 80 g/day or about 146 g/person/annum. For vegetables, the recommended intake requirement is at least 300 g per day per individual. This 300 g requirement must include 50 g leafy vegetables, 50 g roots and tubers and 200 g other vegetables (Kapur, 2016). Current annual vegetable production including potato, based on recent three years (2015-16, 2016-17, 2017-18) average is around 177 million tonnes from 10 million ha giving a productivity of 17.7 tonnes/ha. With this average and stagnating production and assuming Indian population at 133 crores (1.33 billion) and 25% post-harvest losses, per capita per day availability of vegetables comes to 273 g leaving a gap of 27 g between the recommended dose and the availability of vegetables/head/day in India. By 2050, the projected population of India is 1.5 billion and to meet the requirement of this population, vegetable production will have be 220 million tonnes, of course making allowance of 25% post-harvest losses. Considering all kind of constraints on the available land area of vegetables, the vegetable area will be around 10 million ha and consequently, major gain of production will have to come from productivity increase from current level of about 18 to 22 tonnes/ha and this seems to be a gigantic task as during last several years, the productivity of vegetables in India has been between 17 and 18 tonnes/ha, an indication that perhaps productivity has reached to a plateau. This situation will call fall massive interventions on technological fronts in terms of innovative products with focus on better hybrids with higher yields, and resistance to biotic and abiotic stresses coupled with horizontal scaling up of modern production technologies. This chapter looks into the modern production technologies as applicable to vegetable crops in India to boost the productivity further from current 18 tonnes/ha to at least 22 tonnes/ha.

Introduction

Sugarcane is a vital commercial crop of our country that occupies around 5.11 million ha of land with an annual cane production of around 400.16 million tonnes and yield of 78.25 t/ha. Sugarcane occupies 2.67% of the cultivated land area and about 7.5% to the agricultural production in the country (DAC, 2020). This crop is a source of earning and livelihood for about 35 million farmers and approximately equal number of labourers. After textile industry, the sugar industry holds its place for the largest agro-based industry in country. Around 40-50% of the cane is utilised in 435 sugar industries present in India for the manufacture of about 15 million tonnes of sugar.

This crop is also a source of raw material for two important small scale industries, i.e., gur and khandsari. These industries utilises about 50-55% of the sugarcane produced for production of about 10 million tonnes of these products altogether. Besides, sugarcane crop is also the producer of molasses, chief by product, which is the main source for production of alcohol. In the year 2018-19, about 13.79 million tonnes of molasses is produced by our country. Apart from this, the left over fibrous material of sugarcane termed as sugarcane bagasse is also a source of production of electricity in the sugar mills. The left over extra bagasse is now-a-days utilised for even production of paper in paper industries. Also, co-generation of power by this product of sugarcane as fuel is considered to be best practical thing in most of the sugar mills. Using this as a raw material, about 3500 MW power may be generated each year without the use of any extra fuel and money being less than normally utilised in case of fuel production from thermal powers. Press mud is also one of the by-products obtained from sugarcane which is considered to be rich source of organic matter and micro and macro nutrients. Even the green tops of sugarcane are being used as cattle fodder. Besides, the cool sugarcane juice full of energy is in great demands in urban area to quench the thirst of people, especially in hot summer seasons (Anonymous, 2008). The trend of sugarcane production over the years is given

Introduction

Oilseeds are the third most important group of crops after cereals and pulses in India. These are important food crops which also find their place in industrial use. Oilseeds have been an integral component of Indian agriculture since time immemorial. On the oilseeds map of the world, India occupies a prominent position, both in terms of acreage and production. India is the 4^th largest edible oil economy in the world and contributes about 10% of the world oilseeds production, 6-7% of the global production of vegetable oil, and nearly 7% of protein meal. The oilseeds production statistics of the world for the year 2016-17 includes a production of 549.98 million tonnes from an area of 234.57 million ha with the productivity of 2.34 tonnes/ha. The top countries include U.S.A., China and India with U.S.A. ranking first in all area, production and productivity of 39.25 million ha, 126.94 million tonnes and 3.23 tonnes/ha, respectively. Next is China which ranks 2^nd in production and productivity but 3^rd in terms of area; the area, production and productivity being 22.72 million ha, 54.92 million tonnes and 2.42 tonnes/ha, respectively. India ranks 2^nd in terms of area, i.e. 33.83 million ha but 3^rd in both production and productivity being 36.32 million metric tonnes and 1.07 tonnes/ha respectively.

Introduction

Pulses are the second most important group of crops after cereals in India. They are important food crops for nutritional security, soil health and sustainable agriculture. Consequently, they remained an internal component of Indian agriculture especially under rainfed since time immemorial. They are among the ancient food crops with evidence of their cultivation for over 8,000 years. India, China, Brazil, Canada, Myanmar and Australia are the major pulse producing countries with relative share of 25%, 10%, 5%, 5% and 4%, respectively. In 2017, the global pulses production was 95.98 million tonnes from an area of 95.17 million ha with an average yield of 1008 kg/ha. Dry beans contributed 32.7% to global total pulses production followed by chickpea (15.4%), dry peas (16.89%), lentil (7.91%) and pigeonpea (7.1%). About 70% of the global pigeonpea, 60% of chickpea and 17% of lentil area falls in India (FAO STAT, 2018). India is the largest producer and consumer of pulses in the world contributing around 25-28% of the total global production.

India can be proud of growing the largest number of pulse crops (grain legumes) in the world. Over a dozen pulse crops including chickpea (Cicer arietinum), pigeonpea (Cajanus cajan), mungbean (Vigna radiata), urdbean (Vigna mungo), cowpea (V. unguiculata), lentil (Lens culinaris), lathyrus (Lathyrus sativus L.), frenchbean (Phaseolus vulgaris), horsegram (Macrotyloma uniflorum), field pea (Pisum sativum), moth bean (V. aconitifolium), etc. are grown in one or the other part of the country throughout year. The latest data (2017-18) indicate that the present production of pulses is 25.23 million tonnes from an area of 29.99 million ha with productivity of 841 kg/ha (DAC, 2019) (Fig. 1). The stagnant growth of pulse production and continuous increasing human population in the country led to decline in per capita consumption of pulses from 67 g/day/person during 1951 to 35 g/day/person during 2010 (Indian Council of Medical Research recommends 65 g/day/person).

The most important pulse crops grown are chickpea (48%), pigeonpea (15%), mungbean (7%), urdbean (7%), lentil (5%) and field pea (5%). To fulfill domestic demand of pulses in the country, India has to import 3-4 million tones of pulses every year. In order to ensure self-sufficiency, the pulse requirement in the country is projected to be about 50 million tonnes by 2050 which necessitates an annual growth rate of 4.0% (IIPR, 2013).

Introduction

Pearl millet (Pennisetum glaucum L.) is the most widely grown type of millet and it is an important staple food grain crop for millions of people in arid and semi arid regions of the world. Pearl millet is very well adapted crop to growing areas characterized by drought, low soil fertility, and high temperature. It is also performs well in soils with high salinity or low pH. Because of its tolerance to difficult growing conditions, it can be grown in areas where other cereal crops, such as wheat or maize, would not survive. Physiologically, it is a C₄ plant which imparts it potential to grow under hot and dry climatic conditions. Among cereals, it is highly responsive to fertilizers and has highest water use efficiency. Pearl millet is being grown as dual purpose crop for both grain and fodder in dry areas like Rajasthan where animal production is complimentary with crop production. Pearl millet is also a good source of important essential minerals for human health like Fe and Zn hence it is useful to alleviating malnutrition.

Introduction

Maize (Zea mays L.) is one of the most versatile promising crops having wider adaptability under diverse agro-climatic conditions. Worldwide, maize is known as “Queen of cereals” because it has the maximum genetic yield potential amongst the cereals. It is cultivated on nearly 197 million ha in about 170 countries having wider diversity of climate, soil, biodiversity and management practices that contributes 36% (1135 million tonnes) of the global grain production. The United States of America (U.S.A.) is the largest producer of maize contributes nearly 33% of the total production in the world and other important growing countries are China, Brazil, India, Argentina, Indonesia, Ukraine and Mexico (Table 1).

Introduction

Wheat is pre-eminent both in regard to its antiquity and its importance as a food of mankind in the world. In prehistoric times, it was cultivated throughout Europe and was one of the most valuable cereals of ancient Persia, Greece and Egypt. Wheat has been cultivated for several thousand years in India with the evidence of presence of wheat grains in the Mohen-Jo-Daro excavations. Till 1947, the total wheat production was only about 6 million tonnes and was not sufficient to meet the demand, leading to large scale importation of wheat. Subsequently production increased due to an increase in both total cropped and irrigated area. Wheat crop has exhibited a robust growth trend since the onset of the ‘green revolution’ in 1968. India, one of the greatest success stories of ‘green revolution’, is the second largest producer of wheat in the world after China. During 2018-19 (Fig. 1) India produced a record breaking 101.20 million tonnes of wheat from 29.62 million ha area indicating 3.42 tonnes/ha wheat yield (ICAR-IIWBR, 2019). On the other hand, India is also the second largest wheat consumer after China. Thus, wheat and its various products play an increasingly important role in managing India’s food security and India became the wheat surplus nation as against the wheat deficient nation during 1960’s. The tremendous progress in area, production and productivity of wheat to the tune of 2.9, 12.2 and 4.2 times, respectively as compared to 1950 has made India (Table 1) the member of elite group of wheat exporting countries (Workman, 2018).

Introduction

Rice is the staple food for over half the world’s population. China and India alone account for ~50% of the rice grown and consumed. Rice provides up to 50% of the dietary caloric supply for millions living in poverty in Asia and is, therefore, critical for food security. Globally, share of Asia continent in rice production is more than 90% followed by America (5.2%), Africa (3.4%) and Europe (0.6%). It is becoming an important food staple in both Latin America and Africa. Record increases in rice production have been observed since the start of the ‘Green Revolution’. However, rice remains one of the most protected food commodities in world trade. Rice is a poor source of vitamins and minerals, and losses occur during the milling process. Populations that subsist on rice are at high risk of vitamin and mineral deficiency.

The Indian population of 1.32 billion is projected to reach 1.53 billion by 2030 A.D. Goyal and Singh (2002) estimated a demand of 146 million tonnes of rice (taken as 50% of total cereals) by the year 2030. On the other end of the scale, 3^rd projection puts rice demand to be 156 million tonnes by 2030 (ICAR, 2010). To meet this, it is immensely necessary to increase the productivity levels without adversely affecting the natural resource base. Achievement of the targeted production would be an uphill task in the coming decades with the shrinking natural resource base, deteriorating soil health and soil productivity, declining input use efficiency, plateauing of yields in irrigated ecologies and lack of a major yield breakthrough in rainfed ecologies. Further, slowdown in the growth rate of cereal production and growing population pressure have emerged as formidable challenges for the future food and nutritional security in India. These challenges will be more extreme under emerging situations of natural resource degradation, high energy demands, volatile markets and risks associated with global climate change (Jat et al., 2016; Lal, 2016). Since, rice is the staple food for our country’s food security primarily depends on this wonderful crop. Globally rice is cultivated now in 167 million ha with annual production of around 769 million tonnes (499.3 million tonnes, milled rice) of rough rice and average productivity of 4.6 tonnes/ha (3.62 t/ha, milled rice) of rough rice (FAO STAT, 2017). In Asian countries, >90% of the rice is produced and consumed. The other continents in which rice is grown are Africa (7.78% of the global area), South America (6.4%) and North America (1.4%).

Tropical forest bird community

Species richness at Silent Valley and Mukkali were similar. Most of the birds at Silent Valley were sighted with in a distance of 4m during the census. At Mukkali this distance was up to 9m. Yellowbrowed Bulbul was the most common and dominant species found at Silent Valley. Most common species found at Mukkali was Black Drongo and dominant species was Jungle Babbler. A total of hundred and thirty-seven species of birds were recorded from the study area. There is no significant difference in bird species richness between years during monsoon and summer seasons at Silent Valley. But a significant difference in species richness is obtained between years in both seasons, at Mukkali.

Four endemic and threatened species of birds were recorded from the study area. This shows the conservation value of the study area. Total number of birds sighted in each month showed significant difference at Silent Valley and Mukkali. This is due to the movement of birds influenced by the climatic and other parameters. Overall density of birds was high at Silent Valley (1122 birds/km²) and low at Mukkali (780 birds/km² ). This indicates the ability of tropical evergreen forest to harbour more birds than tropical moist deciduous forest. The number of individuals/km² recorded is comparable to other tropical forests in the world and from this observation we can also conclude that the study area is supporting a rich bird community.

Wetland birds serve an important ecosystem function of accelerating the nutrient cycling in the feeding grounds (Morales and Pacheco, 1986) and regulating fish populations (Miranda, 1995). According to Drent and Dann (1980), the availability of food is of primary importance to the birds during migration when, they store energy for winter survival and successful completion of migration. Many migrant shorebirds relay on a few key stopover sites to complete their annual migratory cycle (Myers et al., 1987), which provide a unique combination of food resources and habitat necessary to support these large numbers of birds (Myers, 1984).

When animal species assemble at a particular area, they utilise individual but overlapping segments of the habitat (MacArthur, 1958). Karr (1980) stated that resource utilization pattern and the community organization are determined by a combination of variables. The availability and preference of the food organisms, feeding behaviour and utilization of the habitat for feeding and reproduction differ in co-existing animal species. Periods of rapid change in prey populations offer important opportunities to study the relationship between predators and their prey. In particular, such studies can yield information on the functional response of predators to a changing prey environment and the role of prey dynamics in the regulation of predator population size.

Habitat is the most valuable variable in ornithological studies as it provides food and cover essential for the survival of the population (White and Garrott, 1985). Habitat is an area containing or influenced by the suitable resources and environmental conditions that determine the presence, survival and reproduction of a population (Morrison et al., 1998). Cody (1985) described habitat as areas where an organism’s need for food and shelter are met. Habitat selection and use by birds is fundamental in understanding their biology and management and it has been one of the most well studied aspects of avian biology, particularly as habitats are altered by human activities (Pain and Pienkowski, 1996).

According to the optimal foraging theory, animals may use the areas offering higher food extensively (Stephens and Krebs, 1987). By using the most productive patches, birds may have a high ingestion rate, allowing to reduce the time exposed to predators and having more time to other activities. However, some authors have obtained contradictory results also. They have not found clear relationship between bird abundance and food availability (Wiens, 1984 and Herrera, 1988). The ability to exploit food resources is one of the most frequently suggested reasons for habitat selection by birds (Caraco, 1980) and would be expected to be primary basis for selection of foraging habitat.

Population studies have been traditionally used to monitor large scale, long term changes in avian population and to assess both habitat quality and the responses of birds to both management practices and natural and human caused environmental changes (Wiens, 1989). Species composition, abundance and behaviour of birds are known to vary seasonally (Morrison et al. 1980). Some species are permanent residents in an area, others occupy an area only during winter or summer months. In this chapter, seasonal variations of wetland bird community in the Kole wetlands are described in terms of species richness, abundance, diversity and density.

METHODS

Seasonal pattern

The study area has three distinct seasons viz. dry season (December to April) wet-I, the period of southwest monsoon (May to August) and wet-II, the period of northeast monsoon (September to November). Based on the arrival of migratory birds, the months are divided into migratory season (September to March) and non-migratory season (April to August). Occurrence of birds in each month obtained through the daily census data was used for the seasonality analysis. Monthly changes and seasonal changes of the community were analysed. Species richness, abundance, diversity indices of each season and also in migratory and non-migratory season were calculated and presented. Population fluctuations of 36 wader species in the four intensive study areas during three migratory seasons were estimated. Apart from these, detailed information on the population fluctuation of selected bird species was presented.