CONTENTS-
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusion
Acknowledgments
References

The present investigation was carried out during January and February 2002 on 88 irrigation tanks. These 88 tanks were chosen out of the 433 tanks surveyed 10 years ago in the Tiruvannamalai district. The objective of the study was to   ascertain the likely changes in bird population and threats. The various parameters like water level, encroachment, siltation, social forestry activity, infestation by weeds, submerged vegetation, agricultural practices carried out, nature of water surface, colour of water, hunting and trapping of birds and socioeconomic status of the people were investigated.   Altogether 212,227 birds belonging to 69 species were recorded.   The density of birds, which was 28.51 birds/ha during the erstwhile study has marginally dropped to 25.04 birds/ha during the present investigation. In the present study only 25 tanks became full and the quantum of water received by other tanks varied widely. Almost all the tanks suffer from siltation and encroachment. In 56% of the tanks, which were brought under social forestry activity, the area covered ranged from 10 to 75%. 70% of the tanks that suffered   weed infestation during the previous investigation has increased by 13% now and the extent of infestation ranged from 10 to 100%. Except 10 tanks, which had sparse submerged vegetation, all other tanks had moderate growth. The hunting and trapping of birds, which took place in 15% of the tanks during the previous study has increased by 5% over the years.

The freshwater wetlands are one of the highly productive ecosystems. They play a vital role in the survival of many species of flora and fauna, including human beings. Despite their great values, the wetlands are getting deteriorated all over the world (Maltby, 1986).

            In India, about 65000 freshwater wetlands   occur covering 4.5 million hectares (Anon, 1990).   In Tamil Nadu, 39000 irrigation tanks are found, which constitute 17 per cent of the irrigation tanks found in India.   Even though irrigation tanks, irrespective of their size, have immense economic and ecological values, (especially ornithological values), they   have been neglected for a long time.   A large number of researchers have   worked   on the coastal wetlands and protected freshwater wetlands in relation to birds in India (Ali and Hussain, 1982, Ali and Sugathan, 1984, Sampath, 1989, Vijayan, 1991, Sampath and Krishnamurthy, 1993, Kar and Sahu, 1993).   But, research pertaining to irrigation tanks and their bird population is very scanty (Chakrapani et al., 1990, Perennou and Santharam, 1990, Sampath, 1993 and 1996 and Parasharya et al . 1996).   The present study was carried out during January and February, 2002 on   88 irrigation tanks.   These 88 tanks were selected from the 433 tanks surveyed between 1991 and 1993 in the Tiruvannamalai district. to the objective of the study was to ascertain the likely changes in the bird population and the magnitude of threats on the tanks over the   past 10 years.   The data collected from the 88 tanks during the present investigation have been compared and discussed with the data collected from the same 88 tanks surveyed 10 years ago.

2.1 Tiruvannamalai District

This study was carried out in the Tiruvannamalai district (11 o 96'N to 12 o 90'N and 78 o 69'E to 79 o 78'E) of Tamil Nadu. This district, which is located   in the northern part of the State,   has a total geographical area of 6355.61 sq. km with six taluks such as Arani, Chengam, Cheyyar, Polur, Tiruvannamalai and Vandavasi. Tiruvannamalai is the district headquarters. This district is bordered in the east by Villupuram and part of Kanchipuram district, west by Vellore and part of Dharmapuri district. Further, in the north it is bounded by Vellore and part of Kanchipuram districts and in south by Villupuram and part of Dharmapuri districts (Figure 1).   Most parts of the district have a hilly terrain with sparse dry deciduous forests.   The total human population is nearly 25 lakhs. This district gets maximum rainfall from northeast monsoon (October to December) and scanty rainfall from southwest monsoon (July to September). The annual mean rainfall in this district is 1500 mm.

2.2 Irrigation Tanks

The total waterspread area of all the 1900 irrigation tanks found in this district constitutes 10% of its geographical area.    The waterspread area of these tanks ranges from 5 to 767 ha.   Except a small number of tanks, which are rainfed all other tanks are either fed directly by the river or indirectly through other tanks in series on the upstream.   Among the 88 tanks surveyed, the number of tanks in the six taluks viz., Arani, Chengam, Cheyyar, Polur, Tiruvannamalai and Vandavasi are 13, 8, 26, 15, 16 and 10, respectively (Table 1).   Out of the 88 tanks, the water spread area of each of the 34 tanks is above 100 ha and the total water spread area of all the 88 tanks is 8492 ha.

2.3 Bird Census

The irrigation tanks were surveyed successively each day.   The number of tanks surveyed in a day depends on the size of the tank, nature of bird population, accessibility and the distance between the tanks.   Bird census was carried out   using a pair of binoculars (10 X 50) by walking over the bund around the tanks.   In the bigger tanks spotting scope (16 X 50 X 50) was used to census the birds. All the birds encountered were enumerated.   Apart from   bird census, important parameters, which determine the health of the tanks like water level, social forestry activity, infestation by weeds, submerged vegetation, magnitude of siltation, water colour and nature of water surface were studied.   In addition to these variables, information on the number of borewells found in the   catchment area, source of water to the tanks, year of modernization, extent of encroachment, agricultural activities   in the catchment   and   utilization of tanks for other purposes and hunting and trapping of birds were collected by interviewing the people of the area.

3.1 Bird Population

3.1.1 Abundance of Bird Groups

  The 69 species of birds recorded have been categorized into 12 groups.   They are, grebe (1species), cormorant (1 species), darter (1 species), herons (4 species), egrets (4 species), stork (1 species), ibises (2 species), ducks (11 species), coot (1 species), shorebirds (31 species), gulls and terns (7 species) and ‘miscellaneous' (5 species).

            Among the 212,722 birds belonging to 12 groups of birds recorded in the present study for the entire district, the group ‘ducks' formed a major component of 68.55%, followed by the   ‘shorebirds' (14.38%), ‘egrets' (4.01%), ‘cormorant' (3.75%), ‘coot' (3.26%), ‘grebe' (2.14%), ‘herons' (1.76%), ‘stork' (0.30%), ‘miscellaneous' (0.17%) and ‘darter' (0.047%).    The 242078 birds belonging to 71 species recorded in the previous study have been formed into the same 12 groups.   Similar to   the present study, in the previous study also the group ‘ducks' constituted a greater percentage of 64.23.   The second largest group ‘shorebirds' formed 15.27%.   The other groups such as ‘egrets', ‘cormorants', ‘grebe', ‘coot', ‘herons', ‘gulls and terns', ‘stork', ‘ibises', ‘darter' and ‘miscellaneous' were in the descending order of 6.23, 4.16, 3.30, 3.25, 2.45, 0.36, 0.33, 0.15, 0.13 and 0.13, respectively.   The percentage composition of 12 groups of birds in each of the taluks for both the studies showed a similar pattern , as indicated   for the entire district.

3.1.2 Density of Birds

   Among all the taluks the highest population of 100473 birds was recorded in Cheyyar taluk and the number of species also was the highest in the same taluk.   While the density (birds/ha) of birds for the entire district during the present study was 25.04 birds, it was 28.51 birds for the same number (88) of tanks 10 years ago.   The reason for   the slight fall in the density of birds by 3.47 could be attributed to the drying   of a large number (29) of tanks during the present survey and also a general decline in the quality of the tanks in several spheres during the last ten year period. In the present study among all the taluks the highest density of 40.67 birds was registered in Vandavasi taluk and the lowest density (7.73 birds) was recorded in Chengam taluk (Table 1).   The reason behind recording   highest density of birds in Vandavasi taluk could be attributed to the presence of water in all the tanks but for one.   The lowest density (7.73 birds) registered in Chengam taluk could be ascribed to decreased water levels of 50% of the   tanks surveyed.   Relatively higher density of 28.51 birds recorded for the entire district during the previous study could be due to the presence of water in a large number (82) of tanks. re.   The record of the highest density of 54.75 birds in Polur taluk, during the previous study could be due to the availability of water in all the 15 tanks surveyed The comparatively larger density of birds for the entire district in the previous study and   in the two taluks (Cheyyar and Vandavasi) in the present study   indicate that birds prefer tanks as long as they   have enough water for their survival.

Table: 1 Number of tanks surveyed and their   profiles

3.1.3. Abundance of Bird Species

The percentage composition of different species of birds in each group for the entire district gives the nature of dominance of bird species.   Among the four species of herons viz., Grey Heron, Purple Heron, Indian Pond Heron and Black-crowned Night heron, the percentage composition of Indian Pond Heron was the highest (75%), followed by Black-crowned Night Heron (15.43%), Grey Heron (8.04%) and Purple Heron (1.52%). Among the four species of egrets, Little Egret was found to be dominant with 44.19% of the total egret population of 8535 .   The percentage composition of Cattle Egret, Intermediate Egret and Great Egret were 42.26, 11.09 and 2.45%, respectively.   In the group ‘ibises', out of 1164 birds belonging to Asian White Ibis and Glossy ibis, the former comprised of 47.77% and the latter 52.23%.

Out of the 11 species of ducks recorded with the total population of 145816 birds, Northern Pintail outnumbered all the ducks species with the percentage composition of 52.27.   The percentage compositions of other species such as Northern Shoveller, Common Pochard, Garganey, Common Teal, Cotton Pygmy-Goose,   Eurasian Wigeon, Tufted Pochard, Mallard, Spot-billed duck and Lesser Whistling duck were in the descending order of 12.83, 8.31, 7.92, 7.85, 3.43, 2.14, 1.06, 0.89, 0.09 and 0.09, respectively.   The ‘unidentified ducks' comprised of 3.08%.

In the group ‘shorebirds' which consisted of 31 species with a population of 30664 birds, the Black-winged Stilt constituted 22.13%.   The other most abundant species were Wood Sandpiper (16.23%), Little Stint (10.98%), Little Ringed Plover (8.54%), Green Sandpiper (6.80%), Pacific Golden Plover (5.23%), Kentish Plover (5.18%), Red-wattled Lapwing (3.45%), Marsh Sandpiper (3.33%), Common Snipe (3.09%), Black-tailed Godwit (2.51%), Grey Plover (1.89%), Common Sandpiper (1.86%) and Lesser Sandplover (1.68%). The ‘unidentified shorebirds' formed a small percentage of 1.63.   The remaining 17 species like Stone Curlew, Yellow-wattled Lapwing, Indian Courser, Small Pratincole, Large Sandplover, Bar-tailed Godwit, Whimbrel, Eurasian Curlew, Spotted Redshank, Common Redshank, Common Greenshank, Terek Sandpiper, Pheasant-tailed Jacana, Temminck's Stint, Curlew Sandpiper, Broad-billed Sandpiper and Ruff collectively constituted the remaining percentage.   

            In the group ‘gulls and terns' the number of birds recorded was 2286.   Brown-headed Gull, which is the only species represented in this group constituted 6.99%.   Among the 6 species of terns the Gull-billed Tern formed the largest percentage of 71.78.   The other dominant species were, Whiskered Tern 9.84% and Common Tern 6.74%.   Another 3 species such as Caspian Tern, River Tern and Little Tern comprised   the remaining percentage of 4.65.

            In the group ‘miscellaneous birds' among the total population of 291 birds, the dominant species was Watercock, which constituted 48.45%.   The remaining 4 species such as White-breasted Waterhen, Common Moorhen, Cinnamon Bittern and Black Bittern were in the descending order of 34.16, 9.27, 5.15 and 2.74%, respectively. Though these five species belong to two of the 12 groups, they have not been included with those groups as the population of these five species was very small. The names of all the bird species have been adopted from the publication of the Bombay Natural History Society (Manakadan et al., 1998).         

In the case of species diversity a greater number of 67 species has been recorded in Cheyyar taluk and the lowest number of 34 species has been registered in Chengam taluk.   The reason for such a wider variation in the number of species could be traced to the existence of large number of tanks with water in Cheyyar taluk than Chengam taluk.

            The high abundance of Northern Pintail among the 11 species of ducks and also its presence in   35 tanks may be due to its survival capability in a wide variety of habitats and the availability in abundance of its preferred food materials (Vijayan, 1991 and Sampath 1996).   The   presence of   species like Northern Shoveller, Common Pochard in comparatively greater abundance than other species of ducks could be attributed to the    presence of e deep water habitats in this district (Sampath, 1996).   The preference for deep water habitats by these species has been reported by Vijayan (1991) and Shirazi (1993).

              Among   the 69 species of birds recorded from 59 tanks (remaining tanks dried up, see Section 3.2.1), p ‘herons' Indian Pond heron, was   recorded the maximum   in 56 tanks.    The Black-crowned Night Heron was sighted only in 7 tanks.   In the group ‘egrets' Little Egret, which was the highest in its abundance was recorded in   55 tanks.   The record of Indian Pond Heron and Little Egret in the largest number of tanks in this investigation which is similar to that of the previous studies (Sampath, 1993 and 1996) could be attributed to the wider flexibility in habitat selection (Vijayan , 1991).

            In the group ‘shorebirds' the Black-winged Stilt, which was abundant than all other shorebirds species was encountered in the largest number of 50 tanks.   The other common shorebird species such as Red-wattled Lapwing, Common Sandpiper, Common Snipe, Spotted Sandpiper, Little Ringed Plover, and Kentish Plover recorded were in the descending order of 49, 42, 41, 34, 29 and 28 tanks, respectively.   The occurrence of these species in greater abundance and also in the largest number of tanks could be ascribed to the availability of suitable habitats. The bird species recorded in only one tank were Temmink's Stint and Little Tern. Among the 88 tanks surveyed the highest population of 23511 birds was recorded in Thennampattu tank and the lowest number of 51 birds was registered in Tirumani tank.    Both the tanks are in Cheyyar taluk.

3.2 Factors Affecting Irrigation Tanks

The irrigation tanks, once lifeline for the farming community, were constructed 3000 years ago and managed efficaciously till the end of 19 th century   (Dikshit et al., 1993).   The deterioration of the tanks started from the beginning of the 20 th century.   Now-a-days irrigation tanks are facing alarming threats from several spheres and many tanks have already disappeared.   This is evident from the decline in the extent of irrigated area.   Out of the total cultivable land area in Tamil Nadu, the tanks irrigated 38% of the area in 1950.   But, the irrigated area further shrank drastically and the area irrigated by the tanks was only 23% in 1988.   At present, it is reckoned that it has woefully reduced to 15%.   Though the State government is taking up modernization of irrigation tanks for many years, it has not fetched any desired result.  

3.2.1 Water Level

Among the 88 tanks surveyed, 29 tanks were in a parched state at the time of the survey. Of these 29 tanks, a maximum number of 11 tanks was in Tiruvannamalai taluk, eight in Polur taluk, three each in Arani, Chengam and Cheyyar taluks and one in Vandavasi taluk.   The dry state of tanks in Tiruvannamalai and Polur taluks was due to failure of monsoon. The other four taluks although had relatively lesser rainfall, water from the dams in the upstream helped in augmenting water to these tanks.

Out of the 88 tanks, 25 tanks became full in 2002.   Of the remaining 63 tanks, 12 tanks received about 75% of water, 18 tanks got 50% of water, 7 tanks with 25% of water and the rest of the 26 tanks received less than 25% of water.   These 26 tanks became dry during January – February, the period of the present survey.   Out of the 25 tanks, which had become full in 2002, three tanks viz., Thorapadi big (Chengam taluk), Edapalayam (Tiruvannamalai taluk) and Pulivai (Vandavasi taluk) too dried up due to heavy siltation leading to shallowness, and leaking sluices.

  Despite low rainfall, many of the tanks could have got enough water from the dams upstream had the feeder canals been properly maintained.   Many tanks in this district have not been filled up for many years.   Only eight tanks have got water to their full level successively for the last five years.   A maximum number of 45 tanks have   not received sufficient water to its full level for the past 2 to 5 years..   According to farmers, 30 tanks are rainfed and the remaining tanks are riverfed.   As the tanks are getting deteriorated, farmers have started taking up borewell irrigation.    Apart from   two tanks viz., Azhividaithangi and Kiliyathur (Cheyyar taluk), the catchment areas s of all other tanks, irrigation is being done with a large number of borewells.   The number of bore wells in the catchment areas of the surveyed tanks ranged from 5 to 500.   At the time of the present survey modernization was being done in five tanks.     In other tanks, partial modernisation was done now and then.   In the name of modernization, only repairing of bund is done without paying much attention on complete desiltation, repairing the   feeder canal, removal of encroachments and deweeding.    The farmers of the area when interviewed expressed their anguish on the state of affairs of tank modernization (Sampath, Unpublished work).   It would be worthwhile if the modernization work of the tanks are carried out directly by the concerned department by involving the “Farmers' Society” of the area. Since only a few villages have this society, efforts should be taken for the formation of such societies in all the villages and they should be monitored for   effective functioning.

3.2.2. Agricultural practices

  Agriculture is the primary activity in this district.   The extent of dry and wet agricultural lands in this district is 267644 ha and 74066 ha, respectively.    Intensive cultivation of major crops such as paddy, groundnut, sugarcane is being carried out through out the year.   Other crops like gingely, millets, pulses, tobacco and cotton are also cultivated .   Even though many of the tanks were dry during the period of the present investigation, agricultural activities in the catchment areas of all the tanks were found to be in full swing with water from the borewells.    The crop lands are also used by an appreciable number of birds belonging to the family - Ardeidae, Ciconiidae and Chradriidae. Annual utilization of 5100 tonnes of chemical fertilizers, 500 tonnes of insecticides and pesticides (powder) and 2600 litres (liquid) 10 years ago (Sampath 1993 and 1996) is expected to have increased marginally during the last 10 years.   The usage of large quantum of fertilisers and insecticides and pesticides is feared to cause ill-effects directly on the biota of the croplands, especially birds.   The runoff of large quantum of these fertilizer and insecticides, which ultimately find their way into the irrigation tanks is likely to cause serious impact on the avifauna of the ecosystem (Hug and Kamal, 1993 and Sampath 1993 and 1996).   Though the government is emphasizing that the farmers   should adopt economic and ecofriendly agricultural practices, they invariably stick to the same practice of using large amount of chemical products.   For the continued use of irrigation tanks for generations and for the conservation of their various biotic components, including birds, viable strategies should be evolved in a wider perspective so as to make the people take up sustainable agriculture.

3.2.3 Encroachment

  Apart from 10 tanks, which are known to be free from encroachment all other tanks, suffer from “the encroachment syndrome”.   The extent of encroached land, according to farmers, ranged from 5 to 20%.   In the encroached area of all the tanks,   agricultural activities were   noticed.   Apart from the tank area, the canals, which feed the tanks were also known to have been encroached.   The encroachment of the feeder canal is the root cause for the deterioration of the tanks, as this prevents flow of water to the tanks.   As long as the tanks are getting parched, the extent of encroachment is alarmingly increased.    This could be sensed by comparatively lower figure obtained in the previous study.   The severity of the encroachment of the tank   from this district has been already documented by Sampath (1993 and 1996) and elsewhere by Reddy et al. (1993), Trisal (1993) and Narayan (1994). Apart from taking   survey of the encroached area by the concerned department, retrieving the encroached land and sensitising the people will help protect the tanks and their dependents, including humans.

3.2.4. Siltation

            After a span of 10 years, the enormity of siltation could be realized during the present survey   of all the tanks. While no tank is free from siltation, 15 tanks are assessed as moderately silted and all other tanks are heavily silted.   The severity of siltation was assessed by interviewing the farmers of the area.   The farmers stated that some of the bigger tanks which on becoming full, lasted for 3 crops some 15 to 20 years ago, now lasted for 1 or 2 crops. The magnitude of siltation, for instance was revealed by the people of Vakkadai tank (Cheyyar taluk) when they were interviewed. They said that a rock to a height of 6 feet, which was seen at the center of the tank 20 years ago, has now disappeared owing to siltation.   The extent of siltation is the same for all the tanks in this district.

            The important factors for the siltation of the tanks are, large scale deforestation of adjoining forests, exploitation of catchment area by the removal of trees and overgrazing and the wrong agricultural practices adopted by the farmers. In the research works of Denny and Turyatung (1992), and Scott (1993) they reported similar factor to be responsible for siltation of the irrigation tanks.     The State government has assessed that by the siltation 10 to 40% of the water holding capacity of all the tanks has been reduced.   The degradation of wetlands including man-made wetlands by siltation has been reported by Dugan and Jones (1993) and Sampath (1993 and 1996). It is a welcome measure that the State government is taking up afforestation activities all over the district.  

3.2.5. Social Forestry Activity

The Tamil Nadu government since 1981 has been implementing the ‘Social Forestry Scheme' in the irrigation tanks with several objectives. Among the many species planted, the dominant species are Acacia arbica and Acacia nilotica. The planting of saplings is done all over the watershed area of the tanks. When they grow, the canopy covers the entire tank area. The implementation of this scheme instead of accruing desired benefits, causes serious health hazards to the tanks. As the canopy of the trees covers most part of the tank, it prevents sunlight into the tank resulting in arresting or dwindling the productivity. Also the continued decomposition of leaf-litter makes the tanks shallow, which in turn reduces the water holding capacity and it also accelerates eutrophication. Besides, the utility of the tanks by the birds has been affected in several ways. The coverage of 90% of tanks under social forestry activity 10 years ago has been known to have dropped considerably. Out of the 88 tanks surveyed, 33 tanks were free from forestry activity. Most of the farmers expressed the ill-effects of implementing the social forestry activity in the tanks. The social forestry activity in the tanks has caused deleterious effect to the tanks as documented by Narayan (1994). Further, Bernacsek, (1992) studied the impact of forestry activity on the irrigation tanks. As the social forestry activity in the irrigation tanks is known to be one of the causes for the degradation of the tanks, the forestry activity on the waterspread area should be stopped. Instead, if saplings are planted all along the bund they will, besides strengthening the bund offer an ideal roosting and breeding ground for the birds.

3.2.6 Infestation by Weeds

            Infestation of weeds is one of the major factors for the deterioration of the irrigation tanks.   In the previous studies (Sampath, 1993 and 1996), it was reported that 70% of the tanks have   been infested with weeds. In the present survey the number of tanks infested with weeds have marginally increased by 13%.   The reason for such an increase could be attributed to the prolonged drying up of the tanks for many years.   The dominant weed species were Prosopis spicifera , Ipomoea cornea and Scripus sp. The extent of infestation ranged from 5 to 100%.   The profuse growth of weeds leads to reduction in water holding capacity, decolouration of water and eutrophication.   The tanks such as Kiliyathur (Cheyyar taluk) and Rendiripattu (Polur taluk) have been infested with Prosopis spicifera , all over (100%) the tank area, whereas Sorakolathur (Tiruvannamalai taluk) and Sengunam (Polur taluk) tanks have been infested with Ipomoea cornea in   the entire (100%) tank area and Akkur tank (Arani taluk) has been found infested with Scirpus sp. in the 75% of the tank area.   The parched nature of all these five tanks is a testimony that greater infestation reduces the water holding capacity of the tanks.   Besides, profuse growth of weeds occurs only in the tanks, which are silted heavily.   The infestation by weeds is one of the major factors for the deterioration of the quality of the irrigation tanks (Sampath, 1993 and 1996 and Trisal, 1993).   The farmers across the district are very much concerned about this menace as it deteriorates the quality of the tanks.   Besides, tanks with abundant weeds become unsuitable for birds.   Apart from initiating immediate measures to deweed all the tanks by the government, all efforts should be made to change the attitude of the people of the area in expecting the government in the eradication of the weeds in the future.

3.2.7 Submerged Vegetation

The occurrence of moderate growth of submerged vegetation is essential for the well functioning of any aquatic ecosystem (Vijayan, 1991 and Parasharya et al ., 1996). But profuse growth creates several problems on the health of the tank and its biota.   In this survey, out of the 59 tanks, which possessed water, in a large number of 49 tanks, moderate growth of submerged vegetation was recorded.   In the remaining 10 tanks the growth was sparse.   As all the tanks are seasonal they become dry during summer.   The seasonal nature of the tanks could be a reason for the controlled growth of submerged vegetation. The birds mostly prefer tanks with moderate growth of submerged vegetation.   The common submerged vegetation recorded were Chara zeylanica, Hydrilla verticilliata, Otellia alismoides, Nitella hyalina, Vallisneria natans and Ceratophyllum sp. Besides these, in many tanks emergents like Cyperus alulatus, C.bulbosus, C.pygmaeus, Scirpus supinus, S.lateriflorus and Aeschynomene indica were also recorded.   Comparing with the previous study, not much variation in the occurrence of submerged vegetation in the number of tanks and abundance could be noticed. A comprehensive study on the vegetation mapping of all the bigger tanks should be taken up.   This will help manage the tanks effectively in harnessing the economic and ecological values.

3.2.8. Nature of water surface and water colour

The nature of water surface of the tank is vital for attracting birds.   On the basis of spread of vegetation like submerged, floating and emergents, the tanks have been classified into three types.    They    are “open”, “partially open” and “closed”. Out of the 59 tanks, which possessed water, the water surface of 36 (61.01%) tanks was completely open.   In the remainder 22 (37.29%) tanks, the water surface was partially open.   The weeds and plant species (social forestry as mentioned elsewhere in this work) cover the water surface of the tanks. In only one tank called Paiyur (Arani taluk) the entire water surface has been completely closed by water hyacinth Eichhornia sp.   Except tanks with “closed” water surface, the other two types of tanks are found to be ideal habitat for birds.   In the erstwhile study (Sampath, 1993 and 1996), the number of tanks of these three categories was   found to be the same.   Pertaining to colour of the water, in five tanks the water was turbid, in three tanks the water was black in colour and in another tank it was green in colour. In all other tanks the nature of water was clear.   Among all the tanks only the Purisai tank (Cheyyar taluk) is used for fish culture by the government.

3.2.9. Hunting and trapping of birds

While the deterioration of wetlands is one of the reasons for the declining   bird fauna, the indiscriminate hunting and trapping of birds perpetuated by the nomads and the people of the area are the other threats faced by the bird species.   Incidence of hunting and trapping of birds, which was 15%, 10 years ago has escalated to 20% during the present study. Among the 69 species of birds recorded in the present study, three species such as Indian darter, Asian Open-billed Stork and Asian White Ibis are among the many threatened species in the Asian region (Scott and Pools,1989).   The most common species that fall victim to the vicious activities of the people are the herons, egrets, storks, ducks and shorebirds.   The sale of birds is not uncommon in this region.   The socioeconomic backwardness forces people to eke this sort of living (Sampath, 1993 and 1996).   A similar reason   for the hunting and trapping of birds from the irrigation tanks has been reported by Reddy et al . (1993).    As the many poverty alleviation programmes being implemented now and then by the government offer only an adhoc solace, the only way to eliminate the economic backwardness of the farming community for ever is the effective management of the irrigation tanks. This will   in turn improve   the economic status of the people, eschewing them from hunting and trapping of birds.   As the people are unaware of the role of birds in the ecosystem they should be educated on this front.   Also   the management of tanks and their importance should be included in the school curriculum from the primary stage onwards.

3.2.10 Socioeconomic Status of the People

A considerable increase in the human population could be noticed in this district after 10 years.   The population, which was 20 lakhs (Sampath, 1996) has escalated to 25 lakhs now. Out of this, it is known that 10 lakh people are agriculturists and agricultural labourers.   A notable improvement in the literacy rate has been achieved by this district over the   last 10 years. As 40% of the people are involved in agricultural activities, they fully depend on the irrigation tanks.     Further   people make use of the irrigation tanks for drinking water, domestic chores, collection of aquatic plants, pasture ground, fishing, firewood collection and so on.

Unequivocally,   it can be put forth that the irrigation tanks in this district are getting deteriorated owing to the negligence of the people and governmental apathy.   Added to this woe is the irregular monsoon.   It is firmly believed that if the suggestions offered   in the different Sections of this paper, are taken into consideration, it will deliver the desired results.

            I thank the concerned authorities of Tiruvannamalai district for having provided necessary particulars regarding irrigation tanks.   I express my sincere thanks to Dr.K. Kathiresan, Professor CAS in Marine Biology, Annamalai University and my colleague Dr. R. Alavandar,    Senior Lecturer, District Institute of Education and Training, Vadalur for reviewing the manuscript.

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Secretary,
Society for Environmental Education and Conservation,
2/71, 5 th Cross, Kanakasabai Nagar,
Chidambaram – 608 00.
Tamil Nadu. India.
Email: sampmul@yahoo.co.in