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Introduction

India is known to be one of the 12 most important mega diversity centers of the world. India with varied habitats harbours a rich bird life. Aves constitute the most important phylum of animal kingdom. Avifauna is an important biological resource and a component of natural ecosystem. The Indian region with varied habitat harbours an incredibly rich bird life. Moreover, birds were regarded as the indicators of environment. The study of bird communities has been a major area of research in community ecology.

Migration can be defined as the seasonal movement of species from one place to another. Bird migration has been defined in a very appropriate way by Marten Duncan-"Many species in the colder regions of the world seek on the approach of winter, other lands, where more congenial conditions prevail and suitable food in sufficient quantity may be found. The return of spring, however, sees them once again on the wings, making their way back to their old breeding grounds and even, as a general rule, seeking the same nesting site. The autumn migration as a whole may be said to be a journey from the arctic and temperate zones of Northern hemisphere to countries lying to the equator in a more or less Southerly direction i.e. as for ming a general southward movement. In the Northern Europe, there is a good deal of migration taking place in west to east direction."

The present study was carried out to highlight the importance of Lake Mansar which is important from habitat point of view for the aquatic migratory birds. Moreover, Lake Mansar has also given the status of Ramsar site.

A review of literature reveals that migratory ducks use non-breeding habitat for seven monthsof a year but the importance of wintering birds has been scarcely investigated. But contrary to this abundance of work has been done on breeding biology of aquatic birds. Among these workers are Danell and Sjoberg1(1978), Reedet al.²(1983), Kear³(1979), Giles⁴(1989) and Guzij⁵(1992). The population size, distr i bution and ecological parameters required for post breeding waterfowl are still not well studied; Stewartet al.⁶(1958) and Fredrickson & Drobney⁷(1979), As far as our knowledge about the ecology of wintering habitat of the waterbirds is concerned, it is still very little (Anderson and Batt⁸(1983).

So the aim of present work is to find out the number of migrator y species in Mansar especially of the aquatic waterfowls. Besides this, the aim of this present paper is to gather sufficient information regarding the ecology of waterfowls like habitat preference, feeding and sexual dimorphism.

Material and Methods

Study Area

The study area, village Mansar lies between 30° 45' 5" to 33° 42' 36" North latitudes and 75° 8' 32" to 73° 9' 8" East Longitutes. It is situated about 65 km North-East of Jammu city. The elevation of Lake Mansar is 666 m above sea-level in the Shivaliks terrain of Jammu. Lake Mansar is one of the oldest lakes located in Jammu Shivaliks, fringed by forests and which harbours an interesting aquatic biota. It is situated along the North - South flyway Palearctic-Oriental migrator y route of Waterfowl. Lake surface area is about 0.58 Km² and Lake Basin area is 1.67 Km². The maximum depth is 38.25 m. The lake mean width is 490 m and means depth is 20.23 m. Lake Mansar is warm monomictic waterbody. The lake is a structural feature created by Mansar Fold, occurring as a tight fold. It is surrounded by number of villages and seasonal Choes and Khads.

Methodology

The study area was surveyed for recording diversity and population dynamics of wintering birds by applying Line transect method, Sale and Berkmuller⁹(1988) and Point transect method, Verner¹⁰(1985). Census were made weekly during the study period at different hours of the day. Themain transect made during the investigation was the circumference of lake. The abundance of migratory birds was recorded by observing species with the help of Binoculars (Bushnell 7 x 50 U.S.A made). Photography was done with the help of Canon T-70 camera fitted with 300mm zoom lens, digital camera and video camera in order to identify the avian species.

Table 1: Showing the systematic list of migratory avifauna of Mansar along with their status. Click here to view table

Results and Discussion

The total number of bird species recorded was enlisted in (Table 1). Among the 21 species recorded, 8 species constitute the migrator y waterfowls. These utilize the wetland either to tide over winter for a short period during their migratory spell. Coots were the first to arrive in the study area during the month of October. Mallard, Shoveller, Gadwall, Common Pochard, Coot, Pintail, Wigeon and Tufted Pochard were found to stay in the study area during winter months (October to March). An increase in the number of resident birds i.e.White Breasted Waterhen, Moorhen, Little Egret and Pond Heron was also observed showing a case of local migration. The increase in the number of these species for wintering months may be attributed to availability of space and food resources. Other migratory species includes White Wagtail, Grey Wagtail, Indian Grey Shrike, White Capped Water Redstart, Darter, Night Heron, Grey Heron, Black Bittern and Steppe Eagle. These were sited in the months of October, November, December and January.

During the migration period, waterfowls showed gregarious behaviour besides daily activities like feeding, resting, dabbling and preening. Similar findings were made by Tamisier¹¹(1972). Among all these activities, the main were found to be resting as well as feeding. This observation goes well with that of Hepp¹²(1982).

A sudden decline was observed in the diversity as well as population dynamics of migratory avifauna in Mansar. During the year, 2006-2007 the decline was upto such an extent that only 2 species of migratory waterfowls i.e. Mallard and Coot used to visit Lake Mansar (Table 2). This sudden change was attributed to a number of anthropogenic activities which still prevails there. If these activities get promoted, it may be possible that in the near future no migration will take place which will change the status of the waterbirds as well as also leads to wretched condition of this attractive spot. Anthropogenic factors prevailing in Mansar includes: Removal of vegetation cover, introduction of exotic carps, diversion of water channel which effects the level of lake water, draining of lake water, conversion of paddy fields for construction purpose, washing of clothes, cattle bathing and boating. Moreover, implementation of mobile phone towers by the telecom department also serves as a criterion for the decline in the migratory rate of waterfowls as these towers alters the migratory routes.

Table 2: Showing Population Dynamics of Migratory Avifauna of Mansar during Wintering Months of Year 2004, 2005, 2006 and 2007 Click here to view table

Acknowledgements

The authors are thankful to the Depar tment of Zoology, University of Jammu, Jammu for providing various facilities to carry out the present study.

References

1. Danell K和Sjoberg K,栖息地选择breeding ducks in Boreal lakes in Northern Sweden.Viltervy.(1978)10:161-190.
2. Reed, T.M., Landslow, D.R. and Symonds, F.L., The breeding waders of the Caithness flows.Scot Birds(1983)12:180-186.
3. Kear, J., Studies on the development of young Tufted duck .Wildfowl(1970) 21:123- 132.
4. Giles, J., Experiments on substrate choice and feeding efficiency of downy tufted ducklings, Aythya fuligula.Wildfowl(1989) 40:74-79.
5. Gyzil, A.I., Mallard (Anas platyrhynchos) on lake Sinver (Mezhigorsky district of the Zakar patsky region) in the Ukrainian Carpathians.Vesto. Zool. No.2, pp.83(1992).
6. Stewart, R.T., Gies, A.D. and Evans, C.D., Distribution of population and hunting kill of the Canvasback,J.Wildlif. Manage.(1958)22:333-370.
7. Friedickson, L.H. and Drobney, R.D., Habitat utilization by post-breeding waterfowl, In: Waterfowl and Wetlands. The Wildlife Soc. Madison Wis., pp.(1979) 119-131.
8. Anderson, M.G. and Batt, E.D.J., Workshop on the ecology of wintering waterfowl.Wildl. Soc. Bull.(1983)11:22-24.
9. Sale and Berkmuller. , Manual of Wildlife Techniques for India. Food and Agriculture Organization of the United Nations, Dehradun. (1998)
10. Ve r ner, J., Assesment of counting techniques.Current Ornithology.(1985)2:247-302.
11. Tamisier, A., Rythms nycthemereaux des sarcelles d'hiver pendant geur hiver mage on CamargueApavda.(1972)40:107-135.
12. Hepp, G.R., Behavioural ecology of waterfowl (Anatinae) wintering in Coastal North Carolina.Ph.D. Thesis, North Carolina State Univ. Releigh, N.C. (1982).