International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 2(4), 39-43, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 39 Causes of Temporal Variation in the Arrival of Asian Open Bill Stork Population: A Case Study of Kulik Wildlife Sanctuary, West Bengal, IndiaPiyal Basu Roy1 and Radha Sah2 Department of Geography, Alipurduar College, West Bengal, INDIA Zoological Society of Assam, Cotton College, Guwahati-781001, Assam, INDIAAvailable online at: www.isca.in Received 24th February 2013, revised 4th March 2013, accepted 16th March 2013 AbstractThe paper is an attempt to identify the causes and pattern of temporal variation of Asian Open Bill Stork (A. oscitans). To understand the status of environmental health of a habitat, the trend of arrival, food and habitat of bird population play innovative role and proper analysis of that has indicated that flood in the river Kulik very adjacent to Kulik Wildlife sanctuary is the foremost cause of temporal variation in the arrival of Asian Open Bill bird population. Apart from the flood, the changing climate, deforestation and anthropogenic factors are also responsible for decline in their arrival. Therefore, such analysis or approach of study does not only reveal the temporal qualitative change experienced by that habitat but also signify the impact of that on influx of bird population along with other species.Keywords: Kulik wildlife sanctuary, Asian open bill stork, temporal change. Introduction The Asian Open Bill Stork (Anastomus oscitans) is a resident colonial breeder. It is a large wading bird of order Ciconiiformes and family Ciconiidae. These birds usually migrate to the lower part of Himalayan ranges and spent about six months for the purpose of breeding that is from July to December. Kulik wildlife Sanctuary is the largest abode of Asian Open Bill population in the world and claim to be the second largest bird sanctuary in Asia. Ornithologically, this bird sanctuary is the largest “Heronary” of open Bill storks as per Bird Life International and Wetland International. The heronary is the place where various species of water birds breed or roost symbiotically. It is defined as the habit of nesting colonially. It is mainly greyish white with glossy black wings, tail and the adults have the beak with a narrow gap formed by the arched upper mandible and recurved lower mandible. The mandibles donot meet except at the tip, and for this reason this species of stork is known as Open Bill Stork. Young birds are born without a gap in the bill and this structure is thought to be an adaptation that aids in handling their main prey of snails (the main diet is Pila globasa). For this reason, it is commonly known as Samukh (snail) khol. The cutting edges of the mandible have a fine brush like structure that is thought to give them better grip on the shells of snails. The mantle is black and the bill is horn-grey. The short legs are pinkish to grey, reddish prior to breeding. Non-breeding birds have a smoky grey back instead of white. Young birds are brownish-grey and have a brownish mantle2,3. Although mostly resident within their range, they make long distance movements in response to weather and food availability. They are usually found in flocks but single birds are not uncommon. The climate change of an area influences the bird population and also the biodiversity of that area. The changes of bird population in any specific locality can be utilized to measure the dynamicity of the ecosystem. Suitable parameters must be devised to understand the eco-health of any habitat. The number of birds has strong link with biodiversity of an area that acts as potential indicator of environmental quality. Good indicators are specialized in their habitat needs, thus reacting rapidly to changes. Asian Open Bill Storks (A. oscitans), have been considered to the most useful indicator of environment health because they are ecologically versatile and live in different type of habitats6,7. The usual foraging habitats are inland wetlands and are only rarely seen along river banks and tidal flats. Birds may move widely in response to habitat conditions. Young birds also disperse widely after fledging. The species is very rare in the Sind and Punjab regions of Pakistan, but widespread and common in India, Sri Lanka, Burma and Thailand. In India it is mainly found in Bharatpur Bird Sanctuary, Rajasthan and Kulik Bird Sanctuary, West Bengal in their breeding time. Quantitative and qualitative changes in their environment, usually effects the bird population. Usually, they are not the indicator of the primary cause of this change. Birds most often respond to secondary changes brought about by the primary causes. Generally, birds are quite consistent in their habitat preferences10. Often the changes in the abiotic regime of an ecosystem, or cause variables, may be overlooked, be too subtle, or be of no interest to be monitored directly11. Bird watching and monitoring of its population is necessary for several purposes of describing environmental conditions. Birds count is required to examine habitat issues or environmental threats12. Study Area: This study wasconducted in theKulik Wildlife Sanctuary, which is about 2 km away from the Raiganj town in International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(4), 39-43, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 40 North Dinajpur District in West Bengal, India. It is situated beside the National Highway 34. The bird sanctuary is located in both the sides of N.H. 34 or Kolkata-Siliguri Highway. This Sanctuary is located along the western bank of the river Kulik between 2535' to 2557' N latitude and 8807' to 8817' E longitude. The area of this sanctuary is around 1.30 km. The core area is about 0.14 km and the rest is buffer area. The sanctuary has a thick canopy of the deciduous trees, which provides the nesting place for Asian Open Bill Stork and other migratory birds like Black Crowned Night Heron, Great Egret, and Little Cormorant etc. The river Kulik, a tributary of Mahananda River, via the river Nagar, flows round a part of the sanctuary and acts as the boundary in its eastern and western parts. The sanctuary has a network of artificial canals connected with the river Kulik 13 . Annual precipitation range varies from 1200 mm to 1550 mm, mean winter temperature from 09C to 23C and summer temperature from 21C to 25C, and humidity more or less 75 were recorded14. Methodology The entire frame of the study has been categorically built on rigorous field survey based on observation in particular. In addition, data has been collected from the secondary sources like official documents of respective departments. However, along with it, some secondary sources of data like books and journals, etc have also been consulted to prepare the paper. The data has been collected from 1985 to 2009. The long term data is important because in maximum time, it is noticed that short term data collection is misleading or inadequate. Obtained information has been mathematically calculated to derive the results. Habitat preferences of Asian Open Bill Storks (A. oscitans): As stated earlier, Asian Open Bill Storks (A. oscitanas), usually forages in inland wetlands and are only rarely seen along river banks and tidal flats. Due to presence of river Kulik in Kulik Wildlife Sanctuary, it becomes an abode for the Asian Open Bill population. The population of Asian Open Bill along with other migratory birds like little Cormorant, Egret, Night Heron are increasing day by day in this Sanctuary. This is due to availability of nesting tree and Asian open bill is found in both the core region and the buffer region because they can tolerate human interference. This is one of the adaptive features of this bird. Location Map of Raiganj (Kulik Bird Sanctuary) N 1 CM TO 5 KM. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(4), 39-43, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 41 If orders and associated families of Asian Open Bill Stork are analyzed, it comes into notice that theAsianOpen Bill StorkA. oscitans), that occupies highest number in the bird population in the study area comes under order ciconiiformes and ciconiidae family and reflects the healthy wetlands15 Discussion Migratory Birds are the key mobile links that contribute to the function of diverse eco-system. This makes migratory birds prime witnesses to global climate change16 The rhythmic patterns of arrival of birds in Kulik Wildlife Sanctuary are phenomenal as well as very much seasonal. The following table shows trend of arrival of Asian Open Bill Stork in the study area. It is found that there is positive growth that is 65% in the Asian Open Bill Stork population of the study area in the year 1989, if compared with the total number of these birds in 1985. But in the year 1993, there is negative growth in Open Bill population that is 45.89% if compared with the total number of their arrival in 1989. But, there is positive growth that is 42.82% in bird population of the study area in the year 1997, if compared with the total number of their arrival in 1993. There is again a positive growth that is 81.66% in bird population of the study area in the year 2001, if compared with the total number of these species in 1997. In the year 2005, there is negative growth in bird population that is 8.37% if compared with the total number of them in 2001 (table 3). In the year 2009, there is a positive growth of 41.26% in comparison with the year 2005. It is amazing to note that there is also negative variation in the arrival of the birds, particularly in the years 1993 and 2005. The negative trend in bird population is the result of flood by the river Kulik. In the year of flood hazard, the arrival of bird’s evidenced massive negative trends, except these years, the area experienced very positive trends in the arrival of those birds. Climate change as witnessed worldwide has compelled several water birds to migrate from adversely affected wetlands to other habitable wetlands for breeding17. Table-1 Asian Open Bill Stork: Range, Habitat and Food habit Name of Bird Range Major Plant species used for building nest Food Habit Asian Open Bill Stork A. oscitans Systematic position: Class- Aves Order- Ciconiiformes Family- Ciconiidae Genus- Anastomus Species- . oscitansOriental realm Ficus bengalensis (Bat) Anthocephalus indicus (Kadamba) Alstonia scholaris(Chhatim) Barringtonia acurangula (Hijal) Ficus glomereta (Dumur) Terminalia arjuna (Arjun) Dalbergia sisoo (Sisoo) Lagerstoemia speciosa (Jarul) Streblus asper (Seora) Trewia nudiflora (Pituli) Molluscs Pila globosa Lamellidens marginalis Fishes Puntius puntii Labeo rohita Clarius batracus Channa sp Amphibians Bufo melanosticus Rana tigrina Other invertebrates Table-2 Temporal variation of Asian Open Bill Stork Year Total no. of Asian Open Bill 1985 24240 1989 39996 1993 21640 1997 30908 2001 56148 2005 51448 2009 72680 Total 297060 Source: Kulik Bird Sanctuary, Official Record Table-3 Percent Difference in Number of Asian Open Bill population between Years1985 1989 1993 1997 2001 2005 2009 % difference of number of birds between the years N1-N2/N1* 100 N2-N3/N2* 100 N3-N4/N3* 100 N4-N5/N4* 100 N5-N6/N5* 100 N6-N7/N6* 100 No. of birds observed N1 N2 N3 N4 N5 N6 N7 24240 39996 21640 30908 56148 51448 72680 65% 45.89% 42.82% 81.66% 8.37% 41.26% Source: Computed by authors International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(4), 39-43, April (2013) Int. Res. J. Environment Sci. International Science Congress Association 42 From the table 2, we can calculate the rate of change in arrival of Asian Open Bill Stork in the study area can be calculated: (P-P)/t R= *100 (P+P)/2 Here ‘R’ = Rate of change is a function of mathematical relationship among the population size at one point of time (P) to the base population at the later point of time (P) and the number of years over the period (t). Table-4 Rate of Change in Asian Open Bill Stork population from 1985-2009 Rate of change (R) Asian Open Bill Stork From 1985 to 1989 12.26 From 1989 to 1993 14.89 From 1993 to 1997 8.82 From 1997 to 2001 14.51 From 2001 to 2005 2.18 From 2005 to 2009 8.55 Source: Computed by authors Temporal rate of change of Asian Open Bill Stork coming in the area under study has been calculated to understand the trend in arrival of those birds and to identify the conditions of environmental quality required for their nesting, breeding and survival. Here, the common assumption is that if the rate of change in the arrival of those species in the study area is lower, there seems to be a deficiency in environmental requirements or micro ecological imbalance and vice versa. From the table 5, if temporal trend in arrival of Open Bill Stork is analyzed it always indicates a fluctuating but positive rate of change although having lowest positive (2.18) rate of change from the year 2001 to 2005, which indicates some negative aspects related to this lower positive growth rate and practically while going into deep study, it comes into notice that those years experienced consecutive occurrence of flood which hindered the arrival of Asian Open Bill Stork because a large number of nest building trees were damaged and their foods particularly snails were washed out. Therefore, breeding of birds is affected by flooding significantly 18. Table-5 Impact of Flood on Asian Open Bill Population Year Asian Open Bill Stork 1992* 47052 1993** 21640 Percentage of decrease/Increase - 4.50 1996* 36392 1997** 30908 Percentage of decrease/Increase -7.42 * Non- Flood year, Source: Computed by authors, **Flood year Let take a view on the impact of floods on the arrival of Asian Open Bill Stork in the area under study. As per the result derived from the table-5, it is keenly realized that there is both positive and negative impact of flood on the bird species that coming here to breed. The overall picture reveals the severe affect of flood on the Open Bill Stork in particular with a sharp decline in their arrival in the flood years. Results show that in 1992, the Asian Open Bill Stork contributed the largest share (47052) in the distribution of total bird population in the area, but declined (21640) sharply in 1993 due to severe flood as was experienced by that area, if total arrival of them is taken into consideration. Similarly, in 1996, the bird population of Open Bill Stork was 36392, that also got reduced (30908) for arrival of flood in 1997. Conclusion Therefore, the overall result and discussion reveal that there is a keen relationship between arrival of Asian Open Bill Stork and occurrence of flood. Flood being mostly a natural phenomenon restricts the arrival of bird population particularly the breeding of Open Bill Stork. This is because of the fact that the nest building trees along with the available food, particularly snails in that micro habitat are significantly damaged and washed out. During heavy rain, nests are destroyed; many nestlings fell down and become easy prey to ground predators. So, some basic observations associated with such trends of their arrival signify that the habitable environmental quality of Open Bill Stork goes down during flood time very significantly. On the other hand, decline of certain species during non flood years resembles the anthropogenic impact on birds consisting of deforestation, drought, hunting, Poaching, killing and such other activities carried out in that sanctuary avoiding the prohibitions of those activities by the forest department in this part. Therefore, planning should be oriented considering both the physical and man-made hazards and implemented in such a way so that these barriers cannot affect nesting and breeding of those species. 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