A JOURNAL OF COMPOSITION THEORY ISSN : 0731-6755

Foraging Behaviour of Anastomus oscitans in Different at Sembanarkoil Region, Nagapattinam District, Tamil Nadu,

Thangarasu Meganathan*, Paul Jeevanandham PG and Research Department of Zoology, T.B.M.L.College, Porayar - 609307, TamilNadu, India. *[email protected]

Abstract- Foraging behavior of Asian Anastomus oscitans in different habitat was studied in 2017 and 2018 at Sembanarkoil region, Nagapattinam district, Tamil Nadu, India. Considerable variations of foraging behaviour were observed in different habitat. Foraging activities of pace, probe and capture rates were higher rates observed in Agriculture habitat in compared with riverine habitat. The Asian Openbill Stork were more prey successful obtained in Agriculture habitat. Student t –test was applied and statistically significant was found mean of prey successful rate at riverine and agriculture habitat (t=-7.15, P=0.000 in 2017 and t=-5.34, P= 0.000 in 2018) but not significant with riverine habitat and stream habitat (t-test) were recorded (t=-0.29, P=0.76 in 2017 and t=-1.26, P=0.21 in 2018). The flock size and prey success rate in different habitat were showing positive correlation. The Principal Component Analysis (PCA) was performed in relation to foraging variables like month, habitat, prey size, flock size and prey availability determined foraging success. The first two principal components (PCs) accounted for 62.2% in 2017 and 60.7% in 2018 of the total variation in foraging variables. The foraging success was highly correlated with flock size and availability of prey during the study period.

Key words: Asian Openbill Stork, Foraging, Habitat, Prey success, flock size, availability of prey.

I. INTRODUCTION Many large wading and their obtaining prey varies in relation to biotic and abiotic factors including the body size, age, sex, fitness of individual (Kushlan1981, Hollander et al. 2013). The availability of resources is varying across numerous scales of space and time (Urfi, 1998, 2003). Therefore, choosing of feeding habitat and the period of forage in particular habitat is an important in life time (Bjørneraas et al. 2012,Hollander et al. 2013).It is one of the important tools for indicated the habitat quality (Munguia et al., 2005, Güitrón-López et al. 2018). Rich give a higher fitness to the organisms living there where „poor‟ habitats give lower fitness (Johnson 2007). How rich and poor are defined is also of importance for survival offspring and adult (Meganathan and Urfi 2009). The quality of the habitat has many variables such as food availability, water depth, vegetation cover, predator occurrence, easiness of defence, distance to human settlements and many other abiotic factors (Raynor et al.2017). are globally nineteen (Hancock et al.1993). There are nine species of stork present in India (Ali and Ripley 1994). In recent decades foraging ecology of storks have been studied in different region of India (Maheswaran and Rahmani 2002, Sundar 2006, Kalam and Urfi 2008, Ishtiaq et al.2010, Anam et al.2016, Meganathan and Jeevanandham 2019 a,b). Asian Openbill Stork Anastomus oscitans is a large wading in the stork belongs to the family ciconiidae. It is found mainly in the Indian subcontinent and Southeast Asia (Hancock et al.1993). It is very commonest stork in India feeding on molluscs, crabs and small fishes (Ali and Ripely 1974, Anam et al.2016). In this region there is no information available on the foraging ecology of Asian Open bill stork therefore the present study will be useful for to understand the foraging behaviour of Asian Open bill stork in different habitat. Foraging habitat is likely to be significant for developing management and conservation action plan. The main objective of this study was to determine the variation of foraging behaviour in relation to different habitat and described the foraging success rate in relation to foraging variables like availability of prey, prey size, season and flock size.

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II. MATERIALS AND METHODS A. Study Area Nagapattinam District is one among 35 Districts of Tamil Nadu, India and area covered is 2715.83 sq. km. It is bounded by Bay of Bengal on the east, the Palk Strait on the south, the Thiruvarur District on the west and Cuddalore District on the north. The present study was carried out in Sembanarkoil region covering about 32sq. km at Tharagambadi Taluk, Nagapattinam District (11º 06' N, latitude 79º 44' E longitude) in the Cauvery Delta of Tamil Nadu (Fig.1). Study was conducted in different habitat like the riverine, pond, streams, marshy and agriculture. The area is dominated by wet agricultural lands with paddy (Oryza sativa) being the predominant crop cultivated. Other crops also cultivated include cotton, sugarcane, groundnut, banana, pulses and other cereals. Four seasons were distinguished at the study area based on rainfall viz., monsoon (October-December), post-monsoon (January-March), summer (April-June) and pre-monsoon (July-September). In general January is the coolest month and May is the warmest month in the study area (Meganathan and Jeevanandham 2017a).

Figure-1 showing the map of India (A) followed by TamilNadu (B), Nagapattinam District (C) and Study Area (D) covered about 32 sq km in Sembanarkoil region along with Cauvery and Manjalaru rivers (sources from Meganathan and Jeevanandham 2019a). B. Methods Present study was conducted from January 2017 to December 2018. During the study period the data collected at time of early in the morning to till the late evening 0600h to 1800h. A flock size was identified by pointing the binoculars (7X50) towards the flock and by counting the number of individuals. Flock size was estimated by number of birds present within the radius of 10 meters of focal bird (Meganathan and Jeevanandham 2017a).Prey availability was estimated by after completing the foraging by birds. At each foraging the sampling was estimated1 m2 quadrate and in each quadrate number of molluscs including broken shell, live specimen and crab species were estimated. Prey species of Asian Openbill stork were identified in this region such as species, bivalves, crab, small fish etc.,(Meganathan and Jeevanandham 2019b). Prey size was measured by using the Vernier Caliper and prey size was total length of the prey (Meganathan and Jeevanandham 2017b). Type of Habitat, time of day and other relevant parameter were also recorded during the data collection. Habitat type was categorized into five different habitats viz., riverine, stream, pond, marshy and agriculture as followed by Pramanik et al. (2016). Behavioural observation was recorded using the focal sampling method (Altman, 1974). Observation was made periodically in different hours of day at foraging site using 7X50 binocular, and the duration of observation was five minutes. A digital stop watch and hand tally counter were used to recorded number of the pace, probe, capture and number of prey success (Biljlsma and de Roder 1991). Prey capture and prey success were counted with hand tally counter for each five minutes of feeding bout. Prey success and Prey capture rate was estimated by number of preys caught per minute (Anam et al.2016). C. Data Analysis Foraging behaviour of Asian Openbill Stork were analysed by using MINITAB software. Descriptive statistics were computed for all relevant data. Among the different habitat the foraging behaviour were analysed by using a One- Way ANOVA test. Student t-test was used for comparing mean of the prey success rate between habitat. Variation

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of prey success rate of Asian Openbill Stork in different habitat was represented a bar diagram for during study period. Pearson correlation was applied for the relationship between flock size and prey success rate in different habitat during study period. Principal Component Analysis (PCA) analysed were performed to foraging success in relation to different habitat, month, prey availability, prey size and flock size of Asian Openbill Stork.

III. RESULTS A. Foraging behaviour During the study period the foraging behaviour for 1065 minutes in 2017 and 895 minutes in 2018 of successful foraging bout were observed in different habitat. Considerable variations were observed the foraging behaviour of Asian Openbill Stork in different habitat by One-Way ANOVA (Table-1). The mean value of paces, probes and captures rate (attempts) were higher in marshy and agriculture habitat in compared with riverine, stream and pond habitat (Table-1). The prey success rate was higher in agriculture habitat and the mean value was found to be 1.61±0.81 (51) in 2017and 1.13±0.67 in 2018 and lower prey success rate was observed in riverine habitat in study period 0.61±0.51(42) in 2017 and 0.46±0.41(36) (Fig-2). Significant difference the foraging success rate between riverine and agriculture habitat was noted (t-test; t=-7.15, P=0.000 in 2017 and t=-5.34, P=0.000 in 2018). And prey success rate compared with riverine habitat and stream habitat was not significant difference (t=-0.29, P=0.769, in 2017 and t=-1.26, P=0.212 in 2018). The relationship between the flock size and prey success rate was positively correlated with different habitat. As the flock size increased the foraging success or prey success of Asian Openbill Stork also increased during study period (Fig-3). TABLE 1 Foraging behavior of Asian Openbill Stork in different habitat during the study period Type of Habitat Year Foraging behaviour Riverine Stream Pond Marshy Agriculture F φ P* Sample Size 42 36 42 42 51 Pace/m 1.47±0.56 0.85±0.26 1.27±1.09 2.53±1.40 7.89±5.30 52.40 0.000** 2017 Probe/m 7.94±2.84 4.45±1.39 5.01±4.39 13.21±7.33 35.95±12.81 14.98 0.000** Capture/m 1.07±0.65 0.83±0.40 1.07±0.65 1.30±0.73 1.90±0.93 14.98 0.000** Sample Size 36 30 35 36 42 Pace/m 1.40±0.53 0.81±0.26 1.68±1.27 3.11±2.01 7.89±6.56 28.51 0.000** 2018 Probe/m 7.15±2.00 4.56±1.40 8.19±5.31 19.12±11.91 32.06±17.33 47.06 0.000** Capture/m 0.93±0.57 0.85±0.36 1.12±0.68 1.35±0.77 1.77±0.92 10.43 0.000** One-Way ANOVA, *Significant level= **P<0.001.

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Fig.2. Prey Success Rate of Asian Open bill Stork in relation to different habitat during the study period from 2017 to 2018.

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Fig.3. Relationship between the flock size and prey success rate/minutes of Asian Open bill Stork during study period from 2017 to 2018.

B. Foraging success The first two principal components (PCs) accounted for 62.2% in 2017 and 60.7% in 2018 of the total variation in foraging variables. The first principal component accounted for 37% of total variance. All values were positively correlated except that month and prey size. The high value on PCA to foraging success of Asian Openbill Stork with flock size followed by prey availability was noted. The second component accounted for an additional 25% of total variance except for month was the other parameter positively correlated. The highest correlation was with prey availability. When PCA analysis was applied to the 2018 data, the first PCA accounted for 35% of total variance (Table-2). Similarly, in 2017 all the parameter of PC1 had positive value except month and prey size. The PC2 accounted for 26 % of total variance and PC3 accounted for an additional 20% of the total variance. Factors like prey size and prey availability were negatively correlated. The two variables were positively correlated in PC1 and negatively on PC2 (Table-2). TABLE 2 Factor loadings of traits in the Principal Component Analysis (PCA) of foraging success in relation to foraging variables of Asian Openbill Stork during the study period. Year Parameter PC1 PC2 PC3 PC4 PC5 2017 Month -0.055 0.059 0.981 -0.087 -0.156 Habitat 0.475 0.491 0.015 0.681 -0.263 Prey Availability 0.594 -0.317 -0.081 -0.417 -0.605 Prey size -0.114 -0.782 0.074 0.595 -0.123 Flock size 0.637 -0.206 0.162 -0.019 0.725 Eigen Value 1.851 1.258 1.017 0.551 0.321 Cumulative % 0.370 0.622 0.825 0.936 1 2018 Month 0.051 0.225 -0.962 -0.032 -0.144 Habitat 0.428 0.516 0.192 -0.695 -0.173 Prey Availability 0.626 -0.205 0.065 0.408 -0.629 Prey size -0.014 -0.781 -0.141 -0.588 -0.155

Flock size 0.650 -0.177 -0.118 0.055 0.728 Eigen Value 1.7865 1.2496 0.9988 0.604 0.361 Cumulative % 0.357 0.607 0.807 0.928 1

IV. DISCUSSION & CONCLUSIONS The present study clears the foraging behaviour of Asian Openbill Stork and indicates the increase in the pace and capture rate resulted in the increase of prey success rate as well. Therefore, spending more time at foraging ground increases the obtaining their food. Anam et al. (2016) stated that in agriculture habitat the success rate is low, when compared to marshy grassland and habitats. Meganathan and Jeevanandham (2019a) reported that the smaller size prey was found in agriculture habitat and large size of prey in riverine habitat. Present study clearly indicates that optimising the foraging activities of Asian Openbill Stork at agriculture habitat, smaller the prey size increases the prey success rate. Further study is needed to explore the variation of prey size in relation to different habitat, particularly with special reference to agriculture habitat in this region. Foraging success of Asian Openbill Stork was varied in relation to different habitat. Agriculture habitat showed more prey success rate in compared with remaining habitats. This variation is directly associated with availability of prey and rich prey availability present in agriculture habitat. Majority of feeding habitat preference by Asian Openbill Stork in agriculture habitat was reported by Meganathan and Jeevanandham (2019a). Foraging success in relation to water level is highly correlated with large wading birds especially in fish eating birds (Frederdick and Collopy 1989, Maheswaran and Rahmani 2002, Kalam and Urfi 2008). Meganathan and Jeevanandham (2017a) noted a increase of flock size in relation to the availability of prey in this region. Similarly, present study also identify that prey success rate is directly in relation to availability of prey and flock size. Flock size is playing a vital

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role against the predator and human disturbance of foraging sites. Flock size is more important as it increases the prey success rate and obtaining higher benefit when compared with the solitary foraging (Kersten et al.1997).

V. ACKNOWLEDGEMENT We thank the Principal, HOD Zoology, T.B.M.L. College, Porayar for providing necessary facilities during the study period.

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