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Pathak, Chetna P., 2011, “A Study of Ecology of the Piscivorous Birds at Thol Bird Sanctury”, thesis PhD, Saurashtra University http://etheses.saurashtrauniversity.edu/id/eprint/559
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© The Author A STUDY OF
ECOLOGY OF THE PISCIVOROUS BIRDS
AT THOL BIRD SANCTUARY
A THESIS
SUBMITTED TO
THE SAURASHTRA UNIVERSITY
FOR THE DEGREE OF
Doctor of Philosophy
IN
BIOSCIENCES
BY:
Chetna Pathak,
Department of Biosciences,
Saurashtra University,
Rajkot - 360 005,
India.
JUNE-2011 Dedicated to:
My Father-in-law – Late Mr. T. B. Shah
My Sister-in-law – Late Mrs. Rupal K. Pathak
My Niece – Late Chi. Madhvi K. Pathak
My Nephew – Late Chi. Shrinivas K. Pathak ACKNOWLEDGEMENT
Working as a Ph.D. student in Ecology background was a magnificent experience for me. In all these years, many personalities were instrumental directly or indirectly in shaping up my academic career. It was not possible for me to thrive in my doctoral work without the precious support of these personalities. Here is a small tribute to all these personalities.
At the outset, I wish to express gratitude to my guide Prof.
(Dr.) V.C. Soni for his valuable guidance, invaluable advice, cheerful enthusiasm and constant encouragement, without which, it was difficult, rather impossible for me to complete my research work in a respectable manner. I am grateful to him for allowing me some extra time to finish my experimental work.
My special thanks to the Head of the Bioscience Department
Prof. S.P. Singh for providing necessary facilities at the Department.
I express my sincere thanks to Mr. Pradeep Khanna, IFS,
Principal Chief Conservator of Forests, Dept. of Forests &
Environment, Gandhinagar for giving me permission to work in Thol
Sanctuary. I am also grateful to Dr. C.N. Pandey, the former Director of
GEER Foundation for providing me required facilities and I would also like to thanks to the Pollution Control Board and Data
Center,Gandhinagar for their help.
It gives me pleasure to acknowledge with profound gratitude and indebtedness to Mr. Sanat Sothan and Mr. Aaditya Roy for their vigilant guidance in photography.
I express my gratitude to Mr. Jayeshbhai for helping in some statistical calculations.
My special thanks to Mr. Prakash Parmar, Mr. Pathik Shah,
Mr. Kandarp Bhatt for helping me in my computer work.
My sincere thanks to the Department of Forests & Environment for providing some tools for my work and as a Field Co-operative
Mr. Lilabhai, who was always ready to extend his kind help during my field work.
I express my sincere thanks to Ms. P.A. Vadher, Incharge
Principal of Govt. Science College, Gandhinagar for her moral support.
It is my privilege to have my Head of the Dept. Dr. S.K. Patel, my colleagues Dr. Dilip Odedra, Prof. Shital Vyas, Dr. Tarak Thakker,
Dr. Rajkumari Parwani, Dr. Pragna Prajapati, Prof R. N. Maru, Mrs. Dipikaben, Mrs. Bindu, who have provided great enthusiasm and company during my work.
I also express thanks to my colleagues Dr. Suresh Patel, Dr.
Rajan Jadav in Dept. of Bioscience, Rajkot.
I am highly obliged and express my deep sense of gratitude to my Father - Mr. P.J. Pathak & Mother - Smt. Kusumben Pathak for their constant support and encouragement in all my work.
My special thanks to my elder brother Mr. Kashyap Pathak, who always provided me moral support throughout two years and in early morning in heavy winter during my toughest days of field work.I also thank my younger brother Mayur Pathak for his helping hand and taking care of things when good help was in demand.
I express my gratitude to my sister Prof. Nita Joshi and her daughter Chi. Siniva Joshi for giving me company in my field work and sometimes for taking care of the household during my busy schedule.
Last but not the least, I wish to express my gratitude from the bottom of my heart for my father-in-law Mr. T.B.Shah & mother-in-law
Mrs. Savitaben Shah for always extending their constant support though they are facing many physical odds. I express my deep sense and gratitude to my husband – Mr.
Virendra Shah for his continuous noble moral support.
Lastly, I express my sincere thanks to all other known / unknown persons whom I have come across during my field & thesis work, who have directly or indirectly become instrumental in completing my work.
______
(Chetna Pathak) CONTENTS
INTRODUCTION :-
CHAPTER-1 STUDY AREA 4
CHAPTER-2 POPULATION OF THE
PISCIVOROUS BIRDS 33
CHAPTER-3 HABITAT UTILIZATION BY THE
PISCIVOROUS BIRDS 73
CHAPTER-4 FOOD AND FEEDING HABITS OF
THE PISCIVOROUS BIRDS 120
CHAPTER-5 BREEDING BIOLOGY OF THE
PISCIVOROUS BIRDS 138
SUMMARY 163
REFERENCES 181 CERTIFICATE
This is to certify that the data embodied in this thesis entitled
“ASTUDYOFECOLOGYOFTHEPISCIVOROUSBIRDSAT
THOL BIRD SANCTURY” is an original piece of research work carried out and interpreted by Mrs. Chetna P. Palhak under my guidance.
It is further certified that she has put in more than eleven terms of research work and that this work has not been submitted to any other University/institution for award of Ph.D. degree.
Forwarded through’
Head, Department of Biosciences, Saurashtra University, (Dr.V.C. Soni) Rajkot. Proessor, Department of Biosciences, Saurashtra University, Rajkot. INTRODUCTION
Piscivorous birds are essential ecological components of wetland ecosystem, capable of transporting nutrients in a single season, and because of their numbers and mobility, these birds play an important role in energy movement in the wetlands (Kahl
1964, Kushlan 1976b, 1977 and Christy et al. 1981).
Piscivorous birds occupy a relatively high position in the food of predatory niches (Kushlan 1978b).
In the present study, birds of the families Pelecanidae (Pelicans),
Phalcrocoracidae (Cormorants and Darters), Ardeidae (Herons and Egrets),
Ciconiidae (Stroks), Threskiornithidae (Ibises and Spoonbill), Laridae (Terns) and
Alcedinidae (Kingfishers) have been selected. The piscivorous, according to their feeding habits, are divided into three groups, namely : 1) Swimming Birds : Large cormorant Phalacrocorax carbo, Indian shag Phalacrocorax fuscicollis, little cormorant Phalacrocorax niger, Darter Anhinga rufa and Pelecans (Pelicanus spp.),
2) Wading Birds : Grey Heron Ardea cinerea, Purpul Heron Ardea purpurea, Cattle
Egret Bubulcus ibis, Pond Heron Ardeola grayii, Large Egret Ardea alba, Median
Egret Egretta intermedia, Little Egret Egretta garzetta, Night Heron Nycticorax nycticorax, Painted Stork Mycteria leucocephala, Openbill Stork Anastomus oscitans, White ibis Threskiornis aethiopica and Spoonbill Platalea leucorodia and 3)
Diving Birds : Common Kingfisher Alcedo atthis, Whitebrested kingfisher Halcyon smyrnensis and River Tern Sterna aurantia.
1 A number of publications on the ecological isolation of congeneric sympatric species are available in ornithological literature (Lack 1971, Rowley et al. 1973, Cody
1974, Houston 1976, Nudds 1982, 1983, Poysa 1984, 1986). A few cases of competition among sympatric herons and ibises have already been reported (Carrick
1959, Meyerriecks 1962, Jenni 1969, Kahl 1972, Kushlan 1976 b, Willard 1977,
Custer and Osborn 1978, Thompson 1978, Hoffman 1978).
In India such studies are linked to a few groups of birds such as vultures
(Grubh 1974), Bulbuls (Vijayan 1975), drongos (Vijayan 1984), Aquilla sp. (Prakash
1988) resident ducks (Sridharan 1989) and migratory ducks (Bhupathy 1991). In the present study, an attempt was made to find out the methods of ecological isolation among the fish eating birds. Feeding location, water depth, and feeding behavior among the fish-eating birds were studied in detail. The degree of overlap in the utilization of these resources and the ways in which they minimize competition were also analyzed.
In India, Dave (2002), Sivasubramanian (1992) studied the biology of piscivorous birds. Other information is generalized and scattered (Mukhopadhyay
1980, Johnson and Rao 1988, Nagalingam 1989, Parasharya 1989, Urfi 1989,
Prabhakarachari et al. (1990). However, breeding biology of some of the species have been well studied i.e., Painted Stork by Desai et al. (1971), Pond Heron by Lamba
(1963), Reef Heron by Parashrya (1984) and Cattle Egret by Singh et al. (1988).
Information on food and feeding habits are scattered (Abdulali 1967, Kahl 1971,
1973, Mukherjee 1971, 1975, Pandey 1974, Newton 1986, Johnson 1988,
Sivasubramanian 1988, Grimwood and Brockleshut 1984, Pal and Bala 1989, Johnson
2 et al. 1990, Navroji 1989 and Sivakumar et al. (1990) Status and conservation
(Rahmani 1989 and Rahmani, Narayan and Rosalind 1990, Hancock 1990, Saikia and
Bhattacharya 1990) and general behavior have also been studied (Kahl 1971a, 1972a and 1972b, Sodhi and Khera 1984, Kumar 1981, Mahadevan et al. 1990 and Saxena
1989).
Taxonomy of most of these birds is known (Baker 1928, Whistler 1935, Kahl
1971c, Ali and Repley 1983 and Hancock and Kushlan 1980). Biology of the piscivorous birds has been widely investigated in different parts of the world. Most works concentrate on their feeding behavior and food requirements (Bowmaker 1963,
Junor 1972a, Begg 1973, Whitefield 1978, Whitefield and Balber 1973, 1979a and b,
Cambary 1985, Donnelly and Huster 1986, Arkell 1979). Other ecological aspects of the pisicivorous birds have also been well studied (Kahl 1966, Krebs 1974 and Burger
1978).
OBJECTIVES OF THE STUDY
1. To know the status of various bird species by population assessment,
2. To assess the habitat availability to various groups of birds,
3. To assess the feeding methods adopted by birds to adjust to the environment,
4. To assess breeding requirement and availability of resources in the area,
5. To know the ecological factors like water level, pH, salt contents, aquatic
plants, fishes etc.
3 CHAPTER-1
STUDY AREA CHAPTER – 1
STUDY AREA
The study was conducted in Thol Bird Sanctuary (TS) famous for its wintering congregation of waterfowl migrating from the Palearctic realm.
LOCATION:
TS is located about 25 km northwest of Ahmedabad between 23o 15' to 23o 30'
N. and 72o 30’ to 72 45’ E. It is 22 km away from the town of Kadi and district in
Mehsana.
4 Fig: 1.1 LOCATIONMAP
5 Fig: - 1.2 LOCATION MAP OF THOL SANCTUARY
6 TOPOGRAPHY:
Thol water body has a total area of 699 ha (6.99 sq. km). Its periphery is 5.62 km. It is a manmade wetland spread on west to east line. There is a continuous earthen bund on its western, southern and eastern periphery, which helps in collection of water that flows into it during the monsoon. The wetland has a variable depth over its entire basin. Even in exceptionally good rainfall, the entire water body is not inundated. Less than half of its basin area holds water on a regular basis by
August - September. By November, only a small part along its South - Western periphery holds water.
As water starts drying up from eastern and northern sides, agriculture takes over these dry areas of the water body. There is a continuous ditch located along the Western and Southern bund besides the approach road. This ditch has varying width and depth of 10 to 25 metres and 0.50 to 0.90 metres respectively.
BOUNDARY:
A masonry wall around the border separates the TS from the surrounding agricultural fields.
There are four villages, Bhimasan, Hajipur, Karoli and Jethalaj in the immediate vicinity of the sanctuary.
SOIL:
The soil is of thick alluvium, and on dry grounded in summer.
7 HYDROLOGY:
The catchment area of the waterbody is located to its north and north – east. Water finds its way through a number of canals draining into the feeder canal located on the north - northeastern sides of the water body. Water is received through the following canals at Thol water body (Vaghela 1993),
(1) Eastern canal (2) Saij - Hajipur canal (3) Irana - Indrad - Wamaj Canal (4) Hajipur - Pivaj canal (5)
Eastern feeder at Saghan drain (6) Jaspur canal.
In addition to the feeder canal, the water body receives run-off water directly from the catchment area. Before the feeder canal reaches the manmade wetland, there is a diversion which is known as waste weir and is employed to control the volume of water in the water body. If the level of water reaches beyond 2.75metres the water is diverted to waste weir. Waste weir drains into a canal which runs along the eastern boundary of the Thol pond to reach Nalsarovar Bird Sanctuary located south of TS. TS and Nalsarovar are thus connected with each other.
Thol waterbody supports a well-developed canal based irrigation system. There are four head regulators at the waterbody to control the flow of water. The canals and their distributaries / sub- distributaries are about 19.97 km long. The villages of Thol, Jhaloda, Adhana and Vayana receive water from these canals.
8 Table-1.1: Details of Thol waterbody
Particulars Measure
1. Fill Supply Level (FSL) 49.68m
2. High Flood Level (HFL) 40.90m
3. Top of the bank 52.42m
4. By - Pass Level 50.29m
5. Sill Level 46.63m
6. Catchments area 155.34 sq. km.
7. Storage Capacity 907.37cubic m.
8. Total Command Area 3,37S0 acres
9. Irrigation Command Area 1,835 acres
10. Area of the tank 1,728.31 acres
11. Area under submergence at FSL 1780 acres
9 Table-1.2: Details of irrigation canals of Thol water body
No. Canal No./ Distributory Length (km) Command Discharge
Area (Acres) (cusecs)
1. Canal 2 2.56 360 09.00
2. Canal 3 4.10 435 11.00
3. Canal 4 6.70 300 26.00
4. Distributory 1 of Canal 4 0.80 100 02.80
5. Sub-Distri of Distri 1 0.65 100 02.80
6. Distri 2 of canal 4 2.52 200 10.00
7. Distri 3 of canal 4 2.64 285 12.00
10 CLIMATE:
TS experiences three distinct seasons namely winter (Nov. to Feb.), summer (April to May) and monsoon (June to Sept.). Months of October and March mark the transition period from monsoon to winter and winter to summer respectively. The lake receives rainfall from July to September through the southwest monsoon. Old records for Mehsana district in general (Rajyagor 1975), as well as rainfall data of previous years at TS (Table – 1.6) indicate that the rainfall is highly erratic and ranges from 100 to 900 mm. The overall climate of the area is sub humid to semi arid.
Meteorological variables, rainfall, temperature (maximum and minimum), humidity, photoperiod in hours and evaporation were also recorded.
11 Table-1.3: Monthly Climatic Data Source: (Station name –Gandhinagar, Station
Code: Gandhinagar, Local River / Basin –Sabarmati, Year: 2005)
Month Average Average Relative Rainfall Pan Photoperiod
Min.Temp. Max.Temp. Humidity (mm) Evapo. ( hours)
(oC) (oC) (%)
January 14.7 26.9 56.6 0 90.5 10.55
February 16.8 31.2 45.4 0 96.4 11.25
March 20.9 34.6 50.6 0 125.3 12.04
April 25.1 37.9 46.3 0 181.9 12.47
May 28.5 39.8 52.4 0 210.2 13.14
June 28.3 35.4 65.2 35.5 158.5 13.33
July 26.8 30.9 86.7 230.4 96.5 13.21
August 25.6 29.6 87.6 565.7 62.3 12.55
September 26 31.7 74.4 65.9 92.8 12.17
October 24.4 34.5 62.5 0 102.6 11.36
November 20 32.8 59.2 0 84.4 11.01
December 15.9 28.8 56.1 0 89.1 10.48
12 Fig. 1.3 - Climatic data – 2005
13 Table-1.4: Monthly Climatic Data Source: (Station name –Gandhinagar, Station
Code: Gandhinagar, Local River / Basin –Sabarmati, Year: 2006)
Month Average Average Relative Rainfall Pan Photoperiod
Min.Temp. Max.Temp. Humidity (mm) Evapo. ( hours)
(oC) (oC) (%)
January 14.9 27.1 48 0 92.1 10.55
February 19.5 33.3 47.1 0 95.2 11.23
March 21 33.5 44.2 1.5 104.7 12.02
April 25.1 37.6 43.4 0 153.2 12.46
May 29 40.4 44 0 203.7 13.14
June 28 36.5 64.7 100.5 146.1 13.34
July 26.4 30.8 80 259.9 76.8 13.23
August 25.4 28.6 85.6 554.5 60.6 12.56
September 26.4 32.3 71.5 148.5 95.3 12.18
October 24.7 33.7 63.6 0 105.3 11.35
November 22.5 32.1 61.5 0 89.3 10.58
December 15.5 28.5 55.5 0 90.6 10.47
14 Fig. 1.4 - Climatic data - 2006
15 Table-1.5: Monthly Climatic Data Source: (Station name –Gandhinagar, Station
Code: Gandhinagar, Local River / Basin –Sabarmati, Year: 2007)
Month Average Average Relative Rainfall Pan Photoperiod
Min.Temp. Max.Temp. Humidity (mm) Evapo. (hours)
(oC) (oC) (%)
January 15 26.7 60.6 0 89.7 10.54
February 17.8 29.8 61.4 0 97.3 11.25
March 20.3 33.6 51 0 155.5 12.05
April 25.5 38.7 50.3 0.8 213.3 12.45
May 28 39.2 57.9 3 211.9 13.13
June 29.1 36.7 66.6 61.5 158 13.3
July 26.9 30.8 76.5 647.5 84.5 13.22
August 26.2 30.5 80.9 415 64.8 12.54
September 26.6 32.3 74.4 52.5 92 12.17
October 22.7 33.1 61.3 0 111.1 11.37
November 16.5 32.3 54.1 0 85.6 11
December 15.5 27.6 47.5 0 88.2 10.48
16 Fig. 1.5 - Climatic data – 2007
17 TEMPERATURE:
The lowest monthly average temperature was 14.7 oC in Jan. 2005 while the highest monthly average temperature was 40.4 oC in May 2006. (Table -1.3 & 1.4).
Table-1.6 Yearly average raninfal of Kadi Taluka
Year Rainfall (mm)
1980 644
1981 1032
1982 511
1983 955
1984 709
1985 542
1986 302
1987 207
1988 806
1989 440
1990 946
1991 796
1992 517
1993 785
1994 943
1995 262
1996 403
1997 680
18 1998 756
1999 452
2000 216
2001 623
2002 278
2003 720
2004 636
2005 895
2006 1250
Table-1.7: Average pH (mean) recorded at T.S.
Month pH-2005 pH-2006
January 9.0 9.0
February 9.0 10.0
March 10.0 11.0
April 10.0 11.0
May 12.0 12.0
June 12.0 12.0
July 8.5 8.5
August 8.5 8.5
September 8.5 8.0
October 8.0 8.0
November 7.0 7.0
December 7.5 7.5
19 Fig.-1.7 Average pH (mean) recorded at T.S.
20 Table-1.8: Average total hardness in ppm recorded at T.S.
Month Total Hardness-2005 Total Hardness-2006
January 187.20 203.38
February 194.05 171.35
March 155.15 164.05
April 142.95 140.90
May 157.35 144.42
June 113.20 126.87
July 183.56 230.55
August 236.75 282.13
September 254.59 233.39
October 183.60 208.92
November 204.64 193.00
December 207.33 167.44
21 Fig.-1.8 Average total hardness in ppm recorded at T.S.
22 Table-1.9: Monthly average calcium hardness in ppm recorded at T.S.
Month Ca++ Hardness-2005 Ca++ Hardness-2006
January 124.80 133.70
February 143.70 125.85
March 102.40 107.80
April 87.80 90.10
May 85.90 84.25
June 63.10 72.75
July 108.33 150.35
August 162.52 210.00
September 184.47 190.00
October 142.42 170.75
November 165.50 167.40
December 169.75 152.35
23 Fig-1.9 Monthly average calcium hardness in ppm recorded at T.S.
24 Table-1.10: Monthly average magnesium hardness in ppm
recorded at T.S.
Month Mg++ Hardness-2005 Mg++ Hardness-2006
January 62.40 70.10
February 50.35 45.50
March 52.75 56.25
April 55.18 50.80
May 64.45 60.17
June 50.10 54.12
July 75.23 80.20
August 74.45 72.13
September 70.12 43.39
October 41.18 38.17
November 39.14 25.60
December 37.58 15.09
25 Fig-1.10 Monthly average magnesium hardness in ppm recorded at T.S.
26 Table-1.11: Monthly average chlorinity in ppm recorded at T.S
Month Chlorinity-2005 Chlorinity-2006
January 142 106
February 143 113
March 145 123
April 150 132
May 155 137
June 160 140
July 102 107
August 110 112
September 114 120
October 125 122
November 135 132
December 140 140
27 Fig.-1.11 Monthly average chlorinity in ppm recorded at T.S
WATER – DEPTH:
The highest average depth of water during the study period was in 2005 which occurred in July and was 3.04 meter and lowest water depth was in June 2005 and 2006 and was 0.60 metre. (Table-
1.12).
28 Table-1.12: Monthly average water depth in metres at T.S.
Month 2005 2006
January 1.37 1.67
February 1.21 1.52
March 0.91 1.52
April 0.91 1.37
May 0.79 0.91
June 0.6 0.6
July 2.74 3.04
August 2.59 2.59
September 2.59 2.43
October 2.43 2.13
November 2.13 1.98
December 1.52 1.82
29 Fig.-1.12 Monthly average water depth in metres at T.S.
30 VEGETATION:
The vegetation of the TS can broadly be categorized into two groups:
Aquatic and Terrestrial.
AQUATIC:
A. Submerged rooted vegetation Ceratophyllam demersum and Hydrilla veorticillata.
B. Free floating vegetation Eichhornia crassipes and Algae.
C. Rooted floating vegetation Ipomoea aquatica, Neptunia oleracea.
Terrestrial vegetation of the TS is of scrub type. Acacia nilotica is a dominant tree species which is also found within the pond. There are agricultural fields and the landscape has trees of Acacia nilotica, Prosopis chilensis, P. cineraria, Balanties algytiaca, Salvadora persica and S. oleoides.
Bushes of Zizyphus sp. and those of Capparis deciduas are common.
FLORA:
A check list of the macrophytes (aquatic and terrestrial) recorded at TS is given in Appendix-1.
FAUNA:
The fauna other than birds includes several species of invertebrates and vertebrates. Among the invertebrates, some of protozoa: Volvox sp., Amoeboid forms, coelenterata: Hydra, arthropoda:
Daphnia sp., Cyclops sp., Cypris sp. etc.
Among the vertebrates,
31 FISHES: Channa punctatus, Heleropneustes fossilis, Chela bacaila, Barlous stigma
AMPHIBIANS: Bull frog (Hoplobatrachus tigerinus), Marbled Toad (Bufo stomaticus).
REPTILES:
Rat snake (Ptyas mucosus), Cobra (Naja naja), Garden Lizard (Calotes versicolor), Bengal
Monitor (Varanus bengalensis), Indian Flapshell Turtle (Lissemys punctata).
MAMMALS:
Eight species of mammals have been listed by (Rajyagor 1975) such as Common Langur
(Presbytis entellus), Jungle Cat (Felis chaus), Common Mongoose (Herpestes edwardsi), Jackal
(Canis aureus), Pale Hedgehog (Parachinus micropus), Grey Mask Shrew (Suncus murinus), Indian
Flying fox (Pteropus giganteus) and Nilgai (Boselaphus tragocamelus).
ANTHROPOGENIC INFLUENCES:
Agriculture, industries, fishing, oil drilling, tourism and livestock grazing were found to be the human activities noticed and documented at T.S. Each activity posed some kind of threat to waterfowl and also to human denizens living around T.S. The following threats were identified: non-ecofriendly irrigation practice, use of pesticides and fertilizers, intensification of agriculture, shift towards growing cash crops, proliferation of industries in the catchment area of TS, pollution by hazardous industries, and diversion of agricultural land for industry, oil spills from oil wells, intensive fishing, poaching of birds, littering, noise pollution and disturbance due to livestock movement. Irrigation, pollution by pesticides and industry and intensive fishing by far posed the biggest threats to waterfowl at T.S.
32 CHAPTER-2
POPULATION OF THE
PISCIVOROUS BIRDS CHAPTER – 2
POPULATION OF PISCIVOROUS BIRDS
INTRODUCTION
Population censusing is a methodological problem in ecology, particularly for mobile animals which are distributed over a large area. Most ecological studies of birds use abundance or number of birds per unit area as the basic information on their population. A measure of the relative abundance of most birds is generally easy to obtain because of their relatively large size, conspicuous behaviour, and diurnal habits. An accurate figure on the population of birds, however, is more difficult because birds are highly mobile and have the ability to interact with an observer.
The quality of the wetland can be assessed by monitoring the population of wetland birds.
However, no serious attempt has been made to study the population of wetland birds in our country except the study of reports (Prakash 1988), resident ducks (Sridharan 1989) and migratory ducks
(Bhupathy 1991) of Keoladeo National Park.
METHODOLOGY:
I got an inspiration to prepare the checklist of avifauna from my three years experience of the
Sardar Sarvor Project of the Nal Sarover and my M.Phil. work at Gujarat University, Ahmedabad and
I also join the survey of avifauna conducted by the Forest Department, Gujarat in 2006 at Thol Bird
Sanctuary so , I found it interesting for the census of waterfoul population . Initialy I surveyed three sites of T.S. Site – A : From ONGC well located in the north central part (Vegetative and Puddles).
Site - B: From Jethlaj village (Vegetative and Puddles). Site – C: From front side of watch tower
(Fully open and deep water). Which were different from each other such as loction, concerning area, watertable, water quality, surrounding area, vegetation etc.
33 In the present study population of weatland birds was estimated by direct count method.
(Sivasubramanian 1992). Several other workers have also used this method for various birds. (Weller,
1975; Kand, 1981; Sjoberg, 1981; Shah et. al, 1983; Perinnou, 1987; Prakash, 1988; Sridharn, 1989;
Bhupathy, 1991.)
The survey of three sites of this area was done during January 2005 to December 2006. Counts were carried out from 6:30 a.m to 11:00 a.m 20X50 binocular was used. Every site was being visited monthly. So that the figures for the population census such as means, median and standard deviation, percentage, average etc. can be acquired obtained.
Speices diversity index was calculated using the Shannon-Weiner index “H” formula
(Levins1968):
s 1 HPLP i n i i 1
Where Pi = n1 ------N th (ni = number of i species, N = sum of ni ) s = number of species
The species diversity index was the lowest during Augest (3.17) and highest in February (4.83) during 2005. In 2006 it was the lowest in September (3.73) and highest in January (4.91) repectively
(table-2.5)
RESULTS AND DISCUSSION
Of 23 species of fish eating birds recorded from the sanctuary, 6 species were of swimming birds while 13 species of wading birds and 4 species of diving birds. The highest number recorded was 34 of Rosy Pelican whereas the lowest was that of the Little Blue Kingfisher Population and status of fish eating birds during the study period is summarized in (Table: 2.3 & 2.4.) The fish eating bird’s population fluctulates with water level in T. S. They congregate in large numbers for breeding during monsoon when water depth is higher. During winter (moderate water depth), only resident birds and late breeders stay in the T. S. when water levels receeds during spring and early summer, large expanse of shallow marsh and swamp dry up. This forces the fish to congregate in small pools there by providing a highly concentrated and easily harvestable energy source for fish eating birds. Further, in late summer, most of these pools also dry up forcing the dispersal of the few remaining birds from the sanctuary.
35 TABLE-2.1: Number of species recorded in each month at the three sites with
mean, median and standard deviation
Month Site–A Site–B Site–C
January – 05 18 20 11
February – 05 15 20 11
March – 05 15 18 10
April – 05 12 18 10
May – 05 11 18 10
June – 05 09 17 09
July – 05 11 17 09
August – 05 11 16 09
September – 05 10 10 09
October – 05 11 11 10
November – 05 12 13 11
December – 05 13 15 11
January – 06 14 22 11
February – 06 14 23 11
Mean ` 12.57 17.00 10.14
Median 12.00 17.50 10.00
S. D. 02.41 03.80 00.86
Minimum 09 10 09
Maximum 18 23 11
Site – A : ONGC well located in the north central part (Vegetative and Puddles).
Site – B : From Jethlaj village (Vegetative and Puddles).
Site – C : From front side of watch tower (Fully open and deep water).
36 Fig.-2.1 Number of bird species recorded in each month at three sites
with mean, median and standard deviation
37 Table-2.2: Number of bird species recorded in each month at
three sites with mean, median and standard deviation
Site–A Site–B Site–C January–06 14 22 11 February–06 14 23 11 March–06 16 17 11 April–06 11 17 10 May–06 10 18 11 June–06 10 15 9 July–06 10 17 10 August–06 12 16 9 September–06 11 15 10 October–06 12 12 10 November–06 12 12 13 December–06 13 14 17 January–07 17 23 11 February–07 15 22 11 Mean 12.64 17.35 11 Median 12 17 11 S. D. 2.27 3.81 2 Minimum 10 12 9 Maximum 17 23 11
Site – A : ONGC well located in the north central part (Vegetative and Puddles).
Site – B : From Jethlaj village (Vegetative and Puddles).
Site – C : From front side of watch tower (Fully open and deep water).
38 Fig.-2.2 Number of species recorded in each month at three sites
with mean, median and standard deviation
39 Table–2.3 : Month-wise census of individual Piscivourous birds at T.S. – 2005
No. Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 LargeCormorant 285 280 260 250 200 190 180 280 300 295 293 289
2 IndianShag 317 315 290 272 247 200 250 320 340 330 323 318
3 LittleCormorant 232 228 200 190 175 165 190 225 250 247 239 235
4Darter 8754022361098
5Pelican 15017012035 0 0 0 0 0 0 10 38
6 GreyHeron 50 49 38 35 32 30 30 35 50 58 50 50
7 PurpleHeron 55 52 50 45 42 40 42 45 47 58 58 60
8 PondHeron 37 35 32 31 28 25 20 28 30 34 39 35
9 LargeEgret 55 52 50 48 40 32 28 20 38 68 55 58
10MedianEgret 90 85 80 75 40 32 20 34 102 90 88 89
11 LittleEgret 92 90 85 80 70 67 40 32 58 120 100 95
12 CattleEgret 128 120 87 75 68 55 40 70 120 170 150 135
13PaintedStork 55 57 28 18 12 10 12 28 30 40 52 60
40 14OpenbillStork 32 26 17 12 10 5 0 0 6 32 38 40
15WhiteIbis 87 80 79 60 65 50 55 55 50 100 90 85
16BlackIbis 28 21 20 15 13 12 17 23 25 28 30 29
17GlossyIbis 30 26 36 29 25 24 23 19 21 26 31 31
18 EurasianSpoonbill 485 450 350 300 90 102 150 200 225 500 489 480
19RuddyShelduck 200 120 0 0 0 0 0 0 0 15 120 250
20RiverTern 1012 8 6 5 5 4 3 2 4 5 7
21LittleTern 1215 5 6 5 4 7 3 5 3 2 22
22WhiteBreastedKingfisher 7 5 6 5 5 4 3 5 5 7 5 6
23LittleblueKingfisher 6 7 7 5 5 4 5 6 6 7 6 5
TOTAL : 782 596 465 399 411 434 459 577 774 814 797 751
41 Table–2.4 : Month-wise census of individual piscivourous birds at T.S. – 2006
No. Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 LargeCormorant 300 302 200 190 185 150 180 190 320 321 305 304
2 IndianShag 395 390 385 355 300 290 290 345 400 397 394 396
3 LittleCormorant 270 257 233 180 175 100 185 240 294 280 279 276
4Darter 1011 8 5 1 5 5 6 5121311
5Pelican 250 321 30065 39 0 0 0 0 0 38 120
6 GreyHeron 48 51 32 30 30 31 37 48 50 56 55 53
7 PurpleHeron 59 55 52 50 35 37 40 44 58 58 57 58
8 PondHeron 47 37 32 30 32 19 12 28 52 53 50 42
9 LargeEgret 55 50 47 40 28 30 32 45 62 68 70 62
10 MedianEgret 95 86 70 61 50 35 137 140 135 120 112 100
11 LittleEgret 98 91 76 79 54 57 153 41 62 110 108 102
12 CattleEgret 123 115 104 101 93 75 117 150 150 137 132 130
13 PaintedStork 110 120 100 90 88 82 62 56 78 60 72 122
42 14 OpenbillStork 100 116 91 83 77 60 65 125 119 118 120 122
15WhiteIbis 88 82 76 80 82 65 32 28 57 70 92 90
16BlackIbis 20 5 22 12 10 15 18 17 21 32 3 4
17GlossyIbis 26 24 20 18 15 11 24 22 31 37 29 23
18 EurasianSpoonbill 134 105 137 137 95 80 87 144 148 160 144 140
19RuddyShelduck 300 120 0 0 0 0 0 0 0 20 150 275
20RiverTern 8 2 76 5 40 0 35 4 5
21LittleTern 12 15 8 3 2 1 4 5 4 6 8 10
22WhiteBreastedKingfisher 3 8 4 5 6 5 5 4 6 7 9 8
23Littlebluekingfisher 6 7 5 5 4 3 2 1 2 4 6 7
TOTAL : 864 1040 661 493 449 373 381 414 380 524 854 960
43 POPULATION OF SWIMMING BIRDS
LARGE CORMORANT
Among three sp. of cormorants, the population of a large cormorant was average.
Possibly, they are unable to catch the fish in low water depth and this might explain their low numbers in the Sanctuary. Junor (1972) has noted that White breasted cormorant can dive to a maximum depth of 5.5 m in comparison to only 2.1 m for the Darter.
The fluctuation in the population of the large cormorant showed a similar trend during the study (Tables–2.3 & 2.4). The Large Cormorant extensively used the lake mainly during the breeding season (July to September). They started arriving during July end and the number gradually built and till November, the population remained almost stable. The lowest population was during March to June in all the years. This was related mainly to the water level. Large Cormorant prefers deeper open water for feeding and in summer most of the open water area dried up leaving only puddles available.
INDIAN SHAG
Indian Shag, a breeding migrant was observed in high number during 2006. The low population in 2005 might be due to comparatively low rainfall. Population of Indian
Shag reached a peak in July and remained stable till October. The decline of population started during November and most of them left by February. Dispersal of juveniles and adults occurs at the end of nesting. Dispersal usually occurs from areas where resources are scarce or unavailable to more favorable areas (Byrd 1978). For example, after completing nesting in Florida, birds tend to disperse northward into temperate marshes
44 (Kushlan and Robertsen 1977). The peak (fig.-2.3b) in September - October 2006 was due to the successful hatching.
LITTLE CORMORANT
The Little Cormorant was observed in all the months except May. The highest population was recorded in July - November 2006.
DARTER
Darter was observed in very low population in the sanctuary. The highest population (13 birds) in two years was recorded in November 2006.
PELICANS
Pelicans are winter visitors to the T.S. Pelicans start arriving in the Sanctuary by
November in a year of normal rainfall. The highest population was observed in February
2006.
45 Fig.-2.3a Month-wise census of Large Cormorant at T.S. – 2005, 2006
46 Fig.-2.3b Month-wise census of Indian Shag at T.S. – 2005, 2006
47 Fig.-2.3c Month-wise census of Little Cormorant at T.S. – 2005, 2006
48 Fig.-2.3d Month-wise census of Darter at T.S. – 2005, 2006
49 Fig.-2.3e Month-wise census of Pelican at T.S. – 2005, 2006
50 POPULATION OF WADING BIRDS
Wading birds are conspicuous members of the aquatic avifauna of Thol Bird
Sanctuary. Herons, Egrets, Storks, Ibises and Spoonbill occupy high - levels in the aquatic food chains and appear to be sensitive to disturbance in aquatic ecosystems.
HERONS
The population of four species of herons namely Grey Heron, Purple Heron, Night
Heron and Pond Herons was higher during autumn and winter.
Highest population of Grey heron was in October 2005 (Fig-2.3f). However, all the months except those in summer had approximately 35 individuals in 2005 and 30 in
2006. Maximum of 60 Purple Herons were recorded in December 2006(Fig-2.3g)
The Pond Heron was recorded during all the months during the study. The highest number was recorded in November 2006(Fig-2.3h).
EGRETS
All the egret species except Cattle Egret showed a similar trend in the population.
Large Egret, Median Egret and Little Egret were recorded mostly in breeding seasons.
They were present in almost all the months inside the sanctuary, although in varying numbers (Fig-2.3i, j, k, l).
51 STORKS
The population trend of two species of Storks showed two different patterns as discussed below:
OPENBILL AND PAINTED STORK:
The openbill and painted stork are mainly breeding migrants. Even though openbill stork's number was average in all the months (Fig-2.3m), their peak population was in the end of monsoon and early winter. Poor feeding conditions resulting from a shift in natural hydrologic cycles might have affected stork nesting population in several ways besides reducing nesting success such as causing lack of nest initiation and emigration to other breeding regions. Quality of feeding condition is probably an important cue for population fluctuation in many stork species (Kushlan et al. 1975, Kushlan 1976c, Frederic and
Collopy 1988, Rodgers 1987).
Among the colonial fish eating birds, the Painted Stork is the last to commence breeding inside the sanctuary. The population of the Painted Stork was very high inside the 5sanctuary. The highest population of 122 (Table-2.3) individuals was recorded in
December 2006.
IBIS AND SPOONBILL:
A large number of white Ibis was observed only during the winter. Population was low during summer.
The Spoonbill was recorded thoughout winter and spring in both the years of study (more than 450 birds in October and November 2005). As in the case of white Ibis
52 and Glossy Ibis, this was due to the normal rainfall of the year. Fig.-2.3p shows that the
Indian Black Ibis was very low during its breeding period i.e. from June to October.
Fig.-2.3f Month-wise census of Grey Heron at T.S. – 2005, 2006
53 Fig.-2.3g Month-wise census of Purple Heron at T.S. – 2005, 2006
54 Fig.-2.3h Month-wise census of Pond Heron at T.S. – 2005, 2006
55 Fig.-2.3i Month-wise census of large Egret at T.S. – 2005, 2006
56 Fig.-2.3j Month-wise census of Median Egret at T.S. – 2005, 2006
57 Fig.-2.3k Month-wise census of Little Egret at T.S. – 2005, 2006
58 Fig.-2.3l Month-wise census of Cattle Egret at T.S. – 2005, 2006
59 Fig.-2.3m Month-wise census of Painted Stork at T.S. – 2005, 2006
60 Fig.-2.3n Month-wise census of Openbill Stork at T.S. – 2005, 2006
61 Fig.-2.3o Month-wise census of White Ibis at T.S. – 2005, 2006
62 Fig.-2.3p Month-wise census of Black Ibis at T.S. – 2005, 2006
63 Fig.-2.3q Month-wise census of Glossy Ibis at T.S. – 2005, 2006
64 Fig.-2.3r Month-wise census of Eurasian Spoonbill at T.S. – 2005, 2006
65 Fig.-2.3s Month-wise census of Ruddy Shelduck at T.S. – 2005, 2006
66 DIVING BIRDS
Two species of Kingfisher are included in the diving birds. They constituted only
1.5 % of the total population of fish eating birds. River Tern and Little tern are also included in the diving birds group. Terns contributed more than 60% of the total population of diving birds. A maximum of Little Terns (22) was recorded in December
2005. In November 2006, the lake had higher number (9) of common Kingfisher.
The population of Piscivorous birds have long been a focus for conservation action, particularly for efforts to preserve the wetlands on which they depend. They are worthy of such attention not only for aesthetic value but also as useful indicators of the ecological health of these ecosystems.
Fig.-2.3t Month-wise census of River Tern at T.S. – 2005, 2006
67 Fig.-2.3u Month-wise census of Little Tern at T.S. – 2005, 2006
68 Fig.-2.3v Month-wise census of White Breasted Kingfisher at
T.S. – 2005, 2006
69 Fig.-2.3w Month-wise census of Little Blue Kingfisher at
T.S. – 2005, 2006
70 Table-2.5 Shannon-weiner species diversity Index of the Piscivorous
Birds during various months 2005 - 2006
MONTHS YEAR 2005 YEAR 2006
JANUARY 4.60 4.91 HIGHEST
FEBRUARY 4.83 HIGHEST 4.15
MARCH 4.35 4.44
APRIL 4.13 4.59
MAY 3.95 4.43
JUNE 3.78 4.14
JULY 3.25 3.91
AUGUST 3.17 LOWEST 4.03
SEPTEMBER 3.53 3.73 LOWEST
OCTOBER 3.87 4.56
NOVEMBER 4.23 4.45
DECEMBER 4.57 4.43
71 Fig.-2.5 Shannon-weiner species diversity Index of the Piscivorous birds
during various months – 2005-2006
6.0 5.0 4.0 YEAR 2005 3.0 YEAR 2006 2.0 1.0 0.0
Y H Y Y R R R A L E E A C U R M J B B U A M M N M E E A T V J P O E N S
72 CHAPTER-3
HABITAT UTILIZATION BY THE
PISCIVOROUS BIRDS CHAPTER – 3
HABITAT UTILIZATION BY THE PISCIVOROUS BIRDS
INTRODUCTION
Study on the field characteristics, status, distribution and notes on the general ecology of most of the Indian birds are available (Baker 1922-32, 1932-35; Whistler and
(1935), Ali and Ripley 1983, Bhupathy 1985, Jayaraman 1985). However, specific information on the habitat requirement of most of the birds are lacking in the country.
Kahl (1972a, 1972b) descrided the feeding seasonality, food consumption and feeding behavior in different habitats for some species of storks. Kent (1986, 1987) reported the effects of varying behavior, foraging efficiency of egrets in different habitats.
Feeding habitats of nesting, spatial use, social influence, foraging divisions, patch use and seasonality of wading birds in different habitats are described by Erwin (1981-1985).
Habitat generally refers to the place where each kind of organism is normally found. In other words it refers to the place where the animal lives. And such an assessment of specific habitat requirement of individual species is vital for the management of a species. Learning the habitat is one of the foremost steps in studying an organism (Odum
1971). Lack (1967) summarized that the birds recognize their ancestral habitat by conspicuous though not necessary features. Habitat association of land bird species have been assessed mainly by using foliage measurements, such as volume of foliage height diversity (MacArthur et al. 1967).
73 Custer and Osborn (1978) studied the feeding habitat use of colonially-breeding herons, egrets and ibises in North Carolina. Kushlan (1976c) described the feeding and habitat preference of the White Ibis in Southern Florida. Meyerriecks (1962) and Kushlan
(1976b) found that longer - legged herons feed in deeper water than shorter- legged ones.
Rodgers (1983) described the foraging methods of herons in different habitat in Florida.
Food of the Night Heron and Little Egret in different habitat has been studied by Fasola
(1981). Fasola (1986) reported the resource use of foraging herons in Agricultural and non-agricultural habitats in Italy. Kushlan et al. (1985), studied the foraging niche relations of wading birds in tropical wet Savannas. Habitat use of Herons and Egrets in
North America is documented by Recher and Recher (1980) Prey consumption of wood storks in different habitats was reported in Everglades National Park (Ogden et al. 1978).
Cooper (1985a), Hafner and Brittons (1983), Hafner (1982), Kushlan and Kushlan (1977),
Kushlan (1981), Mock and Mock (1980).
Habitat use by bird species at TS was recorded on each visit. These categories were
- open water, puddles and peripheral region. The activities were categorized as foraging, resting, roosting and breeding. Open water habitat over other categories was used highly by waterfowl like all ducks, storks, herons, egrets, spoonbills, ibises and many waders.
Use of edge and puddles by nearly half the species was in accordance with a high diversity of small waders at TS, which used this habitat extensively for foraging and roosting. Out of 77 sp. listed (Thol Report – 2002), majority of species used TS for foraging and resting
(82 % and 75 %) In contrast, only 56 % species used it for roosting. There were some species like egrets, spoonbills, cormorants with confirmed breeding record of T. S.
74 METHODOLOGY:
The study of habitat utilization of wetland birds was done; simultaneously the study of population dynamics and breeding biology was also performed. Total 6 habitats were classified; among these most of the habitats used by wetland birds were observed during the study period. Regular habitat surveys were conducted by walking and recording the number of individuals and the habitat in which they were sited. This study was done continuously for two years. At different sites, different species were also recorded from time to time to study a general preference of a specific water body. Birds were observed from 40-50 m distance by using 20 × 50 binoculars walking slowly 300 to
400 hrs.
The preference for a particular habitat by different species and utilization of each habitat by them were studied. Habitats were classified into the following 6 types according to the dominant plant community and water regime.
(1) OPEN WATER
This site is fully open and has deep water. Birds can be observed from the bank as entry in the lake is not allowed. The observation was done early in the morning, at the afternoon and in the evening through binocular and telescopy from the watchtower.
This covers comparatively deeper area of the lake spread over on either side of the dykes and towards the middle of the aquatic blocks with submerged vegetation. This area is the front-side of the lake in the open water area beyond 2 meters from the edge of the pond. Dominant submerged vegetations are Ceratophyllum demersum and Hydrilla veorticillata, free floating vegetation Eichhornia crassipes and rooted floating vegetations
75 are Ipomoea aquatica, Neptunia oleracea. This serves as the chief attraction for all swimming birds. This habitat was used highly by all ducks storks, herons, egrets, spoonbills, ibises and many waders probably due to the presence of a roosting tree in the water area.
(2) SHALLOW WATER WITH SPARSE VEGETATION
This site is located on both the sides of the pathway while entering the sanctuary.
While walking along the path wader birds could be observed here. Apart from this such site is also located near Jethlaj villege.
At the edge, the water level is much less and irregularly distributed amongst the patches of grass and open water is areas with sparse vegetation which usually are covered by a film of water. In this habitat, the vegetation is neither very low, nor is the water volume very open. Ipomoea aquatica forms the major vegetation in these areas. Shallow water with sparse vegetation attracts Ciconidae family sp.and several wading birds could be seen.
(3) GRASS PATCH
This site is located on north central side where cultivation of Acacia is there below which grass patches can be seen. Here wading birds could be observed mostly while walking along the path.
In this type of habitat, the grass grows very thick and forms a kind of mat. This comes up during the monsoon and spring when the grasses are at their peak of vegetative
76 growth. In winter, however, decomposition of grass makes these areas less prominent and attracts several waterfowl species.
(4) IPOMOEA + GRASS
This site is also seen both the sides of the sanctuary, mostly camp side. The observation was done mostly in the morning and in the evening while walking and here
Ardeidae family sp. could be seen.
It is a mixture of Ipomoea sp. and grass. At certain places Eleocharis sp. patches are also included. Mostly to be seen in the area of transition between grass and Ipomoea patches.
(5) TREES AND BRANCHES HANGING OVER WATER
(CULTIVATION AREA)
This site is situated near Jethlaj village. Where entire area is covered with Acacia nilotica trees which could be observed while walking and used binocular.
Tress mainly on the edge of the dyke forms the resting habitat for many birds. The entire aquatic area of the sanctuary is intersected with a number of Acacia nilotica planted on dykes. On either side of these dykes, apart from the clumps of Acacia sp., Salvadora sp., Butea sp., Cassia sp., Prosopis sp., Madhuca sp. and Manilkara sp., other bushes are also noticed. This serves as the chief attraction for many diving birds and these trees serve as nesting sites for various aquatic birds.
77 (6) PUDDLES
This site is located on the front side of the watchtower and the other site is scattered from North side of the sanctuary which could be observed while walking and used binocular.
The water level drops during the dry season (May - June), leaving only a few pools in the deeper areas. Aquatic organisms are concentrated in these increasingly smaller areas and become readily utilizable food for highly mobile predators, particularly wading birds.
78 Plate: 3.1
Roosting of the swimming birds
1) A large group of Pelicans and 2) A large group of Cormorants
79 Plate: 3.2
1) Eurasian Spoonbill – as a wader, with sparse vegetation
2) Black-Crowned Night- Heron roosting on the tree
80 Plate: 3.3
1) Roosting time: Black-Crowned Night Heron on the Accasia nilotica
tree.
2) Purple Heron foage using Stand and Wait method in shallow water
with sparse vegetation
81 Plate: 3.4
1) Immature black-Crowned Night Heron forages by walking
through shallow water with sparse vegetation.
2) Indian Pond Heron forages by a type of Stand and Wait method.
82 Plate: 3.5
Diving Birds
1) At the edge of a mound - Little Blue Kingfisher
2) River Tern at its roosting site.
83 Table-3.1 Percentage frequency of Wading birds (Ardeidae) recorded
in various habitats
No. Habitat Grey Purple Pond Cattle Median Little Large Night Total
Heron Heron Heron Egret Egret Egret Egret Heron
1. Open Water 4 5 2 0 5 6 7 6 35
2. Shallow 15 12 10 7 25 12 15 5 101
water +
Sparce
vegetation
3. Grassy patch 7 18 3 5 10 6 3 0 45
4. Grass + 10 11 12 2 9 4 8 0 56
Ipomoea
5. Trees and 7 7 6 21 6 7 7 28 89
branch over
water
6. Puddles 3 1 2 6 2 1 2 0 17
7. Total 2388 3211 4217 2120 4258 3310 3720 1017 -
observations
84 Fig.-3.1
Percentage frequency of wading birds recorded in various habitats 30
25
20 ) % ( e g a t 15 n e c r e P 10
5
0 Grey Heron Purple Heron Pond Heron Cattle Egret Median Egret Little Egret Large Egret Night Heron
Open Water Shallow w ater + Sparse vegetation Grassy patch Grass + Ipomoea Trees and branch over w ater Puddles
85 Table-3.2 Percentage frequency of Wading birds (Ciconiidae)
recorded in various habitats
No. Habitat Painted Openbill White Glossy Spoonbill Total
Stork Stork Ibis Ibis
1. Open Water 4 0 3 0 12 19
2. Shallow water + 12 2 15 10 35 74
Sparce vegetation
3. Grassy patch 5 1 10 07 0 23
4. Grass + Ipomoea 4 1 8 5 10 28
5. Trees and branch 20 4 18 7 12 61
over water
6. Puddles 2 3 2 2 1 10
7. Total observations 2530 760 3578 2722 4329 -
86 Fig.-3.2
Percentage frequency of wading birds recorded in various habitats 40
35
30 )
% 25 ( e g a t 20 n e c r e 15 P
10
5
0 Painted Stork Openbill Stork White Ibis Glossy Ibis Spoonbill
Open Water Shallow w ater + Sparse vegetation Grassy patch Grass + Ipomoea Trees and branch over w ater Puddles
87 Table-3.3 Percentage frequency of Swimming birds recorded in
various habitats
Large Indian Little No. Habitat Darter Pelicans Cormorant Shag Cormorant
1. Open Water 35 38 40 7 70
Shallow water +
2. Sparse vegetation 20 22 25 2 0
3. Grassy patch 2 3 2 1 0
4. Grass + Ipomoea 3 4 4 1 0
Trees and branch
5. over water 5 4 2 1 3
6. Puddles 8 6 7 1 2
7. Total observation 2720 2350 2620 1240 600
88 Fig.-3.3
Percentage frequency of Swimming Birds recorded in various habitats 80
70
60 )
% 50 ( e g a t 40 n e c r e 30 P
20
10
0 Large Cormorant Indian Shag Little Cormorant Darter Pelicans
Open Water Shallow w ater + Sparse vegetation Grassy patch Grass + Ipomoea Trees and branch over w ater Puddles
89 Table-3.4 Percentage frequency of Diving birds recorded in various habitats
White breasted Little Blue River Little No. Habitat Kingfisher Kingfisher Tern Tern
1. Open Water 5 4 7 3
Shallow water + Sparse
2. vegetation 7 6 0 0
3. Grassy patch 0 0 0 0
4. Grass + Ipomoea 2 3 1 0
5. Trees and branch over water 3 4 1 0
6. Puddles 6 4 1 0
7. Total observation 2503 2304 1891 1087
90 Fig.-3.4
Percentage frequency of Diving Birds recorded in various habitats 8
7
6 )
% 5 (
e g a
t 4 n e c r e 3 P
2
1
0 White breasted Kingfisher Little Blue Kingfisher River Tern Little Tern
Open Water Shallow w ater + Sparse vegetation Grassy patch Grass + Ipomoea Trees and branch over w ater Puddles
RESULTS AND DISCUSSION
A total of 06 habitat types were considered of which two, namely tree and branch over water and grass mound were purely nesting habitats. Hence, only the remaining 04 habitats were utilized for feeding by the Piscivorous birds.
SWIMMING BIRDS
Among 06 habitat types, Cormorants used the open water habitat and puddles for both feeding and non-feeding activities. Six habitats were used for feeding while only two habitats namely edge of the dykes trees and branch over water and cultivation area and grassy patch with sparse vegetation were used for nesting. All species of cormorants preferred open water + sparse vegetation for feeding. Darter used 3 habitats for feeding
91 and only one habitat namely trees and branch over water for roosting. Among feeding habitats, the highest number of birds like Pelicans were observed in open water. The preference of open water for feeding is mainly due to the feeding behavior of diving birds.
WADING BIRDS
Herons & Egrets
Except the Night-Heron, all the other herons used all habitats for feeding and non feeding activities (Table – 3.1). The Night Heron used mostly used three habitats. The highest used habitat was Trees and branch over water. The highest used habitat was shallow water with sparse vegetation for the Grey Heron, Purple Heron, Pond Heron and all types of Egrets. Second preferred habitat was Grassy patch and Grass + Ipomoea. The highest preference of this habitat reflects the feeding behavior of these species. The Grey,
Purple Herons and Large Egret are long-legged birds and hence capable of wading through the shallow water and feed. Whereas, the Pond Heron and Night Heron, as they are short legged birds, prefer to wait at the edge of the water and strike when the prey appears.
Thus, the Grey and Purple Heron preferred shallow water + sparse vegetation and Night
Heron and Pond Heron did so mainly on the edge of the dykes for feeding.
STORKS
The open water habitat mostly was never used by openbill stork whereas both the storks used all the habitats for feeding. Trees and branch over water were used in nesting.
During monsoon, they fed in the puddles available in land area and during summer, they
92 utilized the puddles available in the drying aquatic area. In winter, they used shallow water
+ sparse vegetation and grassy patch habitat for feeding.
IBIS AND SPOONBILL
Large number of white Ibis feed in various microhabitats such as shallow water + sparse vegetation, grass patch and grass + Ipomoea. The highest numbers of spoonbill were in shallow water + sparse vegetation. Large numbers of birds were observed in reed, open water and edge of the habitat (Table-3.2). The selection of habitat for feeding reflects the feeding behavior of each species. The spoonbill was seen to feed in shallow water with sparse vegetation and edge of the dyke, their nesting site was upon trees and branches hanging over water and in cultivation area.
DIVING BIRDS
Diving birds include two species of kingfishers, namely the common kingfisher and white breasted kingfisher and two species of terns. River Tern and Little Tern. The common kingfisher preferred shallow water + sparse vegetation and white breasted kingfisher, the reed. The terns are large birds as compared to the kingfisher and hence their highly preferred habitat was open deep water for feeding. The white breasted kingfisher utilized mostly reed as feeding perch.
SEASONALITY OF FORAGING HABITAT
As the summer advances, water in the wetland area recedes fast into comparatively deeper area and along with the water the aquatic organisms including fish also move into these pools and puddles. As a result, these pools and puddles become teemed with fish attracting a large number of herons, ibises and storks. When the rainy season begins in the
93 Thol Lake, remnant fish stocks move out of pools and puddles by surface water that rises throughout the marsh system. As the fry enter the park along with the water, the waders have a feast, picking up the tiny fry from the shallow areas. Later when the water level rises and before the vegetation gets established (to provide perch for the birds), many of the herons catch the fish by hawking (Sivasubramaniam 1988). Such seasonality of foraging habitat in wading birds was reported earlier by Kushlan (1976b) and Willard
(1977). Seasonal variation in the habitat use of the Piscivorous birds have been given in the Fig.-3.5.
94 Table-3.5 SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
O. SW. G. GR. TR. O. SW. G. GR. TR. O. SW. G. GR. TR. No Name WA SVG PAT IP BOW PUD WA SVG PAT IP BOW PUD WA SVG PAT IP BOW PUD
Large
1. Cormorant 35 25 5 9 11 15 25 30 6 10 10 19 45 20 5 10 15
Indian
2. Shag 50 22 3 3 15 7 40 10 5 3 35 7 50 10 3 3 30 4
Little
3. Cormorant 30 20 7 10 30 3 45 25 5 5 20 0 30 20 3 4 40 3
4. Darter 38 25 3 2 27 5 40 35 0 0 25 0 45 25 0 0 30 0
5. Pelican 90 0 5 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Grey
6. Heron 5 30 20 20 7 18 8 20 22 25 10 15 5 25 21 23 10 15
95 Purple
7. Heron 2 28 20 20 10 20 8 25 23 22 12 10 0 35 21 24 5 15
Pond
8. Heron 2 25 20 20 10 23 4 27 23 25 6 15 1 22 23 21 13 20
Large
9. Egret 20 15 17 13 18 17 25 15 12 10 10 28 15 22 23 27 9 4
Median
10. Egret 5 25 18 22 8 12 5 22 15 15 28 15 5 18 28 22 9 18
Little
11. Egret 18 22 15 15 10 20 15 10 3 2 15 35 8 22 18 12 17 23
96 O. SW. G. GR. TR. O. SW. G. GR. TR. O. SW. G. GR. TR. No. Name PUD PUD PUD WA SVG PAT IP BOW WA SVG PAT IP BOW WA SVG PAT IP BOW
12. Cattle Egret 0 20 28 22 18 12 0 25 28 13 22 12 0 24 2 22 28 3
Painted
13. Stork 10 25 12 13 25 15 18 14 5 5 28 30 8 20 8 4 45 15
14. White Ibis 20 25 15 15 10 15 22 25 12 17 12 22 8 12 16 14 35 15
15. Glossy Ibis 5 35 20 22 25 13 10 30 10 10 25 15 3 35 10 12 15 10
Eurasian
16. Spoonbill 10 30 10 10 20 20 15 35 10 10 15 15 5 30 10 15 25 15
Ruddy
17. Shelduck 85 10 0 0 0 5 0 0 0 0 0 0 0 0 0 0 0 0
18. River Tern 95 0 0 0 0 5 95 0 0 0 0 5 95 0 0 0 0 5
19. Little Tern 90 0 0 0 0 10 0 0 0 0 0 0 0 0 0 0 0 0
97 White
breasted
20. Kingfisher 25 20 0 0 45 10 30 15 0 0 30 25 35 25 0 0 25 15
Common
21. Kingfisher 15 35 0 0 30 20 10 40 0 0 40 10 10 35 0 0 35 20
1. O. WA = OPEN WATER
2. SW. SVG = SHALLOW WATER + SPARSE VEGETATION
3. G. PAT = GRASSY PATCH
4. GR. IP = GRASS + IPOMOEA
5. TR. BOW = TREES AND BRANCH OVER WATER
6. P.U.D. = PUDDLES
98 Fig-3.5a SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
LARGE CORMORANT
WINTER SUMMER MONSOON
PUD PUD PUD 15% 5% 19% O.WA TR.BOW 25% 15% O.WA TR.BOW 35% 11% TR.BOW O.WA 10% GR.IP 45% 10% GR.IP 9% G.PAT GR.IP 5% G.PAT 10% 5% SW.SVG SW.SVG SW.SVG G.PAT 20% 30%
99 Fig-3.5b SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
INDIAN SHAG
WINTER SUMMER MONSOON
PUD PUD 7% PUD TR.BOW 7% 4% 15% O.WA 40% TR.BOW TR.BOW 30% GR.IP 35% O.WA 3% O.WA 50% 50% G.PAT 3% GR.IP 3% GR.IP G.PAT 3% G.PAT SW.SVG SW.SVG SW.SVG 3% 5% 10% 10% 22%
100 Fig-3.5c SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
LITTLE CORMORANT
WINTER SUMMER MONSOON
PUD PUD 3% TR.BOW 3% O.WA 20% O.WA TR.BOW 30% 30% 30%
GR.IP TR.BOW O.WA 5% 40% 45% c G.PAT 5%
GR.IP SW.SVG SW.SVG GR.IP 20% 10% G.PAT G.PAT 20% SW.SVG 4% 7% 25% 3%
101 Fig-3.5d SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
DARTER
WINTER SUMMER MONSOON
PUD 5% TR.BOW TR.BOW 25% 30% TR.BOW O.WA O.WA 27% 38% O.WA 40% 45%
c
GR.IP 2%
G.PAT 3% SW.SVG SW.SVG SW.SVG 35% 25% 25%
102 Fig-3.5e SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
PELICAN
WINTER
G.PAT GR.IP 5% 5%
O.WA 90%
103 Fig-3.5f SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
GREY HERON
WINER SUMMER MONSOON
O.WA O.WA 5% PUD O.WA 8% PUD PUD 15% 5% 18% 15%
SW.SVG SW.SVG TR.BOW TR.BOW 30% 20% TR.BOW 7% 10% 10% SW.SVG c 26%
GR.IP 20% GR.IP GR.IP G.PAT G.PAT 25% 23% G.PAT 22% 20% 21%
104 Fig-3.5g SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
PURPLE HERON
WINTER SUMMER MONSOON
O.WA 2% PUD O.WA O.WA 10% 8% PUD PUD 0% SW.SVG 15% 20% 28% TR.BOW 12% TR.BOW 5% SW.SVG SW.SVG TR.BOW 25% 10% c 35%
GR.IP GR.IP 24% 22% GR.IP G.PAT 20% 20% G.PAT G.PAT 23% 21%
105 Fig-3.5h SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
POND HERON
WINTER SUMMER MONSOON
O.WA O.WA 2% O.WA PUD 4% PUD 1% SW.SVG 15% PUD 20% 25% 23% SW.SVG TR.BOW SW.SVG 22% 6% 27%
c TR.BOW TR.BOW 10% 13%
GR.IP G.PAT 25% G.PAT 20% 23% GR.IP G.PAT GR.IP 20% 23% 21%
106 Fig-3.5i SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
LARGE EGRET
WINTER SUMMER MONSOON
PUD O.WA O.WA TR.BOW O.WA PUD 25% 4% 9% 15% PUD 20% 28% 17%
GR.IP TR.BOW 27% c SW.SVG 18% 15% TR.BOW SW.SVG SW.SVG 10% 15% 22%
GR.IP GR.IP G.PAT G.PAT 10% G.PAT 13% 12% 17% 23%
107 Fig-3.5j SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
INTERMEDIATE MEDIAN EGRET
WINTER SUMMER MONSOON
O.WA O.WA O.WA PUD 5% PUD 5% 6% 15% PUD 18% 13% SW.SVG TR.BOW SW.SVG SW.SVG 22% 9% 18% 28% TR.BOW 9% c TR.BOW 28% G.PAT GR.IP GR.IP 15% 24% 22% G.PAT GR.IP G.PAT 20% 15% 28%
108 Fig-3.5k SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
LITTLE EGRET
WINTER SUMMER MONSOON
O.WA O.WA 18% O.WA 8% 18% PUD PUD 23% 20%
PUD 43% SW.SVG SW.SVG TR.BOW 22% 13% 10% c SW.SVG G.PAT 22% TR.BOW 4% 17% GR.IP GR.IP 3% 15% TR.BOW GR.IP G.PAT 19% 12% G.PAT 15% 18%
109 Fig-3.5l SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
CATTLE EGRET
WINTER SUMMER MONSOON
PUD SW.SVG PUD 4% PUD 20% 12% 12% SW.SVG 25%
TR.BOW SW.SVG TR.BOW 18% 30% TR.BOW 35% c 22%
G.PAT G.PAT 28% 3% GR.IP G.PAT GR.IP GR.IP 22% 28% 13% 28%
110 Fig-3.5m SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
PAINTED STORK
WINTER SUMMER MONSOON
O.WA O.WA PUD 10% 8% PUD O.WA 15% 15% 18% PUD 30%
SW.SVG SW.SVG 25% 20% c TR.BOW SW.SVG 25% 14%
G.PAT G.PAT 8% 5% TR.BOW G.PAT GR.IP 45% GR.IP GR.IP 12% TR.BOW 5% 4% 13% 28%
111 Fig-3.5n SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
WHITE IBIS
WINTER SUMMER MONSOON
O.WA O.WA PUD PUD PUD O.WA 8% 20% 15% 15% 20% 20%
TR.BOW SW.SVG 10% 12%
TR.BOW c 11%
G.PAT GR.IP SW.SVG SW.SVG TR.BOW 16% 15% 25% 23% 35% GR.IP 15% GR.IP G.PAT G.PAT 14% 15% 11%
112 Fig-3.5o SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
GLOSSY IBIS
WINTER SUMMER MONSOON
O.WA O.WA PUD O.WA 4% 10% PUD PUD 15% 4% 12% 11%
SW.SVG 29% TR.BOW TR.BOW 21% 18% SW.SVG c TR.BOW 30% 25% SW.SVG 40% GR.IP 14%
GR.IP G.PAT GR.IP G.PAT G.PAT 18% 17% 10% 10% 12%
113 Fig-3.5p SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
EURASIAN SPOONBILL
WINTER SUMMER MONSOON
O.WA O.WA PUD 5% 10% PUD O.WA 15% 15% 15% PUD 20%
TR.BOW SW.SVG SW.SVG 15% 30% c 30% TR.BOW 25% TR.BOW 20% SW.SVG GR.IP 35% 10% G.PAT GR.IP G.PAT GR.IP 10% G.PAT 10% 10% 15% 10%
114 Fig-3.5q SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
RUDDY SHELDUCK
WINTER
PUD 5% SW.SVG 10%
O.WA 85%
115 Fig-3.5r SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
RIVER TERN
SUMMER MONSOON WINTER
PUD PUD PUD 5% 5% 5%
O.WA 95% O.WA O.WA 95% 95%
116 Fig-3.5s SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
LITTLE TERN
WINTER
PUD 10%
O.WA 90%
117 Fig-3.5t SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
WHITE BREASTED KINGFISHER
WINTER SUMMER MONSOON
PUD 15% PUD PUD O.WA 25% O.WA 10% 25% 30% O.WA 35%
TR.BOW 25%
TR.BOW 45% SW.SVG 20% SW.SVG TR.BOW SW.SVG 15% 30% 25%
118 Fig-3.5u SEASONAL VARIATION IN THE HABITAT UTILIZATION OF PISCIVOROUS BIRDS
COMMON KINGFISHER
WINTER SUMMER MONSOON
O.WA PUD O.WA 15% O.WA 10% 10% PUD 10% PUD 20% 20%
TR.BOW SW.SVG 40% SW.SVG SW.SVG 35% 40% TR.BOW 35% 30% TR.BOW 35%
119 CHAPTER – 4
FOOD AND FEEDING HABITS OF
THE PISCIVOROUS BIRDS
INTRODUCTION:
The ways in which animals partition the available resources have aroused considerable interest, particularly in efforts aimed at demonstrating the competitive exclusion principle or at determining the limiting similarity of coexistence (Cole 1960,
Hardin 1960, MacArthur and Levins 1967, Miller 1967, Lack 1971, May and MacArthur
1972, Cody 1974, Pianka 1974, 1975). These studies examined food as the limiting resource by measuring prey size, bill size, foraging behaviour and prey availability. The emphasis on food as the limiting resource seems partly historical in that Elton (1927) developed his conceptual frame work of niche in terms of the feeding behaviour and food requirement of species.
Several studies on piscivorous birds have touched upon some of these considerations and have generally shown that congeneric piscivorous birds differ by their size, behaviour, feeding sites or food (Carrick 1959, Meyerriecks 1962, Jenni 1969, Kahl
1971a, Kushlan 1976b, Willard 1977, Custer and Osborn 1978, Thompson 1978, Hoffman
1978, Recher and Recher 1980 and Kent 1986).
The conservation and management of piscivorous birds throughout their range have evoked considerable interest and concern (Cambray 1985). Their relatively high
120 energy demand and locally large population make them important components of aquatic ecosystems. Inter-specific differences in size, habitat use, sociality, distribution, responses to seasonal environmental pressure and food habits. Resource partitioning studies analyse how inter-specific competition limits the number of coexisting species. Competition, here defined as the simultaneous demand by two or more organisms of different species for such limited resources as food or space (Koplin and Hoffman 1968) has been studied by both, observing and describing systems and by perturbing and then observing the systems.
Predation by piscivorous birds is one of the forces determining the functional characteristic of this system by existing control pathways of energy flow. The tactical aspects of predation, such as relationship between prey availability and prey consumption and between defensibility and territory size function in determining the nature of the fish to piscivorous birds energy flow. Similar relationship should exist in other feeding habitats that taken together determine the regional pattern of habitat use, prey consumption and the way piscivorous birds meet daily and seasonal food requirements.
More literature on feeding ecology of piscivorous birds in various countries is known qualitatively and in some cases quantitatively. The motor patterns associated with capturing, handling and swallowing prey have been summarized by various authors
(Meyerriecks 1962, Pringle 1964, Cunnigham 1965, Kahl 1964, Blaker 1969a, Carpenter
1971, Dennis 1971, Vestjens 1973, Snow 1975, Kushlan 1978b, Whitefield and Blaber
1978a, 1978b, Mock and Mock 1980, Moser 1986, and Forber 1989).
121 Piscivorous birds have been described in exhaustive literature describing their foraging ecology and food habits. In India, very little information is available at present on the food and feeding habits of the piscivorous birds (Abdulali 1967, Kahl 1971a, 1973,
Mukherjee 1971, 1975, Pandey 1975, Newton 1986, Johnson 1988, Ginwood and
Brockleshut 1984, Pal and Bala 1989, Johnson et al. 1990, Navroj 1990, Sivakumar et al.
1990).
Morphological adaptations for feeding have been reported (Hartman 1961, Huxly
1962, Humphrey and Parkes 1963, Kahl 1965, Duble and Mansuri 1969, Vanden Berge
1970, Payne and Ridey 1976, Recher and Recher 1980). Territorial foraging of piscivorous birds have been reported by Meyerriecks (1962), Hedeen (1967), Recher and Recher
(1972), Snow (1975), Woolfenden et al. (1976), Mock and Mock (1980).
Foraging sociality of piscivorous birds has been described (Woolfenden et al.
1976, Kushlan 1978a, 1978b, Ruseell 1978, Blaker 1969a, 1971, Willard 1977, Whitefield and Blaber 1978, Forber and Simpson 1982, Praulans and Versam 1985, Hafner 1982,
Erwin 1983, Scoh 1984). Food consumption of the adult and juvenile piscivorous birds was well documented by various authors (Siegfried 1972, Kushlan and Kushlan 1977,
Ogdan et al. 1978, Whitefield and Blaber 1978a, 1978b, Kushlan 1979a, Junor 1972,
Draulans 1988).
Food requirements of the piscivorous birds have been extensively studied (Owen
1960, Kahl 1964, Kral and Figala 1966, Vaspemeanu 1968, Dusi and Dusi 1970, Kushlan
1977). More literature on seasonality of prey consumption of piscivorous birds is available elsewhere (Carrick 1962, Kahl 1964, 1966, 1971b, Carroll 1967, Lowemc Connell 1967,
122 Klug and Boswell 1970, Siegfied 1972a, 1972b, Vermon 1971, Urban 1974, Ogden et al.
1978, and Kushlan 1978b, 1986).
The environmental determination of food dispersion is complex, but is critical for understanding the feeding ecology of wading birds. Very few people have studied this aspect (Owen 1957, Kahl 1964, Vespermeanu 1968, Kushlan et al. 1975, Kushlan 1976b,
Ogden et al. 1978). Prey selection of the piscivorous birds was worked out by various authors (Siegfried 1972b, Kushlan and Kushlan 1977, Owen 1955, Kahl 1964, Willard
1977, Jackson 1984, Whitefield and Blaber 1978a, b; Kushlan 1979a, Mock and Mock
1980, Fasola 1981, Rodger Jr. 1976). Information on the feeding depth of the piscivorous birds are incidental and general (Jenni 1969, Willard 1977, Recher and Recher 1980,
Whitefield and Blaker 1978a, b,; Forber and Simpson 1982).
METHODOLOGY:
As the present study was conducted at lake, puddles, sewage, canal and some of human interference was very common. Only direct observation method was applied.
Generally observation was confined to birds within a distance of 40 to 50 m and individuals selected as they were encountered. Where I had a choice of two or more individuals of a species, I chose the nearest one. Observations continued until the bird moved out of the scope for easy identification of prey.
Monthly observations were taken from 13to14 hrs. For accuracy 20 x 50 binocular was used. Timing for different feeding techniques adopted by different birds was recorded by stopwatch.
123 Table– 4.1 Average length of bill and tarsus of Piscivorous birds
No. Species Length of Bill Length of Tarsus
(mm) (mm)
1. Large cormorant 57-72 62-71
2. Indian shag 50-61 47-52
3. Little cormorant 29-34 35-40
4. Darter 74-90 42-47
5. Grey Heron 109-135 140-162
6. Purple Heron 115-144 121-145
7. Pond Heron 60-67 60-64
8. Cattle Egret 50-66 82-92
9. Large Egret 110-135 170-215
10. Median Egret 73-97 122-148
11. Little Egret 79-91 99-110
12. Night Heron 65-80 65-75
13. Painted Stork 252-278 240-250
14. Openbill stork 153-162 140-150
15. White Ibis 139-170 99-115
16. Spoon bill 180-228 130-165
17. WhiteBreasted Kingfisher 56-63 15-16
18. Common Kingfisher 42-46 8-10
124 RESULTS AND DISCUSSION
FORAGING BEHAVIOUR:
Understanding the ecological aspects of foraging requires use of a standardized nomenclature and knowledge on the distribution of various behaviors among piscivorous birds. The use of various mechanisms for catching prey depends in part on a species’ morphological and physiological adaptations and on the availability of various types of prey spacing system ranging from wide dispersion to aggregation, correlated with the nature and defensibility of the food resources. Aggregative foraging leads to behavioral associations such as commensalisms and prey robbing (Kushlan 1978a).
SWIMMING BIRDS
Among the swimming birds, the Large Cormorant, shag and Little Cormorant forage solitarily but those from large populations forage in groups and exhibit synchronous diving. While diving in pursuit of fishes, just the head was submerged followed by rest of body, wings kept closed. Fishes were caught under water and the head raised above water surface holding them between mandibles with the hook on the upper mandibles often penetrating the lateral surface of the prey and swallowed the head first.
The Darter, found singly or in scattered twos and threes foraged by pursuit diving from the surface, propelling themselves with their feet and keeping their wings half open. Fishes were captured between mandibles and head was swallowed first.
The Great White Pelican does not dive for its food. Instead it catches its prey while swimming. The Great White Pelicans like to come together in groups of a handful of birds or so to feed, as they can thus cooperate and chase fish to one another. When this is not
125 easily possible for cocample in deep water where fish can escape by diving out of reach they prefer to forage alone. But the birds also steal food on occasion sometimes from other
Pelicans sometimes from gulls.
DIVING BIRDS
Kingfishers fish by diving from a perch or from hovering flight. When hovering, kingfishers usually fly parallel to the shoreline in a series of arcs with the hovering phase representing the peak of each arc before diving the beak first into the water in the manner described by most other observers. Alternatively, the bird dives straight into the water. In successful dives if the fish was less than 20 mm long it was swallowed on the wing otherwise it was carried to a firm perch where the fish was beaten and swallowed head first (Table - 4.2). When fishing from a perch, the bird perches motionless on an elevated branch, until the prey is sighted, and dives down to capture it and returns to the tree to immobilize it by hammering it on the branch (Douthwatie 1976, Whitefield and Blaber
1978a). Fishes were normally captured at right angles to the longitudinal axis of the bill and could be stunned easily because the head of the fish is projected from the side of the beak.
126 Table - 4.2 Hunting distances and methods of feeding by Kingfisher
Common Kingfisher White breasted Kingfisher
Hovering height between 1-5(m) 2-25(m)
Distance between the perch 1-7 (m) 2-30(m)
and the water surface
Distance between the <25 (m) Unlimited
shoreline and the hovering
site
Swallowed on the wing 127 (47 %) 82 (21 %)
Swallowed on the Perch 140 (55 %) 327 (82 %)
Total observations (n) 300 425
WADING BIRD
About 38 feeding methods are used by various species of wading birds (Kushlan
1978). It is generally known that some wading birds posses a varied foraging repertoire and engage in the more active feeding behavior (Meyerriecks 1960, 1962, Kushlan 1978b,
Recher and Recher 1968, 1972, 1980). However, only a few studies have quantitatively determined the frequency with which each species uses these feeding techniques
(Willard 1977) or whether their use varies with environmental parameters (Hafner 1982)
Rodgers Jr. (1983) described the efficiency and frequency of feeding methods among species, age classes, colour phases and different environmental conditions.
127 Plate: 4.1
Feeding of large cormorant
1) Large cormorant catches the fish
2) A cormorant foraging by diving method
128 Plate: 4.2
1) Glossy Ibis catching the fish in the shallow water
2) Median Egret (in non breeding season) catching the fish with
sparse vegetation
129 Plate: 4.3
1) Wading birds like Painted Stork’s foraging by walking slowly
through shallow water
130 TYPES OF FEEDING BEHAVIOR
The methods adopted (as per Kushlan 1976a) for feeding by herons, egrets, storks, ibis and spoonbill are grounded into 13 categories. And the frequency of the use of each method is given in (Table 4.3):
1) Stand and wait (sw): A bird stands motionless in water waiting for prey to
approach.
2) Walk slowly (ws): moves slowly, stalking prey.
3) Walk quickly (wq): walks at relatively fast speed.
4) Running (Ru): moves quickly after a specific prey item.
5) Foot stirring (fs): Vibrates the tarsus in the water in soft mud.
6) Foot peddling (fp): Moves foot up and down.
7) Probing (Pr): quickly and repeatedly moves bill tip into and out of water.
8) Bill vibrating (BV): Rapidly opens and closes bill in water.
9) Diving (DI): Dives head first from perch.
10) Leap frog feeding (LF): Flies from back of feeding flock to front.
11) Aerial feeding (AF): while flying puts head first and catches prey.
12) Head swaying (HS): Moves head from side to side out of water, in either slow or
rapid sweeps.
13) Groping (GR): Places and holds bills opened in water.
131 Table-4.3 Occurrence of types of feeding behaviors among species
of Wading birds at Thol sanctuary
No. Sp./Behavior SW WS WQ RU FS FP PR BV DI LF AF GR HS
1. Grey Heron * * * ------* * - -
2. Purple Heron * * * ------
3. Pond Heron * * ------* * * - -
4. Night Heron - - * - - - - - * - - - -
5.CattleEgret - * - * - * * - - - * - -
6. Large Egret * * * - * * ------
7.LittleEgret - * * * * - * ------
8. Median Egret -***-----**--
9. Painted stork - * * * * * * - - - - * -
10. Openbill -**---*----*-
Stork
11. White Ibis - * * - - - * - - - - * -
12. Glossy Ibis - * * - - - * - - - - * -
13. Spoon bill - * * * - - * - - - - - *
Fig-4.3 LEGENDS
* = occurs SW = Stand and Wait BV = Bill Vibrating
- = does not occur WS = Walk Slowly DI = Diving
WQ = Walk quickly LF = Leap frog feeding
RU = Running AF = Aerial feeding
FS = foot stirring GR = Groping
FP = foot peddling HS = Head swaying
PR = Probing
132 The Grey Heron, Purple Heron, Pond Heron and Large Egret fed mainly by the method “stand and wait” and “walk slowly”. The Little Egret and Median Egret fed mainly by walk slowly, “walk quickly” and “running”. The major feeding techniques of the cattle Egret were walk slowly and running (35% and 29% resp.).The Night Heron exhibited the highest frequencies of “walk quickly” (33%) and “diving” (30%) methods.
The painted stork, Open bill Stork and White Ibis fed mainly by probing the most sedentary forager was Spoonbill, which spent over 60% of its time engaged in the head swaying method.
Major feeding techniques adopted by wading birds in the present study were similar to other reports (Table-4.5) which indicate that there is not much variation in feeding techniques in different habitats and seasons.
All species used only a few foraging methods. The Painted Stork used seven methods. The least number of feeding techniques (three) was used by the Purple Heron
(Table-4.4).
Most of the wading birds showed some tendency to change the frequency of foraging methods with different habitats (Table-4.4) each species used one or more feeding techniques and this apparently helped the bird to utilize the resources from different zones. The aquatic area could be divided broadly into four habitats namely
(1) Open water (OW), (2) Shallow water + sparse vegetation, (SWSV) (3) Thick vegetation (TV), and (4) Edge of the dyke and mound. (EDDM).
133 Table -4.4 Inter-specific comparison of the percentage frequency
of feeding behaviours
Piscivorous No. SW WS WQ RU FS FP PR BV DI LF AF HS « GR Birds
1. Grey Heron 55 30 10 0 0 0 0 0 0 5 0 0 1 0
Purple 2. 65 30 5 0 0 0 0 0 0 0 0 0 0 0 Heron
3. Pond Heron 45 15 10 0 0 0 0 0 15 10 5 0 0 0
4. Cattle Egret 0 20 40 30 0 0 0 0 0 10 0 0 1 0
5. Large Egret 40 30 10 0 5 0 0 0 0 0 10 0 5 0
6. Little Egret 0 30 20 10 13 0 0 12 0 8 7 0 0 0
Median 7. 0 50 15 0 0 0 0 0 0 17 13 0 5 0 Egret
Painted 8. 1 15 17 0 10 5 35 0 0 0 0 0 3 15 Stork
9. White Ibis 0 5 20 0 0 0 70 0 0 0 0 0 0 5
10. Spoon Bill 0 10 5 15 0 0 0 0 0 0 0 70 1 0
LEGENDS SW = Stand and Wait PR = Probing
WS = Walk Slowly BV = Bill Vibrating
WQ = Walk Quickly DI = Diving
RU = Running LF = Leap Frog Feeding
FS = Foot Stirring AF = Areal Feeding
FP = Foot Peddling HS = Head Swaying
« = Other techniques exhibited < 5% 134 Fig.-4.4 Inter-specific comparison of the frequency of
feeding behaviours
Grey Heron
Purple Heron
Pond Heron
Cattle Egret
Large Egret
Little Egret
Median Egret
Painted Stork
White Ibis
Spoon Bill
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
SW WS WQ RU FS FP PR BV DI LF AF HS «
135 Table-4.5 Similarity of feeding behaviour of various birds between Thol bird sanctuary and elsewhere
Grey Purple Pond Night Cattle Large Medium Little Painted Openbill White Spoonbill
Heron Heron Heron Heron Egret Egret Egret Egret Stork Stork Ibis
SW 1,3,8,28 8,7,19 7,8 7,28 3,7,8,16,15,17,12,
WS 7,3,28 8,7,19 7,8 7,28 7,8,16,25 7,8,16,15,17,12, 7,8 1,2,16,7,8,28 24
WQ 3 7,12 8 3,7
RU 7 7,14,25 3 3,7 8 8
FS 7 21,3,7,28
RP 7 8
PR 7 8 8 8,20 8,24,26,21
BV 7 7
PI
IP 8,18 9,13 16 8
AP 29 6,7 7 7,10,11,30 7,6 4,6,5
136 GR 8
HS 8
1. Refner et al. (1982) 9. Wise and Grawfor (1973) 17. Willard (1977) 25. Blaber (1969)
2. Erwin et al. (1935) 10. Rodgers (1984) 18. Keyerriecks (1960) 26. Kushlan (1979)
3. Whitefield ana Blaber (1978) 11. Meyerricks (1952) 19. Tomilinson (1975) 27. Kushlan (1986)
4. Abdulali (1967) 12. Rodgers Jr. (1983) 20. Kahl (1971) 28. Fasola (1986)
5. Mathew (1983) 13. Gladstone (1977) 21. Kahl (1973) 29. Marshall (1961)
6. Sivasubramaniam (1988) 14. Jenni (1960) 22. Kahl (1972)
7. Kushlan and Hancock (1980) 15. Recher and Recher (1980) 23. Sivasubramaniam et al. (1989)
8. Ali and Ripley (1983) 16. Recher et al. (1983) 24. Kushlan (1977)
137 CHAPTER-5
BREEDING BIOLOGY OF THE
PISCIVOROUS BIRDS CHAPTER – 5
BREEDING BIOLOGY OF THE PISCIVOROUS BIRDS
Introduction
The Thol Bird Sanctuary provides an ideal habitat for the colonial nesting birds.
There are dynamic locations inside the TS where they nest every year. In the present study, details on breeding biology of the colonical breeders of Thol Bird Sanctuary were gathered to examine the number of birds breeding inside the sanctuary and their major breeding requirements.
Most piscivorous birds are colonial nesters except kingfisher (hole nester).
Colonial nesting is widespread among water birds, but relatively rare among terrestrial birds (Lack 1966).
Considerable work has been done on the breeding biology and nesting requirements of many colonial birds at several places. Breeding biology of White breasted
Cormorant Phalacrocorax carbo was studied by Olver and Kuyper (1978) and Reed
Cormorant Phalacrocorax africanus by Olver (1984), Bank Cormorant by Cooper (1985b,
1987) and Shag Phalacrocorx aristotalis by Snow (1960). Grey Heron Ardeo cineria has been studied by Verwey (1930), Lowe (1954), Owen (1960), Milstein et al. (1970) and of
Purple Heron Ardea purpurea by Steinfatt (1939) and Tomlinson (1974a, 1974b, 1975).
The breeding biology of the Sacred Ibis has been studied by Urban (1974) and Spoonbill by Kahl (1983) and Donald et al. (1982).
138 There is very little quantitative information available on breeding biology of the colonial birds in India. Ali and Ripley (1968) gave general information on the nidification.
Singh et al. (1988) described the breeding biology of Painted stork and Openbill stork in
Bharatpur. Desai et al. (1978) studied the reproductive pattern of Painted stork in Delhi zoo. Mukhopadhyay (1980) described the breeding biology of Openbill stork in Southern
Bengal. Parasharya (1984) did a detailed study on the breeding biology of some
Ciconiformes in selected coastal areas of Gujarat. Sivasubramaniam (1992) reported the basic data on the breeding biology of the colonial nesting birds of Keoladeo National Park.
Dave (2002) reported the breeding biology of the colonial nesting birds at Rajkot in
Saurashtra.
METHODOLOGY:
During the present study nests were observed every 15 days at the nesting sites. All nests were on the trees. All these nests were at different heights and in different canopies of the trees. When the birds started to build the nest, the nest was given a number at all selective sites. This number was maintained till the end of the nesting cycle and it was considered as a nest number. The observations were recorded nest-wise on data sheets.
During egg laying period the observations of the nest was difficult sometimes. A boy was employed to climb up the trees or in certain cases a set of mirrors on the pole was used to observe the nest activities.
139 NEST LOCATION
There are three major nesting sites in the study area.
(1) Site A: This site is situated in northeast direction. Near this site, there are oil wells
belonging to ONGC. Trees include Neem - Azadirachta indica, Desi Baval -
Acacia nilotica, Gando Baval- Prosopis chilensis, Mithi Pilu - Salvadora oleoides,
Akdo - Calotropis gigantea etc. Wading birds' nesting was also seen here.
This is second largest colony of heronry in the sanctuary. The mounds are
situated 23 meters apart. Each mound has about 4-8 Acacia nilotica probably
because of crowding of trees on the mounds, they slant towards the water,
obviously for more light. 29 mounds were usually used by the nesting birds in the
area. 10 species of birds nested here; the most common among them were the
Openbill Stork (40) followed by the Indian Shag (20) Darter (2) Egrets (70) and
Herons (150), Pelicans (5) (2005)
(2) Site B: This site is situated near Jethlaj village, where whole area is covered with
Acacia nilotica trees having big nesting colonies of waders like Egrets, Herons, Spoonbill,
Ibis and swimmer’s like Cormorants on this site. Trees include Rayan - Manilkara hexandra, Baval - Acacia nilotica, Mithi pilu - Salvadora oleoides, Khari pilu - Salvadora persica, etc. are seen here.
This is first largest colony of heronry in the sanctuary. The nests were located on a total of approximetly more than 550 trees mainly Acacia nilotica. The largest number of nests in this area was the Indian Shag (300),Little Cormorant (400) Large
140 Cormorant (100) Spoonbill (200) Painted Stork (30) Darter (3) Egrets (250) Herons (70)
Ibis(50) were seen.
(3) Site C: This site is located on the front side of watchtower. The site is fully open
and having deep water. In certain areas of upper region, dense trees and other
vegetation cover was observed which is a favorable site for birds for resting and
roosting. There is a nesting site for some waders too. It is also Pelicans' favorite
resting place. In monsoon, water depth is about 6 to 8 feet and during winter, level
of water comes to 4 to 5 feet and in summer, it dries up to form small puddles.
Dense vegetation and big trees like Limdo - Azadirachta indica, Desi Baval -
Acacia nilotica, Mithi pilu - Salvadora oleoides, Piplo - Ficus religiosa, Herb -
Dholo, Dhanturo - Datura metal, Bhoy Ringani - Solanum surattense, Mindhi aval
- Cassia ilalica, Shurb - Nano akado - Calotropis procera, Akdo - Calotropis
gigantea etc. are found here.
About more than 150 trees closed formed the third major colony. The
largest number of nests in this area was of Spoonbill (200) Painted Stork (50) and Ibis
(100). The white Ibis had its largest number of nests here.
141 Plate: 5.1
1) A Darter during the nesting phase
2) A Darter keeping guard on it’s nest with three juvenile
142 Plate: 5.2
1) Pelicans nest with four chicks
2) Chicks on a large platform on a Banyan tree
143 Plate: 5.3
The great white pelican looks after its nest
144 Plate: 5.4
1) A large nesting colony (site- b) on the Acacia trees
1) Egret`s juvenile is seen in the nest
145 Plate: 5.5
The Openbill stork collecting the nesting material in the heronaries.
146 Plate: 5.6
A Spoonbill’s nest
147 Plate: 5.7
1) The juvenile of Little Heron leaves the nest and is learning to fly
2) A juvenile of a White Ibis
148 Plate: 5.8
1) During the nesting phase White Ibis’s Chicks waiting for it`s food
from their parents
149 Plate: 5.9
1) A large nesting colony of Painted Storks
2) Openbill Stork`s juveline waiting for food.
150 Plate: 5.10
Marending Crows are the biggest predators of the chicks
151 RESULTS AND DISCUSSION
Table-5.1 Breeding schedule of the Heronries during 2005-06
No. Species Initiation Peak of End of No. of weeks Average
of Nesting Nesting Nesting of nesting No. of
week week week (n) Nests
A B C D
1. Large cormorant Aug. 1st Sept. 1st Nov. 3rd 15 150
2. Indian shag July 1st Sept. 2nd Oct. 3rd 15 320
3. Little Cormorant June 4th Sept. 1st Sept. 3rd 12 450
4.. Darter July 1st Sept. 2nd Nov. 4th 13 07
5. Grey heron July 1st Sept. 2nd Nov. 1st 17 20
6. Purple heron July 3rd Sept. 3rd Nov. 4th 18 35
7. Cattle Egret June 2nd Aug. 3rd Aug. 4th 10 220
8. Large Egret June 4th Aug. 4th Oct. 4th 17 175
9. Median Egret June 3rd Aug. 3rd Oct. 3rd 17 150
10. Little Egret June 3rd Aug. 3rd Oct. 3rd 17 275
11. Night heron July 1st Sept. 1st Sept. 4th 12 25
12. Painted stork Aug. 3rd Sept. 4th Feb. 2nd 24 125
13. Openbill stork May 4th Aug. 3rd Oct. 1st 18 50
14. Spoonbill June 3rd Aug. 4th Oct. 2nd 16 325
15. White Ibis June 4th Aug. 3rd Oct. 2nd 15 275
152 NOTE :
A. Week when the earliest nests were started.
B. Week when the maximum number of active nests were recorded.
C. Week when the last chicks left the nests.
D. Maximum number of active nests seen at the peak season.
Table-5.2 Clutch size and nesting cycle of the Heronry species
No. Species Clutch Nest Egg Incubation Nestling Complete
Size Building laying period period Nestling
period period (days) (days) cycle
(days) (days) (days)
1. Large 3-5 6-8 3-7 22-24 40-45 60
cormorant
2. Indian shag 3-5 5-8 6-7 26-28 42-47 58
3. Little 2-4 5-8 6-7 22-26 40-43 62
Cormorant
4.. Darter 4-5 6-9 6-7 23-26 43-48 72
5. Grey heron 3-4 5-7 5-7 23-25 41-47 62-70
6. Purple heron 3-5 5-7 5-7 23-26 40-42 70-85
7. Cattle Egret 3-5 5-10 5-7 22-24 42-49 75-85
8. Large Egret 3-4 4-10 5-7 25-26 42-49 76-95
9. Median Egret 2-4 4-11 5-7 22-23 38-42 70-80
153 10. Little Egret 2-4 4-7 5-8 21-23 42-43 75-85
11. Night heron 3-4 3-7 5-6 21-23 41-48 71-87
12. Painted stork 3-4 5-7 5-7 29-32 115-125 153-162
13. Openbill stork 4-5 5-11 5-8 28-30 100-122 80-95
14. Spoonbill 3-4 7-8 5-7 22-26 48-52 75-84
15. White Ibis 3-5 7-8 5-7 23-27 43-50 75-85
BREEDING SEASON OF THE COLONIAL WATER BIRDS
A generalized account of the breeding season and timings is given for individual
heronry species in the Indian subcontinent by Ali and Ripley (1968). The breeding seasons
of some individual species at inland sites are given by Lamba (1963), Bhatia and Desai
(1971), Desai et al. (1978), Breeden and Breeden (1982a, b) Salim Kumar (1982) and
Parasharya (1984).
All the species, except the Grey Heron and Purple Heron had only one breeding
season which was in the monsoon. The Grey and Purple Herons breed in summer also
depending upon the availability of water and fish inside the lake during this season.
However, in the summer of 2006, the Little Egret, Median Egret, Little Cormorant, Indian
Shag and Darter also bred, although in small numbers. A substantial quantity of water was
available during the summer of 2006. Sometimes, the breeding of Grey Heron and Purple
Heron in summer was due to the failure of nesting in the breeding season or whether it was
a second brood is uncertain. Hancock and Kushlan (1980) and Tomilnson (1974a, b)
reported that double breeding is rare in Grey Heron and Purple Heron.
154 Breeding of all heronry species, except the painted stork, begins in July and extends up to October depending on the onset of rain and time of release of water from the
Eastern canal. The painted stork is a late breeder, starting towards the end of August or the beginning of September and extending up to November or early December. Breeding season, breeding schedule and breeding cycle are summarized in Table-5.1, 5.2.
The proximate factors which trigger off breeding in all the species, except the
Openbill stork were the inundation of the area and the appearance of a large number of fry and fingerlings in the vicinity of the nesting site. Apparently openbills begin breeding only after flooding, as it increases the availability of their food supply by bringing the Pila
Snails out of aestivation (Saxena 1956).
During 2005, the nesting of Openbill stork was observed. The Openbill stork was the first to arrive at the nesting site. They do so just before the onset of monsoon and begin to build the nest but many waited for laying till the area was inundated. If monsoon fails they don’t breed that year.
Pelicans are also colonial breeders. These birds arrive in late winter and their breeding season continues from February to April. End of February or early of March, they start construction of nest. In the present study only four pairs that built the nests on the banyan tree. They made a large platform in top part of trees. The nest is a shallow depression scraped on the tree in which some twigs, sticks, reeds or similar debris are gathered. After about one week of courtship and nest building, the female lays a clutch of usually 3 or 4 eggs.
155 Both the parents incubate for about 4 weeks. The young leave the nest 3-4 weeks after hatching. At this point, usually only one young per nest has survived. They spend the following month in a crèche or “Pod”, moulting into immature plumage and eventually learning to fly. After fledging, the parents care for their chicks (Plate-5.3) some three more weeks until the close family bond separates in late summer or early fall and the birds gather in larger groups on rich feeding grounds in preparation for the migration.
REGULATION OF NESTING SEASON
A large number of studies made on the breeding patterns of birds have indicated that every species of bird tends to bread at the time of the year when it can raise its young most efficiently (Lack 1954, 1966). Those environmental factors that control efficiency of breeding are called "Ultimate Factors" (Thomson 1950). The most important ultimate factors for nearly all species of birds are the availability of adequate food supply. In the present case the ultimate factor which determines the breeding season of all the wading birds appeared to be the drying up of areas and the subsequent concentration of fish and other organisms in shallow pools in comparatively deeper areas. Such mechanical concentration of prey appears to be essential for any successful breeding in wading birds
(Kahl 1964, Kushalan et al. 1975). Both, the timing of breeding and the degree of breeding success may be strongly affected by the rate of drying which concentrate the prey
(Kushaln et al. 1975, Clark and Clark 1979).
The food supply or its availability apart from being the most effective ultimate factor apparently has an immediate influence on egg laying. For most species, the production of eggs may depend upon the ability of females to collect the store nutrients prior to the nesting attempt. (Ankney and Mac James 1978, Winkler and Waltes 1983,
156 Eldridge and Krapu 1988).Circumstantial and experimental evidence for the importance of nutritional factors in spermatogenesis and egg laying are discussed by Marshall (1949),
Siivonen (1957), Assenmachar et al. (1965), Loft and Murton (1966), Lack (1967) and
Braithwaite and Frith (1970).
NEST BUILDING
The availability of nest building material was plenty in Thol Lake. Dry branches and twigs of plants scattered on the ground were used for nest building. The nesting material was re-used very commonly. Any nest abandoned during the nesting season was occupied as such by a nesting pair, or it became a convenient source of material for the nest- building in progress elsewhere.
Often if any nest in the vicinity was left unattended, a bird at a nest would steal the material and add it to its own. Inter-specific stick steeling from the unguarded nest was observed in many cases. Similar observation was made on Ardeola ibis (Valentine 1958,
Blaker 1969a), for Great Blue Heron by Pratt (1972) and Mock (1976), Great Egret by
Mock (1978), Reed Cormorant by Olver (1984) and for Whitebreasted Cormorant by
Olver and Kuyper (1978).
Little cormorant, Cattle Egret, Median Egret, Little Egret and Night Heron usually steal the materials from nests of co-specific neighbors only. On the other hand, the other birds were prone to steal the material not only from the co-specific neighbor, but also from nests of the other relatively smaller species. The stick stealing birds could dismantle an unguarded nest within a day or two, and they even ejected the eggs or chicks during the process. In such a raiding and robbing operation, social dominance based more or less on
157 size of the inter-acting birds became operative. Dominance in this context refers to the priority of success to resources that results from successful attacks, fights or supplants and social dominance refers to inter-specific interactions (Morse 1974).
Mock (1976) observed that the Great Blue Heron (Ardea herodias) stole most of the nest material from the nearby nests so the mates never lost visual contacts with each other. Mock (1978) also recorded stick stealing in Casmerodius albus. Keeping the mate in visual contact might help to strengthen the pair pond especially in the situation when otherwise the male has to go long distances for collecting the nest material. The other two subsidiary functions of the stick stealing could be the saving of energy by avoiding long distant collecting trips and reducing the chances of predation.
NESTING PATTERN
It is usually the Openbill stork which first arrives at the nesting sites and occupies the nesting trees. Although most species can be seen in both the large & small heronries, some show a striking preference to a particular colony. The painted stork often keeps away from other species. The white Ibis prefers a particular B site within a colony.
PARENTAL CARE
FEEDING THE CHICKS
In Cormorants and Darter, the chicks were fed on fish by both parents. Food was regurgitated in small amounts into the open mouths of the chicks during the early stages of development. At about two weeks of age, the chicks started to help themselves by
158 inserting their bills deep into the gullet of the parents. The parents were also seen regurgitating water into the chick’s mouth.
In wading birds, freshly hatched chicks responded to the tactile and auditory stimuli. They tried to stand erect on their weak legs with the support of the big abdomen, raised the beak and gave short "Chick Chick" call. The adults regurgitated the food on the nest floor, and the chicks in early stages, pecked the regurgitated matter and the chick even begged at the parent's beak when it regurgitated. If the regurgitated food items were too large for the chicks to swallow, the parents re-consumed them. As the chicks grew older, the "chick chick" call became louder and was accompanied by the sidewise rocking movement of the body. Older chicks grabbed the beak of the parent and pulled it down violently to make them regurgitate. The chick grabbed the parents beak across the base so that the regurgitated food directly passed on to it beak.
In white ibis, the young bird usually responds by increasing the volume and increasing the frequency of its begging call, and by stretching and wobbling its neck and head towards the adults. Then, sometimes with the aid of the parent, the young bird places its bill into the parents partly-opened bill and moves its bill among the edge of the adults bill until the head end anterior part of its neck are hidden inside the adults mouth cavity.
Feeding then takes place.
In cormorants and storks, the parents were also seen regurgitating water into the chicks mouth, especially on hot days and this was observed in the Reed Cormorant
Phalacrocorax africanus (Olver 1984), White- breasted cormorant , Phalacrocorax carbo
159 (Olver and Kuyper 1978), Openbill Stork by (Kahl 1971c) and Blacknecked Stork
(Kahl 1971c, 1973).
GUARDING THE NEST
At least one parent actively guarded the chicks till they attained the age of 15 to 20 days. After that, the parent took up a perch some distance away from the nest and guarded the chicks for a further period of 5 to 10 days and than finally left the chicks unguarded.
Thereafter, the parents returned to the nest only to feed the chicks or roost at night.
THERMOREGULATION
In most species, the adults shade small young much as they shade eggs. For example, as the ambient temperature rises the parent stands over the nest, facing away from sun, often angles the bill slightly skyward, flutters the gular area and lowers the wings, which shade the young. During the hot hours of the day, almost all the guarding birds in the colony were found keeping their face in the same direction. Direction of the guarding bird changed with the position of the sun. The parents shading the chicks stood at the edge of the nest, often keeping the legs flexed. Both the wings were partially or fully kept loose so as to create a canopy under which the chicks were shaded. As the birds were also susceptible to the sun heat, it seemed that the wing drooping posture had not only the function of shading the chicks, but it also gave passage to the wind to pass through and helped the bird in self thermoregulation. Kahl (1971) suggested that it is probable that the function of shading the contents of the nest is often combined with self-thermoregulation of birds by the spread-wing posture over egg or young in hot weather. The adult and chicks started gular fluttering during the hot hours and such behavior was reported in Reed
160 Cormorant by Olver (1984), White breasted cormorant by Olverer and Kuyper (1978) sacred ibis (Threskierns aethiopica) by urban (1974).
On several occasions, particularly during the warmest part of the day, the adult cormorants and storks were seen regurgitating water in the nesting or drool it over the egg.
This behavior was noted in Openbill stork (Kahl 1971c), Blacknacked stork (Khal 1971c,
1973), Adjutant stork (Leptoptilos javanicus) Kahl (1971c), Marabou stork, whitebreasted cormorant (Olver and kuyper 1978) and Reed Cormorant (Olver 1984), whether this was mainly to cool the eggs or to maintain a proper humidity is not known.
PREDATION
Predation has frequently been implicated in the failure of heronry species (Dusi and Dusi, 1967; Jenni, 1969; Pratt, 1972; Rodgers, 1987). The major predators in the area during the egg laying period were crows (Plate-5.10) and during nesting period main predators were Eagles and Marsh Harrier. During the incubation period the parent bird deserts the nest at the approach of man. Eggs from these nests became vulnerable to the crows. However, the parents do not desert the nest once the eggs are hatched as reported elsewhere (Dusi and Dusi, 1967). During this period causality of chicks could occur if man goes very close to the nest, the chicks become panicky and may fall into the water.
Chicks also fall from the nests due to the heavy wind or stormy weather and rain.
Some chicks were found hanging dead on the nest rim after heavy wind. Some chicks died just because their one leg got trapped in a narrow branch.
161 ASYNCHRONOUS HATCHING
In a brood of three, the two older chicks were larger than a third chick. The younger chick remained very small for a longer time and remained in the nest, while the elder two roamed around the nesting tree. This difference in the growth of chicks was due to the asynchronous hatching. The chicks hatched in the sequence in which the eggs were laid. Therefore, the age difference between two chicks was quite often more than 5 days.
The parents feed the elder chicks which begged vigorously. So the younger chicks which got less food remained smaller in size for a long time and even died due to starvation.
162 SUMMARY SUMMARY
Piscivorous Birds are important components of wetland ecosystem as these birds are at a relatively higher level in the food chain and represent a variety of predatory niches. According to the feeding habits, the Piscivorous birds are grouped into three categories, swimming birds (Pelecanidae and Phalacrocoracidae), wading birds (Ardeidae, ciconidae and Threskiornithidae) and diving birds (Alcedinidae).
The present study was conducted in Thol Bird Sanctuary, Kadi Taluka, Mehsana
District, Gujarat, one of the famous sites for its wintering congregation of waterfowl and massive colonies of nesting heronry species. The field study was conducted from January
2005 to January 2007.
Major objectives of the present study are: 1) to know the status of various bird species by population assessment 2) to assess the habitat availability to various group of birds 3) to assess the feeding methods adopted by birds to adjust to the environment. 4) to assess breeding requirement and availability of resources in the area 5) to know the ecological factors like water level, pH and salt contents, aquatic plants, fishes etc.
The population was assessed by direct counting of birds in all the aquatic sites out of 23 species of fish eating birds, six species are swimming birds which contributed 35 % of the overall population. Thirteen species of wading birds contributed about 63 % of the population, and 2 % was contributed by the diving birds. Among all the fish eating birds the highest number was of Pelicans followed by Indian shag. The Little blue Kingfisher was the lowest in number. The highest average population of fish eating birds was in 2006
163 reaching the maximum number, in 2005 it was lowest. There is significant positive relation between total population of Piscivorous birds and water depth, the fluctuation in the water regime and related alternations in the habitat.
Habitats were classified into 6 types according to the dominant plant community and water regime. The preference for a particular habitat by different species and utilization of each habitat by them were studied by visiting various habitats regularly and recording the occurrence of each species of swimming birds that preferred open water the most, followed by shallow water + sparse vegetation for feeding. The Grey Heron and
Purple Heron preferred shallow water + sparse vegetation and the Night Heron and Pond
Heron did so mainly the edge of the dykes and mounds for feeding. All egrets except the
Cattle Egret preferred mainly shallow water + sparse vegetation for feeding. In the case of the Cattle Egret the most preferred habitats were newly flooded area and grassy patch.
Painted Stork used mainly the sparse vegetation for feeding. The Openbill Stork preferred mainly puddles for feeding. Large number of white Ibis, few of in shallow water + sparse vegetation, grassy patch and Grass + Ipomea. The highest numbers of Spoonbill were in shallow water. Common Kingfisher preferred shallow water + sparse vegetation and the white breasted Kingfisher the reed beds. Among 12 species of wading birds, the Open bill
Stork had more specific habitat requirement while Large Egret, Little Egret and Pond
Heron had more flexibility in their habitat.
Food and feeding habits of the Piscivorous birds were studied by observing the birds directly during different hours of the days. The swimming birds forage solitarily, but those from large population forage in groups and exhibit synchronous diving. The diving bird’s fish by diving from a perch or from hovering flight "Stand and wait", "walk
164 slowly", "walk quickly" and "running" were the major feeding techniques of the herons and egrets. The two species of storks and white Ibis fed mainly by "probing". The
Spoonbill exhibited the highest frequencies of "Head Swaying Method". The Large Egret, the Little Egret and the Painted Stork used eight methods. The last number of feeding techniques (3) "Walk Quickly" was used by Purple Heron. Feeding behavior of the wading birds related to the depth at which they foraged and the presence or absence of aquatic macrophytes.
Of the 23 species of Piscivorous birds, 14 were colonial breeding. Site A & Site B were the colonial water birds' nesting sites frequently. There are two breeding seasons for colonial breeders, one in monsoon and the other in summer. All the species, except the
Grey Heron and Purple Heron, had only one breeding season which was in the monsoon.
The Grey Heron and Purple Heron bred in summer also. Breeding of all heronry species, except the Painted stork begin in July and extends up to October. The Painted stork starts towards the end of August. The date of release of water is also equally important. The time of release of water does have a role in the nesting success of a various species. The major predators during the egg laying period are eagles. The population and breeding success of these colonial breeders in this sanctuary mainly depend on the quantum of annual input of water, time of release and recruitment of fry into the sanctuary. The proximate factors which trigger off breeding in all the species were the inundation of the area and the appearance of a large number of fry in the nesting site. The food supply or its availability apart from being the most effective ultimate factor apparently has an immediate influence on egg laying. Ecological parameters such as date of water release, quantum of water input and fish fry were correlated with the nesting success.
165 The time of release of water determines the annual cycle of many of the heronry species.
The extent of water spread area affects the breeding seasonality of most of the heronry species. Maintenance of a particular water level or definite quantum of water supply every
year would help in breeding of many bird species. The staple food for the adult as well as
chicks of almost all the heronry species is fish. Therefore the influx of fish fry with water from the canals determines the breeding success. The appropriate time for water release is
July, so that birds get adequate time to lay and raise the chicks before winter. From the
study it is understood that the water management and control of aquatic vegetation are
very essential for the survival of all the heronry species.
166 APPENDIX - I
FLORA:
A Check list of the macrophytes (aquatic and terrestrial) recorded at TS:
Scientific name Local Name Form
1 2 3
MENISPERMACEAE
Cocculus hirsutus Vevdi H
CAPPARACEAE
Capparis deciduas Kerdo S
Capparis sepiaria Kanther S
Cleome viscose Pili Talavani H
ELATINACEAE
Bergia ammannioides H
Bergia suffruticosa Ropatri H
MALVACEAE
Suaeda sp. -H
TILIACEAE
Corchorus aestuans Chunch H
Corchorus fascicularis -H
Corchorus olitorius -S
Corchorus sp. -H
167 ZYGOPHYLLACEAE
Tribulus terrestris Bethu Gokhru H
BALANITACEAE
Balanites aegyptiaca Ingorio, Hingoriyo T
MELIACEAE
Azadirachta indica Limdo T
CELASTRACEAE
Maytenus emarginata Viklo S
RHAMNACEAE
Zizyphus nummularia Chani Bor S
SAPINDACEAE
Cardiospermum halicacabum Kagdoliyo CI
ANACARDIACEAE
Mangifera indica Ambo, Keri T
PAPILIONACEAE
Alhagi pseudalhagi -S
168 Scientific name Local Name Form
1 2 3
Alysicarpus sp. -H
Butea monosperma Khakharo T
Crotalaria burhia Kharshan S
Derris indica Karanj T
Indigofera linnaei Fatakiya H
Indigofera oblongifolia Zil. Ziladi S
Melilotus alba Jungli Methi H
Melilotus indica -H
Rhynchosia minima Nani Kamalvel Tw
Tephrosia purpurea Sarpankho H
Trigonella occulta -H
CEASALPINIACEAE
Bauhinia racemosa Asotri T
Cassia auriculata Aval S
Cassia fistula Garmalo T
Cassia italica Mindhi Aval H
Cassia occidentalis Kasundri H
Cassia roxburghii -T
Cassia siamea -T
Cassia tora Kuvandio H
Tamarindus indica Amli T
MIMOSACEAE
169 Acacia nilotica Desi Baval T
Acacia sp. -T
Albizia odoratissima Dholo Sirisi T
Neptunia oleracea Lajalu H
Prosopis cineraria Khijado T
Prosopis chilensis Gando Baval S/T
CUCURBITACEAE
Coccinia grandis Ghiloda CI
Mukia maderaspatana Chanak Chibhdi CI
Trichosanthes cucumerina Jangli Parval CI
MOLLUGINACEAE
Glinus lotoides Mitho Okharad H
RUBIACEAE
Oldenlandia sp. -H
ASTERACEAE
Amberboa ramose Bada Vard H
170 Scientific name Local Name Form
1 2 3
Eclipta prostrate Bhangro H
Grangea maderaspatana Zinki Mundi H
Launaea procumbens Moti Bhonpatri H
Sphaeranthus indicus Gorakh Mundi H
Tridex procumbens Pardesi Bhangro H
Vernonia cineraria Sahadevi H
Xanthium strumarium Gadariyu H
SAPOTACEAE
Madhuca indica Mahudo T
Manilkara hexandra Rayan T
SALVADORACEAE
Salvadora oleoides Mithi Pilu T
Salvodora persica Khari Pilu T
ASCLEPIADACEAE
Calotropis procera Nano akado S
Calotropis gigantean Akdo S
GENTIANACEAE
Enicostema hyssopifolium Mamejevo H
EHRETIACEAE
Cordia gharaf Nani Gundi T
171 BORAGINACEAE
Coldenia procumbens Basario Okharad H
Heliotropium indicum Hathisundho H
CONVOLVULACEAE
Convolvulus microphyllus Shankhavali H
Cressa cretica Khariyu H
Evolvulus alsinoides Kali Shankhavali H
Ipomoea aquatica Nada ni Vel H
Ipomoea fistulosa Naffat Val S
Rivea hypocrateriformis Fang CI
SOLANACEAE
Datura metal Dholo Dhanturo H
Solanum indicum Ubhi Ringani H
Solanum surattense Bhoy Ringani H
MARTYNIACEAE
Martynia annua Vinchhudo H
ACANTHACEAE
Justicia simplex -H
172 Scientific name Local Name Form
1 2 3
Lapidogathis trisnerivis Haran Charo H
Peristrophe bicalyculata Kali Anghedi H
VERBENACEAE
Clerodendrum multiflorum Arani S
LAMIACEAE
Ocimum basilicum Damro H
Ocimum canum Ran Tulsi H
NYCTAGINACEAE
Achyranthes aspera Andhedo H
Pupalia lappacea Lampadi H
CHENOPODIACEAE
Chenopodium album Chil Bhaji H
POLYGONACEAE
Polygonum plebeium -H
EUPHORBIACEAE
Euphorbia hirta Dudheli H
Euphorbia nivulia Thor S
Euphorbia orbiculata -H
ULMACEAE
Holoptelea integrifolia Kanjo T
MORACEAE
173 Ficus religiosa Piplo T
Ficus virens Pipal T
CYPERACEAE
Cyperus sp. -H
POACEAE
Cynodon dactylon Darba H
Eragrostis sp. -H
URTICACEAE
Ficus benghalensis Banyan Tree T
NOTES :
1: In addition to the plants, like Sesbania sp., Echinochloa colonum, Nymphaea
sp., (Common Lilly) and Astereacantha longifolia / Hygrophila auriculata) are
also recorded in the environs.
2: Abbreviations :
H: Herb S: Shrub T: Tree Tw: Twiner CI: Climber
174 APPENDIX - II
A. Waterfowl recorded during Phase-I (September 1999-March 2000) :
I. FAMILY : DENDROCYGNIDAE
1. Whistling – Duck Dendrocygna javanica
II. FAMILY : ANATIDAE
2. Greylag Goose Anser anser
3. Bar-Headed Goose Anser indicus
4. Ruddy Shelduck Tadorna ferruginea
5. Comb Duck Cairina scutulata
6. Eurasian Wigeon Anas Penelope
7. Mallard Anas platyrhynchos
8. Spot-Billed Duck Anas poecilorhynca
9. Northern Shoveler Anas clypeata
10. Northern Pintail Anas acuta
11. Common Teal Anas crecca
12. Common Pochard Aythya ferina
13. Ferruginous Pochard Aythya nyroca
14. Tufted Duck Aythya fuligula
III. FAMILY : ALCEDINIDAE
15. Common Kingfisher Alcedo atthis
IV. FAMILY : HALCYONIDAE
16. White - Throated Kingfisher Halcyon smyrnensis
V. FAMILY : CERYLIDAE
175 17. Pied Kingfisher Ceryle rudis
VI. FAMILY : STRIGIDAE
18. Brown Fish Owl Ketupa zeylonensis
VII. FAMILY : GRUIDAE
19. Sarus Crane Grus antigone
20. Demoiselle Crane Grus virgo
21. Common Crane Grus grus
VIII. FAMILY : RALLIDAE
22. White - Breasted Waterhen Amaurornis phoenicurus
23. Common Moorhen Gallinula chloropus
24. Common Coot Fulica atra
IX. FAMILY : SCOLOPACIDAE
25. Black - tailed Godwit Limosa limosa
26. Eurasian Curlew Numenius arquata
27. Spotted Redshank Tringa erythropus
28. Common Redshank Tringa tetanus
29. Marsh Sandpiper Tringa stagnatilis
30. Common Greenshank Tringa nebularia
31. Green Sandpiper Tringa ochropus
176 A. Waterfowl recorded during Phase-I (September 1999-March 2000) :
32. Wood Sandpiper Tringa glareola
33. Common Sandpiper Actitis hypoleucos
34. Little Stint Calidris minuta
35. Temminck's Stint Calidris temmickii
36. Ruff Philomachus pugnax
X. FAMILY : JACANIDAE
37. Pheasant - Tailed Jacana Hydrophasianus chirugus
38. Bronze - Winged Jacana Metopidius indicus
XI. FAMILY : BURHINIDAE
39. Great Thick – Knee Esacus recurvirostris
XII. FAMILY : CHARADRIIDAE
40. Black - Winged Stilt Himantopus himantopus
41. Pied Avocet Recurvirostra avosetta
42. Pacific Golden Plover Pluvialis fulva
43. Little Ringed Plover Charadrius dubius
44. Kentish Plover Charadrius alexandrinus
45. Lesser Sand Plover Charadrius mongolus
46. Red - wattled Lapwing Vanellus indicus
47. Sociable Lapwing Vanellus gregarious
48. White - tailed Lapwing Vanellus leucurus
XIII. FAMILY : GLAREOLIDAE
49. Small Pratincole Glareola lacteal
177 XIV. FAMILY : LARIDAE
50. Brown - Headed Gull Larus brunnicephalus
51. Gull - Billed Tern Gelochelidon nilotica
52. River Tern Steran aurantia
53. Black - Bellied Tern Steran acuticauda
54. Whiskered Tern Chelidonius hybridus
XV. FAMILY : ACCIPITRIDAE
55. Eurasian Marsh Harrier Circus aeruginosus
XVI. FAMILY : PODICIPEDAE
56. Little Grebe Tachybaptus ruficollis
XVII. FAMILY : PHALACROCORACIDAE
57. Little Cormorant Phalacrocorax niger
XVIII. FAMILY : ANHINGIDAE
58. Darter Anhinga melanogaster
XIX. FAMILY : ARDEIDAE
59. Little Egret Egretta garzetta
60. Western Reef Heron Egretta gularis
61. Grey Heron Ardea cinerea
62. Purple Heron Ardea purpurea
63. Great Egret Casmerodius albus
178 A. Waterfowl recorded during Phase-I (September 1999-March 2000) :
64. Intermediate Egret Mesophoyx intermedia
65. Cattle Egret Bubulcus grayii
66. Indian Pond Heron Ardeola grayii
67. Little Heron Butorides striatus
68. Black -crowned Night Heron Nycticorax nycticorax
XX. FAMILY : PHOENICOPTERIDAE
69. Greater Flamingo Phoenicopterus rubber
XXI. FAMILY : THRESKIORNITHIDAE
70. Glossy Ibis Plegadis falcinellus
71. Black - Headed Ibis Threskiornis melanocephalus
72. Black – Ibis Pseudibis papillosa
73. Eurasian Spoonbill Platalea leucorodia
XXII. FAMILY : PELECANDIAE
74. Great White Pelican Pelecanus onocrotalus
XXIII. FAMILY : CICONIIDAE
75. Painted Storck Mycteria leucocephala
76. Asian Openbill Anastomus oscitans
77. Woolly - Necked Stork Ciconia episcopus
78. White Stork Ciconia ciconia
XXIV. FAMILY : PASSERIDAE
79. White Wagtail Motacilla alba
80. Yellow Wagtail Motacilla flava
179 Additional waterfowl species recorded at TS during Phase - II (August 2000-March 2001)
81. Cotton Pygmy – Goose Nettapus coromandelianus
82. Garganey Anas quequedula
83. Gadwall Anas strepera
84. Purple Swamphen Porphyrio porphyrio
85. Red - necked Phalarope Phalaropus lobutus
86. Oriental Pratincole Glariola maldivarum
87. Little Tern Sterna albifrons
88. Yellow - legged / Huglin's Gull Larus cachinnans / huglinii
89. Great Cormorant Phalacrocorax carbo
90. Dalmatian Pelican Pelecanus crispus
91. Greater Spotted Eagle Aquila clanga
92. Osprey Pandion haliatus
Identification Requiring Further confirmation
1. Black - header Gull Larus ridibundus
2. Indian Cormorant Phalacrocorax fiscicollis
3. Common Snipe Gallinago gallinago
Species recorded at TS in past (not seen during present study)
1. Lesser Flamingo Phoenicopterus minor
2. Great Reed Warbler Acrocephalus arundinaceous
3. White - browed Wagtail Motacilla maderaspatensis
4. Indian Skimmer Rynchops albicollis
5. Black Tern Chlidonias niger
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206