Journal of Threatened Taxa | www.threatenedtaxa.org | 26 October 2018 | 10(11): 12464–12488

 

 

The composition and status of waterbirds of Perur Lake in Tamil Nadu, India

 

G. Parameswaran 1 & R. Sivashankar 2

 

1 438/11, Mayflower Apartments, 130, Vivekananda Road, Ramnagar, Coimbatore, Tamil Nadu 641009, India

2 110, Ramasamy Layout 1st cut, Ellai Thottam Road, Peelamedu, Coimbatore, Tamil Nadu 641004, India

1 shivanparam@gmail.com (corresponding author), 2 sivas754@gmail.com

 

 

 

Abstract: The composition and status of waterbirds in Perur-Sundakamuthur Lake, a wetland in Coimbatore, Tamil Nadu, was studied from May 2014 to April 2016. This wetland is home to resident and local migrant birds throughout the year and is also used by winter migrant birds during a part of the year (September to March). From the data collected so far, the highest number of birds and species diversity was recorded from February to April. It is, therefore, imperative to maintain adequate water levels in these wetlands during these crucial months for the benefit of the northward migrating waterbirds. During the study period, it was also found that activities like road building could have had a deleterious effect on the number of birds that used this wetland. We recommend that similar studies be carried out in some of the adjoining wetlands of the area in a synchronous manner to further understand the subtlety of local avian movements within the greater Coimbatore area.

 

Keywords: Birds, Coimbatore, diversity, Perur-Sundakamuthur Lake, waterbirds, water level, wetland.

 

 

 

doi: http://doi.org/10.11609/jott.3864.10.11.12464-12488   |  ZooBank: urn:lsid:zoobank.org:pub:FEE66370-FDBE-49C7-BB51-1BB7B6CFDAA7

 

Editor: Anonymity requested. Date of publication: 26 October 2018 (online & print)

 

Manuscript details: Ms # 3864 | Received 28 October 2017 | Final received 01 July 2018 | Finally accepted 17 October 2018

 

Citation: Parameswaran, G. & R. Sivashankar  (2018). The composition and status of waterbirds of Perur Lake in Tamil Nadu, India. Journal of Threatened Taxa 10(11): 12464–12488; http://doi.org/10.11609/jott.3864.10.11.12464-12488

 

Copyright: © Parameswaran & Sivashankar 2018. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use of this article in any medium, reproduction and distribution by providing adequate credit to the authors and the source of publication.

 

Funding: None.

 

Competing interests: The authors declare no competing interests.

 

Author Details: G. Parameswaran is an engineering graduate from PSG College of Technology, Coimbatore, India. He was employed in USA for nearly three decades, mostly in the field of logistics. His interest in birds led him into being a conservation activist and also one of the Board of Directors of Seattle Audubon Society, USA (2003–08). In that capacity he qualified himself as a Master-birder and led many field trips and bird surveys in Washington State. He is currently retired and lives in his home town of Coimbatore, where he is pursuing his passion of bird watching and learning Sanskrit.  R. Sivashankar is an engineering graduate from Karpagam College of Engineering. He is currently employed as a Junior Manager at ROOTS INDUSTRIES INDIA LIMITED, an automotive ancillary. He is an active bird watcher and nature enthusiast, who contributes to systematic surveys in and around Coimbatore region. His interests include ecosystem conservation through citizen science activities and systematic data collection to understand avian movements.

 

Author Contribution: Both the authors contributed equally. GP - contributing more on the subject side and RS contributing more on the computer related matters like data entry, formatting etc.

 

Acknowledgements: We thank R. Vridhi, Dilip Joshi, Sai Vivek, and Gajamohanraj for their continuous support and association to this bird count. We thank Chetankumar Joshi, Saravanan Natrayan, G. Prakash, P. Mohanprasath, Sarayu Ramakrishnan, Kavya Ram, and Sharang Satish for their assistance in bird count and bird identification at different stages of this study. We would also like to show our gratitude to Sanjay Molur (Zoo Outreach Organization & Wildlife Information Liaison Development), Payal B. Molur (conservation education consultant), Priyanka Iyer, and Keerthi Krutha for their insight and expertise in understanding the ecology of wetlands.

 

 

 

INTRODUCTION

 

Birds occupy a range of habitats and are responsive and sensitive to environmental changes. Wetlands are one of the most productive ecosystems and waterbirds play a vital role in its effective functioning. Urban habitats that include wetlands are continuously disturbed by development activities, which affect bird populations (Raju 2015). Although most urban wetlands in India are considered to be extremely polluted, they still attract a large number of winged visitors (Reginald et al. 2007). Our conclusions are based on the compilation and interpretation of data gathered during monthly bird counts in Perur-Sundakamuthur Lake from May 2014 to April 2016.

 

 

STUDY AREA

 

This study was carried out in Perur-Sundakamuthur Lake (Perur Lake henceforth) (10.968 N & 76.928 E), a wetland complex located in the urban fringe of metropolitan Coimbatore, Tamil Nadu. According to Pragatheesh & Jain (2013), the wetland complex in Coimbatore consisting of around 30 lakes was constructed during the Kongu-Chola regimes in 8th and 9th Century AD in the vicinity of the Noyyal River basin. Considering the nature of the river to flood downstream near Noyyal villages and to exploit the scanty rainfall typical of this region, the Kongu-Chola kings channelized the fury of the monsoon by creating a system of lakes and anicuts to aid the recharging of groundwater. Over a period of time, these wetlands came to house a lot of species of birds, fish, and other forms of life. Thus, the wetlands in this dry region not only provide the much-needed water for agriculture but also perform functions such as flood control, groundwater recharge, water purification, nutrient retention, and biodiversity conservation.

The Perur Lake, which has a catchment area of 5.768km2, is fed by Kuniyamuthur anicut channel from Noyyal River as an overflow of excess water from Ganganarayanasamudhram Lake, located further upstream. The length of the road that adjoins the Perur Lake on the eastern side is approximately 2km (formerly a mere bund), which is shaped like a crescent and filled with partial vegetation on one side and residential areas on the other. Given the lack of industrial activity in the area and non-flow of sewer into this lake, it is relatively unpolluted and contains a rich diversity of molluscs and fish that provide food for waterbirds. According to Wetland (Conservation and Management) Rules, 2010, the violations in this lake are encroachment and road construction as presented in Table 3 (Pragatheesh & Jain 2013).

 

Size of the wetland

Catchment area: 5.768km2

Water spread area: 1.072km2

Capacity: 1,470,777m3 (51.94 m.cft)

Full tank level: 4.51m

Maximum water level: 5.12m

Top bund level: 6.49m

Depth: 4.511m

Length of the bund: 1,350.00m

Length of shoreline: unknown

Anicut: 3.5Sq.km

 

Inlets and outlets

It receives excess water from the Ganganarayanasamudharam Lake.

Number of inlets: 1 (channel)

Number of outlets: 7 (one weir & six sluices)

Length of surplus escape: 35.67m

 

 

MATERIALS AND METHODS

 

The field observations of birds were carried out from May 2014 to April 2016. The periodicity of the survey was once a month, which usually fell on the second Saturdays. A systematic count of birds that were seen and heard was recorded in a checklist by walking along the 2km road in the mornings. The equipment that was used included binoculars (Nikon 10x42.5, Zeiss 10x42 & Eagle optics 10x42) and a spotting scope (Bausch & Lomb 20–80x magnification). In addition, cameras were also used when necessary during the count. The number of people who participated in the count on any given day varied from three to eight.

The identification of birds was carried out with the help of field guides (Grimmet et al. 2011; Paulson 2005; Rasmussen & Anderton 2012). The checklist was prepared using standardized common and scientific names after Grimmet et al. (2011). The status of birds was categorized as resident, local migrant, winter migrant, and vagrant and are defined as follows. It should be added that some species like Lesser Whistling-duck Dendrocygna javanica and Little Ringed Plover Charadrius dubius have dual status due to their migrant and resident populations.

Resident (R) – A species that stays and breeds in the area throughout the year or most of the year (e.g.: Spot-billed Duck Anas poecilorhyncha).

Local migrant (LM) – A species that stays in an area throughout the year or most of the year whose adult population moves outside the area to breed (e.g.: Painted Stork Mycteria leucocephala).

Winter migrant (WM) – A species that spends its non-breeding winter months (mostly from September to April) in the area (e.g.: Wood Sandpiper Tringa glareola).

Vagrant (V) – A species that occasionally visits an area and whose pattern cannot be discerned (e.g.: Woolly-necked Stork Ciconia episcopus).

 

 

RESULTS

 

The bird species recorded in Perur Lake during this period were 112, belonging to 44 families and 18 orders. Since this study focuses exclusively on waterbirds, which are 49 in number belonging to 14 families and seven orders, only their status is discussed in detail and listed in Table 1.

 

 

Table 1. Waterbirds of Perur Lake, Coimbatore, Tamil Nadu

 

 

Common name

Scientific name

Status

Observed months

 

Anseriformes: Anatidae

 

 

1

Lesser Whistling-duck

Dendrocygna javanica

R/ LM

YR except for Apr & Jun

2

Cotton Pygmy-goose

Nettapus coromandelianus

LM

Nov–Jan

3

Indian Spot-billed Duck

Anas poecilorhyncha

R

YR

4

Northern Shoveler

A. clypeata

WM

Oct–Mar

5

Northern Pintail

A. acuta

WM

Dec– Mar

6

Garganey

A. querquedula

WM

Aug–Apr

7

Common Teal

A. crecca

WM

Oct, Jan, Feb

 

Podicipediformes: Podicipedidae

 

 

8

Little Grebe

Tachybaptus ruficollis

R

YR except for May, Jun

 

Ciconiiformes: Ciconiidae

 

 

9

Asian Openbill

Anastomus oscitans

LM

YR

10

Woolly-necked Stork

Ciconia episcopus

V

Mar, Apr

11

Painted Stork

Mycteria leucocephala

LM

Feb–May, Jul, Sep–Dec

 

Suliformes: Phalacrocoracidae

 

 

12

Indian Cormorant

Phalacrocorax fuscicollis

R

YR except for May, Jun

13

Great Cormorant

P. carbo

LM

Dec, Jan

14

Little Cormorant

P. niger

R

YR

 

Suliformes: Anhingidae

 

 

15

Oriental Darter

Anhinga melanogaster

R

YR

 

Pelecaniformes: Pelecanidae

 

 

16

Spot-billed Pelican

Pelecanus philippensis

LM

Jul, Sep, Oct

 

Pelecaniformes: Ardeidae

 

 

17

Yellow Bittern

Ixobrychus sinensis

LM

Feb–Apr

18

Cinnamon Bittern

I. cinnamomeus

LM

Feb, Apr

19

Grey Heron

Ardea cinerea

R

YR

20

Purple Heron

A. purpurea

R

YR

21

Great Egret

Casmerodius albus

LM

YR

22

Intermediate Egret

Mesophoyx intermedia

LM

YR

23

Little Egret

Egretta garzetta

LM

YR

24

Western Reef-Heron

E. gularis

V

O (Mar)

25

Cattle Egret

Bubulcus ibis

R

YR

26

Indian Pond-Heron

Ardeola grayii

R

YR

27

Striated Heron

Butorides striata

R

Mar, Apr, Jun–Aug

28

Black-crowned Night-Heron

Nycticorax nycticorax

R

Feb–Apr, Jul–Sep, Nov

 

Pelecaniformes: Threskiornithidae

 

 

29

Glossy Ibis

Plegadis falcinellus

WM

Sep–Mar

30

Black-headed Ibis

Threskiornis melanocephalus

LM

Mar–May, Aug, Sep

31

Eurasian Spoonbill

Platalea leucorodia

LM

O (Oct)

 

Gruiformes: Rallidae 

32

White-breasted Waterhen

Amaurornis phoenicurus

R

YR except for Jun

33

Grey-headed Swamphen

Porphyrio porphyrio

R

YR

34

Common Moorhen

Gallinula chloropus

R

YR except for Jun, Jul

35

Eurasian Coot

Fulica atra

R

YR

 

Charadriiformes: Recurvirostridae

 

 

36

Black-winged Stilt

Himantopus himantopus

WM

Feb–May, Nov

 

Charadriiformes: Charadriidae

 

 

37

Red-wattled Lapwing

Vanellus indicus

R

YR

38

Little Ringed Plover

Charadrius dubius

WM/ R

Feb–Jun, Sep, Oct

 

Charadriiformes: Jacanidae

 

 

39

Pheasant-tailed Jacana

Hydrophasianus chirurgus

LM

Sep, Oct, Dec, Jan

40

Bronze-winged Jacana

Metopidius indicus

LM

Aug, Jan

 

Charadriiformes: Scolopacidae

 

 

41

Common Sandpiper

Actitis hypoleucos

WM

Aug–Apr

42

Green Sandpiper

Tringa ochropus

WM

Nov, Jan–Apr

43

Common Greenshank

T. nebularia

WM

Oct, Feb–Apr

44

Marsh Sandpiper

T. stagnatilis

WM

Feb–Apr

45

Wood Sandpiper

T. glareola

WM

Sep–Nov, Feb–Apr

46

Temminck's Stint

Calidris temminckii

WM

Feb, Mar

47

Little Stint

C. minuta

WM

Oct, Feb–Apr

 

Charadriiformes: Laridae

 

 

48

Whiskered Tern

Chlidonias hybrid

WM

Sep, Jan–Mar

49

River Tern

Sterna aurantia

WM

Nov, Jan

 

R - resident, LM - local migrant, WM - winter migrant, V - vagrant,

YR - year-round (recorded throughout the year), O - recorded only once

 

 

Anseriformes: Anatidae

Lesser Whistling-duck Dendrocygna javanica is a species that has the potential to breed in this area when conditions are favourable and to not do so when they are not. Therefore, it has the dual status of a possible resident or a local migrant, based on local factors like water levels in the wetland (Ali 2002). This species was recorded throughout the year except during the dry months from April to June (the only exception being that in May 2015 when five birds were recorded due to favourable water conditions). The highest numbers of this species were seen during the winter months of January 2015 and February and March 2016 when 97, 159, and 74 species were recorded, respectively. Based on these observations, this possible breeder in the area during the southwestern monsoon months (Rasmussen & Anderton 2012) is primarily a local migrant during winters in Perur Lake (Fig. 1).

Cotton Pygmy-goose Nettapus coromandelianus is a local migrant duck in the area that was recorded only during winter months in an erratic manner. They were sighted from November 2014 to January 2015; a single individual was sighted in December 2015 (Fig. 2).

Indian Spot-billed Duck Anas poecilorhyncha is a resident species that was recorded every month since the count began in March 2014. Its highest counts were recorded during the migratory months of September and October during autumn and also in February, March, and April during spring. In September and October 2014, however, its numbers were depressed due to very high water levels, which were devoid of shoreline exposure. This dabbling duck favours shallow freshwater lakes with extensive emergent vegetation (Madge & Burn 1988) and shoreline exposure. This characteristic helps to explain its low numbers in September and October of 2014, which were 14 and 22. During similar periods in 2015, however, the numbers of this species were 227 and 114, respectively, due to favourable conditions (Fig. 3). In January 2015, a pair was observed in courtship behaviour, which terminated in copulation. In the October 2015 bird count, when 114 individuals of this species was recorded, an adult bird with a crèche of five chicks was also observed, confirming the breeding status of this bird in this lake.

Northern Shoveler Anas clypeata is a winter migrant species (Fig. 4a) that was recorded during the winter months between December 2014 and March 2015. The numbers were 113, 140, 131, and 99 in each month of this period. Due to some inexplicable reason, three and nine individuals of this species were recorded only in October 2015 and February 2016, respectively, of the second season.

Northern Pintail Anas acuta is also a winter migrant duck (Fig. 5a) that was recorded from December 2014 to March 2015, whose numbers were 71, 218, 436, and 30, respectively. Similar to Northern Shoveler, the Pintails were also reduced in numbers during the subsequent year; only two and 14 individuals were recorded in January and February 2016, respectively.

Garganey Anas querquedula, according to our records for Perur Lake, is the most numerous winter migrant duck (Figs. 6a,b). It was recorded every month from December 2014 to April 2015, with peak sightings in February and March 2015, which were 532 and 436, respectively. Its sightings, however, dwindled during the winter months of 2015–2016 as only 21 and 152 individuals were recorded in February and March 2016, respectively. Note: Species 4, 5 & 6 that are winter migrant ducks were recorded in lesser numbers in 2015–2016 when compared with similar months in 2014–2015. Only continued monitoring can possibly reveal the reasons behind these annual variations.

Common Teal Anas crecca is a winter migrant species with erratic presence in the lake. The species was recorded in January and February 2015 and a pair was observed in October 2015 (Figs. 7a,b).

 

 

 

 

 

Podicipediformes: Podicipedidae

Little Grebe Tachybaptus ruficollis is a resident species recorded throughout the year, except in the months of May and June. This bird is extremely water dependent and rarely leaves the water (Rasmussen & Anderton 2012). Accordingly, its highest counts were recorded during the months when the water level was high, such as 33 in September 2014, 50 and 29 in January and February 2015, respectively (Fig. 8). The breeding season of this species ranges principally between April and October (Ali 2002). This species could probably breed in this lake when water levels are medium to full, which occurs usually after the arrival of the southwestern monsoon. Its breeding status was confirmed in the lake when a flock with three chicks was observed in September 2014. This is evidence of post-breeding dispersal when they were recorded in low numbers from September onwards; however, only future observations can verify this behaviour.

 

Ciconiiformes: Ciconiidae

Asian Openbill Anastomus oscitans is a local migrant stork that breeds in southern India mostly from November to March (Ali 2002). This bird was consistently recorded in Perur Lake from May to July 2014 and again from January to June 2015, with a brief presence in September and October 2015 and then being sighted in sufficient numbers from March 2016 onwards. This pattern indicates that the breeding adults migrate out of the area during its breeding season, which could vary from September to March. High water levels with unexposed shoreline are a deterrent to its presence, as indicated by the full water levels from August to December 2014 when very few individuals of the species were recorded. In contrast, in September and October 2015, when water levels were less than full with some shoreline exposure, 24 and 17 individuals of this species were recorded, respectively (Fig. 9). Exposed shoreline makes prey-finding possible for this species. Subsequently, when water levels became higher from November 2015 onwards, very few numbers of this species were sighted. This species, however, started to return during the winter months after the full water level receded to expose the shoreline and gradually increased in numbers as the lake dried out.

Woolly-necked Stork Ciconia episcopus is a vagrant in Perur Lake and was sighted twice in our count period when three and one individuals were recorded in March 2015 and April 2016, respectively. In addition, Sharang (2016) also reported a flock of 62 birds of this stork species on 29 March 2016 from this lake (Fig. 10). These observations, even though scanty in nature, probably indicate that this species might be using Perur Lake as a transit point during spring migration only. A small population of Woolly-necked Stork breeds in the neighbouring districts of Kerala (Sashikumar et al. 2011).

Painted Stork Mycteria leucocephala is another local migrant species that breeds in southern India between August and January, varying with local conditions (Ali 2002; Rasmussen & Anderton 2012). This species was observed in the lake only when the water was present in levels that were conducive to prey-finding. Its highest counts were recorded in September and October 2015 and in April 2016 when 30, 34, and 35 individuals were sighted, respectively (Fig. 11), when the water level was between shallow and medium, which made prey-finding possible. In the study area, it was present mostly from September to May. This species is listed as Near Threatened due to its moderate population reduction owing to hunting, drainage, and pollution (Rahmani 2012).

 

Suliformes: Phalacrocoracidae

Indian Cormorant Phalacrocorax fuscicollis is a resident cormorant species and its presence is sparse in Perur Lake. This species was observed in all months of the year except during the summer months of May, June, and July 2014 and from March to June 2015. The highest number was recorded in February 2016 when 11 individuals of this species were sighted. Its absence in October 2014 even when the water level was full shows the erratic presence of this species in Perur Lake. This species probably breeds in the area in other water bodies.

Great Cormorant Phalacrocorax carbo is a local migrant cormorant species that was sighted twice during our count period, in December 2015 and January 2016. In both the occurrences, only a single bird was recorded (Fig. 13).

Little Cormorant Phalacrocorax niger is a resident cormorant species that was recorded every month since the count began in March 2014. Its highest counts were recorded in the winter months of January and February 2015 when 252 and 203 individuals were sighted, respectively (Fig. 14). The population of this species drastically reduced when the water levels were low, especially during the summer months from April to July. This species could be a possible breeder in this lake when conditions are favourable. The breeding season of this bird in southern India chiefly lies between November and February (Ali 2002).

 

 

 

 

 

 

 

Suliformes: Anhingidae

Oriental Darter Anhinga melanogaster is a resident species that was recorded year-round except in May & September 2014 and March & April 2016. Its highest counts were recorded in November and December 2014 and in September 2015 when 22, 24, and 23 individuals of this species were sighted, respectively. This species is listed as Near Threatened because of its moderate population reduction due to pollution, drainage, hunting, and collection of eggs and nestlings (Rahmani 2012).

 

Pelecaniformes: Pelecanidae

Spot-billed Pelican Pelecanus philippensis is a local migrant species and its sighting in Perur Lake is sparse. This species was recorded in September and October of 2014 and 2015; a single member was recorded in July 2015. Its highest count was recorded in September 2015 when 25 numbers of this species were sighted. Notably, the presence of this species was observed in the lake when water levels were above medium. In 2001, Bird Life International listed this species as Vulnerable. Increased protection, however, enabled a recovery in numbers of this species and it was downlisted from Vulnerable to Near Threatened in 2007 (Rahmani 2012)

 

Pelecaniformes: Ardeidae

Bitterns, as a group, are uncommon in Perur Lake and their secretive nature resulted in infrequent sightings.

Yellow Bittern Ixobrychus sinensis &

Cinnamon Bittern Ixobrychus cinnamomeus are the two species of local migrant (LM) bitterns recorded in Perur Lake. Yellow Bittern was recorded in February, March & April 2015 and March 2016 and their numbers were three, two, two, and one, respectively (Fig. 17). Cinnamon Bittern was recorded in February 2015 and April 2016; in both occurrences, a single bird was sighted (Fig. 18). These are possibly local migrants that are sparsely recorded in the lake during winter months.

Grey Heron Ardea cinerea is a resident species that was recorded year-round in Perur Lake. Its highest counts were recorded in September and October 2015 when 46 and 21 individuals were sighted, respectively, when the water conditions were probably favourable. Their habitat preferences are brackish water, wetlands, reedbeds, and paddy fields (Rasmussen & Anderton 2012). Its breeding season in southern India ranges from November to March (Ali 2002). It is probable that in September and October this species might be using this lake as a transit point (Fig. 19).

Purple Heron Ardea purpurea is a resident species that was recorded year-round except in May 2014 and July 2015. Its highest counts were recorded in April 2015 and February 2016 when nine and 11 individuals of this species were sighted, respectively. Its breeding season in India ranges from June to March depending on locality (Ali 2002), and in neighbouring Kerala, it reportedly breeds in July and August (Sashikumar et al. 2011).

Great Egret Casmerodius albus is a local migrant species in the lake. It was recorded year-round in Perur Lake except from August to October 2014, July 2015, and December 2015. They were usually sighted in numbers ranging from one to eight in this lake; however, the highest count was recorded in April 2016 when 31 individuals of this species were sighted (Fig. 21). This observation shows that this species might be using Perur Lake as a transit point during spring migration.

Intermediate Egret Mesophoyx intermedia is a local migrant species in the lake. It was recorded year-round in the lake, except for the dry months of May and June 2014 and the months from September to November 2014 when the water level was full. Its highest count was recorded in April 2016 and December 2015 when 24 and 17 individuals of the species were sighted, respectively.

Little Egret Egretta garzetta is another local migrant species in the lake that was recorded year-round. The highest counts of this species were recorded in the spring migration period of March and April 2015 and April 2016 when 60, 116, and 215 individuals were sighted, respectively (Fig. 23).

Note: In analysing the numbers of the three white egret species, namely Great, Intermediate, and Little, it can be deduced that these species probably use Perur Lake as a transit point mostly during the months of March and April. This can be clearly seen in the respective figures (Figs. 21, 22 & 23) when their numbers are at the highest levels.

Western Reef-Heron Egretta gularis is a vagrant species in the area. This bird was recorded once in Perur Lake when a sole bird was sighted in March 2015 (Fig. 24).

Cattle Egret Bubulcus ibis is a resident species that was recorded year-round in the lake. The highest counts of this species were recorded in November 2014 and April 2015 when 37 and 40 individuals of this species were sighted, respectively (Fig. 25). Birds with breeding plumage were observed during its breeding months of November to March; however, no nests were recorded in the vicinity of the lake. It builds untidy stick nests in mixed colonies with Cormorants and Pond Herons, often in the vicinity of little villages (Ali 2002).

Indian Pond Heron Ardeola grayii is a resident that was recorded year-round in the lake. Its highest counts were recorded in January 2015 and April 2016 when 65 and 64 of this species were sighted, respectively (Fig. 26). According to Ali (2002), its breeding season in southern India is from November to January and its nesting behaviour is similar to that of Cattle Egret. We, however, sighted some birds of this species displaying its breeding plumage in April and May 2015 though no nests were recorded in the vicinity of the lake. Its presence is higher in winter and also during spring migration, indicating that some of them might be using this lake as a transit point.

Striated Heron Butorides striata is a resident species in our area that was recorded in the months of August 2014, March 2015, June to August 2015, and April 2016. The highest count of this species was recorded in April 2016, when four birds were sighted. Even though a resident breeder, it was unrecorded for many months during our count (Fig. 27), due to its secretive and crepuscular behaviour. Occasionally, however, it may be also active during the daytime, particularly in cloudy overcast weather. Its breeding season is from March to August with local variations (Ali 2002). In April 2016, a single bird in breeding plumage was observed in this lake.

Black-crowned Night-Heron Nycticorax nycticorax is a resident species and its presence is sparse in Perur Lake. Its highest count was recorded in February 2016 when 18 individuals of this species were sighted flying overhead (Fig. 28). Most of them were immature or juvenile birds, indicating its possible breeding in the area. This species, however, is largely unrecorded during our counting sessions due to its nocturnal and crepuscular nature similar to that of the Striated Heron. According to (Ali 2002), this species breeds from December to February in southern India.

 

 

 

 

 

 

Pelecaniformes: Threskiornithidae

Glossy Ibis Plegadis falcinellus is a winter migrant species that was recorded in the lake during the winter months from September to March. The highest counts were recorded in September and October of 2015 when 53 and 68 of this species were sighted, respectively. During September and October of 2014, however, this species was not recorded in the lake. A plausible explanation can be arrived at by analysing its sight recordings in conjunction with the water level variations. When water levels were shallow with shoreline exposure that facilitated prey-finding, this species was recorded in large numbers as was the case in September and October 2015. When water levels were full in September and October of 2014, however, they were absent. This fact can be clearly seen in Fig. 29b where the water level was medium and its numbers were higher.

Black-headed Ibis Threskiornis melanocephalus is a local migrant species that was recorded erratically in the lake. The highest count was recorded in April 2016 when six of this species were sighted. According to (Ali 2002), its nesting season is largely “ill-defined” and it may nest in southern India from November to December. This species was unrecorded in the lake during those months. According to Rahmani (2012), this species is nomadic and migratory in nature depending upon the availability of water. Since its population reduction in Asia due to an entire gamut of threats from hunting, disturbances at the breeding colonies to drainage, and conversion of foraging habitats to agriculture lands, it is listed as Near Threatened.

Eurasian Spoonbill Platalea leucorodia is a local migrant species that was recorded only once in October 2015 when 11 individuals of the species were sighted. It is not possible to conduct an analysis based on this single observation.

 

Gruiformes: Rallidae

White-breasted Waterhen Amaurornis phoenicurus is a resident species that was recorded year-round except during the drier months in the lake from May to July. Its highest count was recorded in February 2015 when six individuals of this species were sighted (Fig. 32). Its breeding season is from June to October or during southwestern monsoon (Ali 2002).

Grey-headed Swamphen Porphyrio porphyrio is a resident species that was recorded year-round in Perur Lake. The highest counts of this species were recorded in February and March of 2015 and 2016 when 48, 25, 44, and 74 individuals were sighted, respectively. In addition, in April 2016, 27 birds were sighted, possibly indicating its larger counts during spring migration. In the lake, this species is mostly recorded when water is present and its highest counts are recorded when the water levels vary between low and medium. Its breeding season is during the monsoon months of June to September (Ali 2002). During the March 2016 count, however, when the highest number of this species was recorded, three chicks were sighted accompanying an adult indicating its possible breeding status.

Common Moorhen Gallinula chloropus is a resident species that was recorded year-round, except in June and July in the lake. Its breeding season is from June to September or during the southwestern monsoon (Ali 2002). The highest counts were recorded in January and April of 2015 when 25 and 30 individuals of this species were sighted, respectively.

Eurasian Coot Fulica atra is a resident species that was recorded year-round in the lake except for the months of July 2014, June 2015, and April 2016. From August 2014 to February 2015, the range of variation of this species sighted was from 68 to 584, when the highest counts occurred between September and October 2014 and also during the winter months of January and February 2015. The plausible reasons behind such an occurrence could be the fact that the combination of local migrant birds, as well as locally breeding birds, could have been sighted simultaneously, especially in September and October 2014 when the counts were 575 and 584, respectively. It is worth noting that during this period, the water levels were favourable for breeding, which ranged from medium to full. During a similar period in 2015-2016, however, its numbers were significantly reduced due to unfavourable water levels. Even though Ali (2002) states that Eurasian Coots breed during the monsoonal months of July and August, according to Rasmussen & Anderton (2012), this species could possibly breed in southern India up to November. A juvenile bird and a nest of grassy vegetation were recorded during our November 2014 count. Additionally, a single chick was observed in March 2016. These observations confirm its breeding status in the lake when conditions are favourable.

 

 

 

 

 

 

Charadriiformes: Recurvirostridae

Black-winged Stilt Himantopus himantopus is a winter migrant species that was recorded in the lake in a sporadic manner when water levels were less than full with adequate shallow water and shoreline exposure. The highest counts were recorded in March 2015 and 2016 when 26 and 56 of this species were sighted, respectively. During these months, water levels were medium and facilitated prey–finding. Its long stilt-like legs, when compared with other waders, enable it to find prey by walking further in the water (Ali 2002).

 

Charadriiformes: Charadriidae

Red-wattled Lapwing Vanellus indicus is a resident species that was recorded year-round, except in May and June 2014 when the water level was very low and January of 2015 and 2016 when the water level was high. Its highest count was recorded in September and October of 2015 when 15 and 16 individuals were sighted, respectively. Its breeding season is chiefly from March to August (Ali 2002). A juvenile of this species was observed in July 2015

Little Ringed Plover Charadrius dubius has two subspecies that are called C.d.curonicus, which is entirely a winter migrant in India, and C.d.jerdoni, a possible breeder and resident (Hayman et al. 1986). This species was recorded in February and March of 2015 and 2016 and in May, June, September and October 2015. Its highest counts were recorded in March 2015 and 2016 when 84 and 39 individuals of this species were sighted, respectively, during the spring migration season when water levels were favourable and there was adequate shoreline exposure. An overwhelming majority of the birds sighted during these months are the migratory form C.d. curonicus. When conditions are favourable, the resident subspecies C.d. jerdoni could be a possible breeder in this lake. In May and June 2015, three and one individuals of this subspecies were recorded, respectively. Due to changing water levels, however, its nesting could not be confirmed.

 

Charadriiformes: Jacanidae

Pheasant-tailed Jacana Hydrophasianus chirurgus is a local migrant species that was infrequently recorded in the lake. Its numbers when sighted were very few such as one, one, and two in September, October, and December 2014, respectively; however, 17 individuals of the species were sighted in January 2015, which is an inexplicable anomaly. It is not been recorded in the lake since then.

Bronze-winged Jacana Metopidius indicus is a local migrant species that is infrequently recorded in the lake, similar to Pheasant-tailed Jacana. A single individual of this species was sighted in January and August 2015.

 

Charadriiformes: Scolopacidae

Common Sandpiper Actitis hypoleucos is a winter migrant species that was recorded from August to April. Its highest count was recorded in March 2015 when 21 individuals of this species were sighted. According to Ali (2002), it is one of the earliest wader migrants to arrive (August) and also one of the last to leave (May). The sightings of this species in this lake match this statement to a large extent.

Green Sandpiper Tringa ochropus is a winter migrant species that was recorded during the period of January to March of 2015 and 2016 and additionally in November 2014 and April 2016. The highest counts were five and six recorded in February 2015 and March 2016, respectively, during the spring migration season.

Common Greenshank Tringa nebularia is a winter migrant species that was recorded in February–April 2015, October 2015, and March & April 2016 in the lake when the water levels were favourable with adequate shoreline exposure. This pattern usually happens during the spring migration months from February to April. Its highest counts were recorded in February to April 2015 and April 2016, when seven, six, and 14 of this species were sighted, respectively.

Marsh Sandpiper Tringa stagnatilis is a winter migrant species that was sighted sparsely in the lake. Most of the sightings were during the spring migration months of February and March 2015 and March 2016 when three individuals were sighted on each occasion.

Wood Sandpiper Tringa glareola is the most numerous winter migrant sandpiper species in the lake. Even though it was recorded from September to April, it is primarily a species that is sighted during the spring migration months from February to April. Its highest counts during this season were in March 2015 and 2016 when 62 and 100 individuals were sighted, respectively. When water level conditions are favourable with shoreline exposure, as was the case in October 2015, 86 individuals of this species were recorded.

Temminck’s Stint Calidris temminckii is a winter migrant species that was recorded only twice in the lake during the count period of February and March 2015 when four and eight of this species were sighted, respectively; this correlates with the spring migration season.

Little Stint Calidris minuta is a winter migrant species that was recorded primarily during the spring migration months of February & March 2015 and March 2016. Its highest counts were recorded in March 2015 and 2016 when 49 and 22 of this species were sighted, respectively.

 

Charadriiformes: Laridae

Whiskered Tern Chlidonias hybrid is a winter migrant species that was recorded sporadically in September 2014, January–March 2015, and January 2016. Its highest counts of 40 and 38 were recorded in September 2014 and January 2016, respectively, when the water level was high.

River Tern Sterna aurantia is a winter migrant species that was recorded only twice in the lake when a single bird in November 2014 and a couple in January 2016 were sighted. The water levels of the lake during both the sightings were full.

 

 

 

 

 

 

 

 

Table 2. Description of water level

 

Water level

Description

Dry

The absence of water in the lake or the presence of a negligible amount of wetness

Low

The presence of a small amount of water in a few isolated puddles

Medium

The presence of water in the whole lake with shoreline exposure in the periphery

Full

Lake completely filled with water without any shoreline exposure

 

 

Table 3. Types of encroachments in Perur Lake (Pragatheesh & Jain 2013)

 

Type of encroachment

Authority

Violation of wetland rules

 

Hutments

Private

Section 4(1)(vi)

Hutments located in the land-filled areas.

Agriculture

Private

Section 4(2)(x)

 

Dumping of waste

 

Section 4(1)(iv)

Dumping debris and domestic solid waste along the bund.

Roads

 

Section 4(1)(vi)

Kovai-Puthur bypass road on the eastern side on the lake & a metal road connecting SH-164 with Kovai-Puthur bypass road on the northern bund.

 

 

 

Types of Encroachments

Waterbirds usually avoid areas with extensive disturbance, choose roosting or foraging sites with fewer disturbances, and generally prefer wetlands with features that maximise the abundance and accessibility of their food (Khan et al. 2016). The types of habitat encroachments in Perur Lake that impair its functionality are road construction and its use for motor vehicles, illegal and unauthorised dumping of waste material, conversion to an artificial reservoir for agricultural use, and establishment of hutments.

For instance, road construction was carried out on the eastern bund of the Perur Lake covering the entire eastern border of 2km for use by motor vehicles. The probable effect of road construction on bird population and species diversity can be interpreted from the graphs given below. The road building activity appears to have reduced the sightings of the number and diversity of birds during the construction period, which lasted from March to August 2014.

 

 

DISCUSSION

 

From the analysis of the data collected from May 2014 to April 2016, it is clear that it is the resident/ local migrant birds that utilise this wetland throughout the year (Figs. 50–53).  In addition, this wetland complex is also home to at least 17 species of winter migrant birds. Relations between habitat characteristics and waterbird abundances are often difficult to interpret as different factors act simultaneously, confounding the effects of individual ones, as birds frequent wetlands not only for food but also for rest and shelter. Migratory waterbirds are, however, opportunistic and adapt to utilise various habitat types during migration and colonisation (Khan et al. 2016).

 

Our conclusions from the observations can be stated as follows:

As far as Perur Lake is concerned, the presence or absence of water and its levels is a key determining factor of the avian species composition, the details of which are discussed in the individual species accounts.

It appears from the data collected so far that the bird species diversity and actual numbers are at their highest (Figs. 51, 52 & 53) during the months of February, March, and April, thus possibly pointing towards the highest avian diversity and numbers during their northward migration in spring.

A mere two years’ set of data, however, is simply insufficient to substantiate this possible pattern. Nevertheless, it behoves us to maintain adequate water levels in these wetlands for all birds, especially for migrant birds, during the critical months of March, April, and May. Local communities too might derive benefits from this practice as it allows more time and opportunity for groundwater recharge.

Finally, looking at the larger picture, it is extremely important that similar studies be conducted in some of the adjoining wetlands of the area in a synchronous manner. Only an analysis of such a comprehensive collection of data can provide a better understanding of the subtlety of avian movements and their population in the area.

 

 

REFERENCES

 

Ali, S. (2002). The Book of Indian Birds, 13th Revised Edition. Oxford University Press, New Delhi, 326pp.

Grimmet, R., C. Inskipp & T. Inskipp (2011). Birds of the Indian Subcontinent. Oxford University Press, London, 528pp.

Hayman, P., J. Marchant & T. Prater (1986). Shorebirds – An Identification Guide. Houghton Mifflin Company, Boston, 412pp.

Khan, T.N., A. Sinha & P. Hazra (2016). Population trends and community composition of migratory waterbirds in three emerging wetlands of global significance in southwestern Bengal, India. Journal of Threatened Taxa 8(3): 8541–8555; https://doi.org/10.11609/jott.2652.8.3.8541-8555

Madge, S. & H. Burn (1988). Waterfowl: An Identification Guide to the Ducks, Geese and Swans of the World. Houghton Mifflin Company, Boston & New York, 298pp.

Paulson, D. (2005). Shorebirds of North America: The photographic Guide. Christopher Helm, London, 361pp.

Pragatheesh, A. & P. Jain (2013). Environmental degradation of the Coimbatore wetlands in the Noyyal River basin. EIA Resource and Response Centre, Nilgiri, Tamil Nadu, India, 57pp.

Rahmani, A.R. (2012). Threatened Birds of India: Their Conservation Requirements. Indian Birds Conservation Network, Bombay Natural History Society, Royal Society for the Protection of Birds, Oxford University Press, 861pp.

Raju, S. (2015). Population trend of the common birds in a residential area of Thiruvananthapuram City, Kerala. Indian Birds 10(2): 40–45.

Rasmussen, P.C. & J.C. Anderton (2012). Birds of South Asia: The Ripley Guide, Vols. 1 & 2 - 2nd Edition. National Museum of Natural History, Smithsonian Institution & Lynx Edicions, Washington D.C. & Barcelona.

Reginald, J.L., C. Mahendran, S.S. Kumar & P. Pramod (2007). Birds of Singanallur Lake, Coimbatore, Tamil Nadu. Zoo’s Print Journal 22(12): 2944–2948; https://doi.org/10.11609/JoTT.ZPJ.1657.2944-8

Sashikumar, C., J. Praveen, M.J. Palot & P.O. Nameer (2011). Birds of Kerala: Status and Distribution. DC Books, Kottayam, 835pp.

Sharang, S. (2016). eBird checklist S28615320. https://ebird.org/view/checklist/S28615320