Notes on the nesting and foraging behaviours of the Common Coot Fulica atra in the wetlands of Viluppuram District, Tamil Nadu, India

: The nesting and foraging behaviours of the Common Coot Fulica atra were studied in the wetlands of Viluppuram District, Tamil Nadu during the breeding season. A total of 4,054 individuals of Common Coot including 467 juveniles and 1,327 nests were enumerated. Of the 1,327 nests, 1,191 were built on Ipomoea carnea vegetation and 136 on open water. The birds used twigs of Ipomoea carnea and various parts of eight other plant species as nest material. The nests were elliptical in shape, with flattened upper surfaces containing nest cup and a ramp-like structure each. 49.96 % of nests were found within 50 m distance from the edge of wetlands. A total of 16 plant species were identified as food sources including five algal species, such as Aphanothece stagnina , Spirogyra irregularis , Chara flaccida , C . vulgaris , and C . zeylanica . The Common Coots maintained strict territory during the breeding season and no other water birds were observed in the vicinity of their nesting and foraging sites. Even after completion of the breeding season, sporadic nesting was observed by a few pairs till June 2022.


INTRODUCTION
The Eurasian Coot or Common Coot Fulica atra (Linnaeus, 1758) (Aves: Gruiformes: Rallidae) is a sexually monomorphic, monogamous, gregarious, aggressive, and territorial bird. The Common Coot occurs as an extant species (resident) in India, Sri Lanka, Nepal, Bangladesh, Pakistan, Afghanistan, Bhutan, China, France, Germany, Egypt, Saudi Arabia, and the United Kingdom (BirdLife International 2019). The Common Coot has four subspecies, namely Fulica atra atra of India, southeastern Asia, Philippines, Europe, and northern Africa to Japan; Fulica atra lugubris of Java, Bali, northeastern New Guinea; Fulica atra novaeguineae of Central New Guinea and, Fulica atra australis of Australia and New Zealand (Gill et al. 2020). The IUCN Red List of Threatened Species has classified the species as 'Least Concern' (BirdLife International 2019).
The reproductive biology of the Common Coot was studied in North-east Algeria (Samraoui & Samraoui 2007) and in Heilonjiang Province of China (Zhang et al. 2018). Common Coots have been reported breeding in Gujarat (Himmatsinhji et al. 1991;Patel et al. 1998), Maharashtra (Khacher 1978), Andhra Pradesh (Nadarajan et al. 1993), and Tamil Nadu (Balachandran 1994;Santharam 1996). No other literature is available on the nesting and foraging behaviours of the Common Coot in Tamil Nadu. In order, to fill the gap, the present study was carried out.
In this study, I documented the number of birds and nests, and the roosting and foraging habits of the Common Coot in the wetlands of Viluppuram District in Tamil Nadu. This study aimed to investigate the number of individuals of the Common Coot inhabiting the wetlands during the breeding season, the source of their nesting materials and food, and the total number of nests. Additionally, roosting and foraging behaviours and interactions with other bird species were addressed.

Study area
The present study was carried out at 30 sites in the wetland areas covering 29 villages in the Viluppuram District (12.0579 o N & 79.5603 o E), of Tamil Nadu (Table  1). Except for the Veedur reservoir other wetlands are seasonal and found dry during the summer months of June-August. These wetlands get filled in the Northeast monsoon during October-December every year. The vegetation at the study sites mainly consisted of herbs like Ipomoea carnea, reeds/grass Typha angustifolia, and Chrysopogon zizanoides, and trees such as Vachellia niliotica and Prosopis juliflora. Agriculture is the primary occupation in the district. The major crops of the area are Paddy Oryza sativa, Jowar Sorghum bicolor, Pearl Millet Pennisetum glaucum, Finger Millet Eleusine coracana, Foxtail Millet Setaria italica, Sugarcane Saccharum officinarum, and Pulses, such as Black gram Vigna mungo, Green gram Vigna radiata, and Pigeon pea Cajanus cajan. Temperature ranges 36-20 o C. The average annual rainfall is 1,060 mm (Viluppuram 2021).

Methods
With the help of two field assistants, the survey was conducted in the wetlands of Veedur Reservoir and wetlands of other areas in the district between 0545 and 1800 h, during the breeding season from the third week of December 2021 to the fourth week of March 2022. The number of birds was counted by following the total count method (Bibby et al. 2000) when the birds were foraging. Bird census was carried out over three monthly sessions during the second week of every month for three months and the bird population size was arrived at as the average of each session's total count. Chicks at various developmental stages were counted during March 2022. Variables such as nesting sites, sources of nest materials, and food sources, such as algae and angiosperm plants foraged by the birds were identified. The distance between the nests and the edges of water bodies was measured using measurement tape after the breeding season. The distance between the nests and edges of the water body was grouped into intervals 0-50, 51-100, 101-150, and 151-200 m. The exterior length and width of the nests as well as the length, width, depth of nest cups, and the height of nests above the water level were measured using a measuring tape after the nests (20) were abandoned by the birds. The count of adult, and juvenile birds, their roosting and foraging activities, and interactions with other water bird species within the wetland were observed using binoculars from a safe distance (ca. 30 m). All the guidelines and protocols of nesting studies, as prescribed by Barve et al. (2020) were followed scrupulously. No eggs, chicks, and adult birds were handled during the study. The locations of nesting sites were determined using Garmin Etrex 20x GPS device. Photographs and videos were taken using Nikon P1000 digital camera. The collected data were tabulated, analyzed and shown as a graphical representation.  (Table 1).

Nest construction
Nine plant species belonging to seven genera and seven families were utilized by the Common Coot as nesting materials. Of the nine plant species, eight were dicotyledons and one monocotyledon. The birds utilized various plant parts such as twigs, petioles, leaves, inflorescence, and even entire plants as nesting material. During nest construction, Common coots used live and dead twigs of I. carnea, formed base-like structures for nests and added dry twigs brought from nearby places. The nests are elliptical with a flattened upper surface containing the nest cup. The major part of the nest consisted of twigs of I. carnea. Open nests were built on leaves of Nymphaea spp. or Aponogeton natans using the twigs of I. carnea along with various parts of other plant species (Table 2). Moreover, they added leaves and inflorescence of grass C. zizanoides in the inner surface of the nest cup as egg lining. Even during incubation, many nests contained partly eaten fruits of species of genera Nelumbo and Nymphaea (Image 1,3b).
Abandoned nests (n = 20) after the breeding season revealed that the nests were found 12-18 cm height above the water level. The entire length of the nests including nest cups was in the range of 64.7±21.79 cm and the width was in the range of 46.95±17.56 cm. The length of the elliptical-shaped nest cup was in the range of 21.3±3.29 cm and the width of the nest cup was 9.85±2.52 cm. The depth of the nest cup was in the range of 7.45±2.63 cm.
Distance between the edges of water bodies and the locations of nests (both open nests and nests on vegetation) revealed that a maximum of 49.96 % of nests (n = 663) occurred within 50 m distance from the edges and 1.88% of nests (n = 25) between 151 and 200 m distance from edges of water bodies. The percentage of nests that occurred at various distance interval ranges is given in Figure 2. The clutch size ranged 3-8 eggs.
The study revealed that the adult birds continued to expand their nests even after the chicks had grown by adding plant materials and used the nests as roosting sites. It was observed that chicks also brought plant materials and added them to the nests. The size of the nest cup was relatively small when compared to the overall upper surface area of the nest. Apart from the nest cup, each nest contained a peculiar ramp-like structure on the margin. Whenever residents entered the water to harvest lotus/lilies or for fishing, young chicks jumped into the water, swam, temporarily hid in the nearby I. carnea vegetation and later returned to the nests by climbing through the ramps (Image 2j,k). Even partly grown-up chicks used the ramps to climb into their nests. The present study revealed that the breeding of the Common Coot concluded during the fourth week of March 2022. Sporadic nesting (11 nests in May and eight nests in June), however, was observed till the second week of June 2022.

Foraging
In the present study, 16 plant species belonging to nine families foraged by the Common Coot were observed. Out of the 16 species, five were algae (thallophytes), a solitary grass species C. dactylon (monocotyledon) and the remaining 10 species were dicotyledons. The Common Coots swallowed entire colonies of blue-green alga Aphanothece stagnina and thalli of macro green algae Spirogyra irregularis and Chara spp. The birds usually dive into the water and cut off fruits of Nelumbo nucifera and Nymphaea spp. along with peduncles submerged in water, take them and placed them in the nests, pluck seeds using beaks, and feed their chicks. Adults were also observed consuming such seeds. Apart from hydrophytes, adult birds were found foraging on terrestrial plants, such as C. dactylon and Phyla nodiflora on the banks of water bodies. A list of plant species and their parts consumed by the birds is given in Table 3. In three instances, the adults collected small insects on the leaves of Nymphaea spp. and placed them in front of young chicks in the nests and the chicks swallowed the prey. Eight abandoned nests contained empty shells of snails.

Chicks
A total of 467 chicks at various developmental stages were enumerated at the end of the breeding period. Eighty-nine adults were found moving with a single chick each, 81 adults had two chicks each, 41 adults had three chicks each, eight adults had four chicks each, and the remaining 61 chicks were found wandering independently without any adult/parent birds probably because the parents had abandoned them or the parent birds might have been killed by predators (Image 2f,g).

Interactions with other birds and threats
Common Coots maintained strict nesting territory during the breeding season and no other water birds were observed in the vicinity of their nesting and foraging sites. Other water bird species, such as Little Egret Egretta garzetta, Lesser Duck Aythya affinis, Indian Spotbilled Duck Anas poecilorhyncha, Pheasant-tailed jacana Hydrophasianus chirurgus, Little Grebe Tachybaptus ruficollis and Lesser Whistling Duck Dendrocygna javanica were found foraging in the water bodies where nests of the Common Coot occurred. Individual Common Coots used to chase/attack when other bird species come in the vicinity of their nesting and foraging sites. Other bird species stop their activities like swimming, foraging, preening, or perching on aquatic plants, and become alert and ready to escape whenever a Common Coot moves nearby. In four instances, individuals of Pheasanttailed Jacana used abandoned nests of Common Coot as a day roost. Fishing by locals caused disturbance to the foraging of adults and chicks. No killing of adult birds/ nest predation, however, was observed (Image 4).

Nest construction
In southern Algeria, 63.2% of nests of Common Coot were associated with Phragmites australis probably to reduce predation risk from the air (Samraoui & Samraoui 2007). Emergent vegetation is important for habitat selection by Coots, presumably because it provides nesting habitats and protection against aerial predators (Nieoczym & Kloskowski 2018). In the present study, 89.75% of nests were built in emergent vegetation I. carnea probably to avoid aerial predators as stated by Samraoui & Samraoui (2007) and Nieoczym & Kloskowski (2018). Most of the nests of Common Coot were associated with T. angustifolia in Algerian Sahara (El-Yamine et al. 2018). Though T. angustifolia reeds occurred abundantly in the present study area, the birds did not build nests on these reeds, whereas they preferred I. carnea vegetation. The study also revealed that 50% of the nests occurred within 0-50 m and another 35.19% of nests occurred within 51-100 m Studies over larger geographical areas, however, may throw light on the causes for the construction of more nests near the edges of water bodies. Common Coots rarely raise two broods per season (Taylor 1998). The present study reveals that despite the conclusion of breeding during the fourth week of March 2022, sporadic nesting by a few pairs continued till the second week of June 2022. It was not possible to ascertain whether these were cases of late breeding or it was a second breeding in the year. Nests often remain used by the family for roosting (Taylor 1998). In the study sites, adult Common Coots with their juveniles not only used their nests for roosting but also expanded the existing nests further by adding fresh nest materials. These observations corroborate the findings of Taylor (1998).

Foraging
The Common Coot is omnivorous, feeding on small prey, eggs of other birds, algae, vegetation, seeds and fruits (Martin et al. 1997). Sago pondweed Stuckenia pectinata in France and Germany (Allouche & Tamisier 1984;Hilt 2006) and Watermilfoil Myriophyllum verticillatum and horn-wort Ceratophyllum demersum in China are their main sources of food (Wang et al. 1990;Zhang & Ma 2011). Submerged vegetation is an important food source for Common Coot and it is positively related to its breeding success (Nieoczym & Kloskowski 2018). The Common Coots exhibit considerable plasticity in their foraging behaviours by foraging on a wide range of plants and animal materials,   www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.