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Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India
Journal of Asia-Pacific Biodiversity xxx (2018) 1e6
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Original Article
Population status, habitat preference, and nesting characteristics of blackheaded ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India Sunil Chaudhury, Vijay Kumar Koli* Wildlife Research Laboratory, Department of Zoology, University College of Science, Mohanlal Sukhadia University, Udaipur, Rajasthan, 313001, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 7 November 2017 Received in revised form 9 January 2018 Accepted 29 January 2018 Available online xxx
The black-headed ibis Threskiornis melanocephalus is a medium sized (65e75 cm long) wading, nomadic Ciconiiform waterbird, gregariously frequenting shallow habitats. It is wide-ranging species distributed across the Asian continent and categorized as “Near Threatened” by IUCN (International Union for Conservation of Nature) because of decreasing population status from the last few decades. The present work describes the current population status, habitat preference in response to seasonal variation, and nesting characteristics of black-headed ibis T. melanocephalus in southern Rajasthan, India. Different surveys were performed in the study area at different temporal and spatial scales to assess different aspects. A total of 580 individuals (496 adults and 84 juveniles) were recorded during 2016, while 643 individuals (547 adults and 96 juvenile) in 2017. Juveniles represented 14.7% of the total population. The overall adultejuvenile ratio was 0.16 in 2016 and 0.17 in 2017. The encountered birds were found not significantly different seasonally in distinct microhabitats in both years (p < 0.05); highest number was recorded in seasonal wetlands. Nesting sites were recorded in two districts (i.e. Udaipur and Dungarpur) along with eight other waterbird species. Cattle egrets Bubulcus ibis was the most commonly associated nesting species, while babul Acacia nilotica and vilayati babul Prosopis juliflora were the most preferred nesting tree species. Ó 2018 National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA), Publishing Services by Elsevier. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: black-headed ibis Habitat preference India Nesting ecology Population status
Introduction The black-headed ibis Threskiornis melanocephalus is a medium sized (65e75 cm long) wading, nomadic Ciconiiform waterbird, gregariously frequenting shallow habitats (Hancock et al 2001; Ali and Ripley 2007). It is distributed across India, Pakistan, Sri Lanka, Nepal, China, Bangladesh, Myanmar, Thailand, Vietnam, Cambodia, and rare visitor to Japan, Indonesia, and Philippines (Hancock et al 2001; Ali and Ripley 2007; BirdLife International 2012). It roosts and nests in colonies called “heronries or egretries”, situated in and around wetlands, often associated with the Ciconiiform and Pelecaniform waterbirds (Balakrishnan and Thomas 2004). In mixed species colonies, black-headed ibis T. melanocephalus tends to form a discrete core group and avoids interspersed nesting pattern with other aquatic bird species. The nest of black-headed ibis
* Corresponding author. Tel.: þ919252239657. E-mail address: [email protected] (V.K. Koli). Peer review under responsibility of National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA).
T. melanocephalus is a platform of twigs and sticks, lined with grass and threads, constructed on the top of trees and shrubs, like Acacia, Prosopis, and various species of Ficus (Senma and Acharya 2010). It usually collects nesting materials from trees, but the use of threads and pieces of plastic bags are also reported (Senma and Acharya 2010). Only few nesting colonies of black-headed ibis T. melanocephalus are known from India. In the western part, nesting was reported only from Gujarat state (Tiwari and Rahmani 1998; Gadhvi and Soni 2006; Senma and Acharya 2010) while from Kerala in South India (Balakrishnan and Thomas 2004; Narayanan et al 2006). Similarly, successful breeding is also reported in captivity (Devkar et al 2006). This species is categorized in “Schedule IV” under the Indian Wildlife Protection Act (1972), while as “Near Threatened” by IUCN (International Union for Conservation of Nature) because of decreasing population status from the last few decades (BirdLife International 2012). Hunting, trade, agricultural pollution, and habitat destruction and degradation are identified as its main threats in the wild (BirdLife International 2012; Koli et al 2013a). Population estimation of a bird species helps to assess its current status, understand the extent of threats, an interaction
https://doi.org/10.1016/j.japb.2018.01.013 pISSN2287-884X eISSN2287-9544/Ó 2018 National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA), Publishing Services by Elsevier. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article in press as: Chaudhury S, Koli VK, Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India, Journal of Asia-Pacific Biodiversity (2018), https://doi.org/10.1016/ j.japb.2018.01.013
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between species, and energy flow among trophic levels. Early identification of declining population can focus research and management effort of threatening species and its habitat before it becomes extinct (Thomas and Martin 1996; Holmes and Sherry 2001). Reporting of only few breeding sites of black-headed ibis T. melanocephalus in India along with its decreasing population status urges more species-specific research on this important aquatic bird species. Therefore, in this study, our objectives were to estimate (1) the current population status, (2) habitat preference in response to seasonal variation, and (3) nesting characteristics of black-headed ibis T. melanocephalus.
Material and methods Study area The southern part of Rajasthan state is commonly known as the “Mewar” region, includes six districts, namely, Udaipur, Rajsamand, Dungarpur, Banswara, Pratapgarh, and Chittorgarh (Figure 1), covering about 12.35% geographical area of the state (Koli et al 2013b). This part is located in the world’s oldest Aravalli Mountain Range, having many seasonal and perennial water bodies, supporting sound waterbirds’ diversity. The average rainfall of this region is about 602 mm with a distinct winter (Novembere February), summer (MarcheJune), and monsoon (JulyeOctober)
seasons. The highest temperature (c. 42 C) was recorded in summer and lowest (c. 8 C) in the winter season. The landscape is mosaic with natural and seasonal wetlands, agriculture fields, mountain ranges, and human habitations. Methodology Different surveys at different temporal and spatial scales were performed in the study area for data collection, from 1 January 2016 to 31 September 2017. To assess the population status, a road transect survey of 2558 km (including 356 km in Rajsamand, 563 km in Udaipur, 320 km in Dungarpur, 711 km in Banswara, 293 km in Pratapgarh, and 318 km in Chittorgarh) was carried out during the summer season in the month of June of 2016 and 2017, since wetlands shrink in this season, possibly forcing individuals of the waterbirds’ flock to the left over wetlands (Sundar 2006; Koli et al 2013a). Road surveys were decided to cover maximum wetlands of the districts. Two or three days were taken to complete the transect route in each district to minimize the effects of birds’ local migration and also prevent the possibility of a double count. At each wetland, birds were counted from a vantage point using binoculars, but if a reservoir was too big to be scanned from one place, the whole periphery was circumambulated by walking together to count. Walking distance around the periphery of the wetlands was not included in the transect length.
Figure 1. Scanned during the road transect survey for population status assessment of black-headed ibis Threskiornis melanocephalus in southern Rajasthan: A, locations of the study area; B, locations of the study wetlands.
Please cite this article in press as: Chaudhury S, Koli VK, Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India, Journal of Asia-Pacific Biodiversity (2018), https://doi.org/10.1016/ j.japb.2018.01.013
S Chaudhury, VK Koli / Journal of Asia-Pacific Biodiversity xxx (2018) 1e6 Table 1. Habitats’ description of black-headed ibis Threskiornis melanocephalus in southern Rajasthan, India. S. no.
Habitat
Description
1 2 3
Agriculture crop field Irrigation canal Grazing area
4
Seasonal wetland
5 6 7 8
Perennial wetland Sewage line Municipal garbage Others
Fields using for crop plantation Network of canal used for crop irrigation Waste land with low height scrubs and grasses supporting cattle grazing Water body retain water only in a particular time period of the year Water body retain water throughout the year Open sewage lines in city area Dumping sites of garbage Include human habitation, roadsides, scrubland etc.
To assess the habitat preference, daytime seasonal surveys (without rain and fog) were conducted on a predetermined route crossing many habitats (i.e. agriculture crop field, irrigation canal, grazing area, seasonal and perennial wetlands, sewage line, municipal garbage, and others; Table 1) in and around Udaipur district within the first week of selected month in each season; January for winter, June for summer and September for monsoon. The survey was started within 1 hour of sunrise till 10.30 h as per description by Sundar (2006), and the number of individuals along with habitat was noted. During the surveys, nesting sites of black-headed ibis T. melanocephalus were also noted whenever observed. Nesting site
3
was confirmed when the active nest was observed at the site and following parameters were noted to describe site characteristics: nesting tree species, available tree species around the nesting tree (within 100 m radius), uppermost nest height (m), lowermost nest height (m), girth at breast height of nesting tree (m), location of nests in tree canopy (in mid canopy, upper canopy, or lower canopy), distance to human habitation (m), distance to water (m), communal nesting species in colony, and number of the nests of communal nesting species and black-headed ibis T. melanocephalus in colony. Tree heights and nest heights were measured using clinometer. Statistical analysis Dice’s “association index” (Rabenold 1986) was used to assess the nesting association of black-headed ibis T. melanocephalus with other species. The formula is as follows:
Dice’s association index ¼
2c ð2c þ a þ bÞ
where, c is the number of colonies where both species A (i.e. blackheaded ibis T. melanocephalus) and B (other communal species) occurs, a is the number of colonies where only species A is present, while b is the number of colonies where only species B occurs. The index value varies between 1 (complete association) and 0 (complete avoidance).
Figure 2. A, Encounter rates of black-headed ibis, Threskiornis melanocephalus in all districts; B, district wise number of adults and juveniles recorded during the road transect survey in southern Rajasthan, India. Number on each bar is indicating adultejuvenile ratio.
Please cite this article in press as: Chaudhury S, Koli VK, Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India, Journal of Asia-Pacific Biodiversity (2018), https://doi.org/10.1016/ j.japb.2018.01.013
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Encounter rate was calculated as the number of birds counted on transect (abundance)/total length of the transect (km), while adult and juvenile ratio was calculated by dividing the number of juvenile by the number of adults. The normality of data was tested with ShapiroeWilk test. For multiple-group comparison of nonnormally distributed data, we used KruskaleWallis analysis of variance to test the hypothesis that there is no seasonal difference that occurs among the encounter number of birds in different microhabitats, while the Pearson product moment correlation (r) was used to test the null hypothesis that the counted number of birds during the survey is not related to the length of transects laid in districts. The results were considered significant at p < 0.05 level. All statistical analysis was performed by GraphPad Prism statistical software (ver. 3.02) (Motulsky 1999). Results A total of 580 individuals (496 adults and 84 juveniles) were recorded during 2016, while 643 individuals (547 adults and 96 juvenile) in 2017. Juvenile represented 14.7% of the total population. The highest number (n ¼ 181) of individuals was recorded in Udaipur district, while lowest (n ¼ 45) in Pratapgarh district during 2016; similarly in 2017, the highest number was in Banswara (n ¼ 170) and lowest in Rajsamand (n ¼ 74) (Figure 2). The overall encountered rate was 0.86, vary in districts (Figure 2). The recorded number of birds was insignificantly correlated with length of transects laid in the districts in 2016 (r ¼ 0.42, n ¼ 6, p ¼ 0.39) but significant in 2017 (r ¼ 0.89, n ¼ 6, p ¼ 0.01). The overall adultejuvenile ratio was 0.16 in 2016 and 0.17 in 2017. The encountered numbers of black-headed ibis T. melanocephalus were not significantly different seasonally in distinct microhabitats in 2016 (KruskaleWallis: H ¼ 1.06, df ¼ 7, p < 0.05) and also in 2017 (KruskaleWallis: H ¼ 1.06, df ¼ 7, p < 0.05). The highest number was recorded in seasonal wetlands followed by sewage line, perennial wetland, grazing open area, irrigation canal, crop field, municipal garbage sites, and others (Figure 3), respectively. Seasonal wetlands were the most preferred site during winter and summer seasons, while during the rainy season, the highest number was recorded in grazing and sewage lines. Nesting colonies of black-headed ibis T. melanocephalus were recorded in Udaipur and Dungarpur (Table 2), with eight other waterbird species (Table 3). Cattle egrets Bubulcus ibis was the most commonly associated species in all nesting sites, followed by great egrets Casmerodius, little cormorant Phalacrocorax niger, little egrets Egretta garzetta, Eurasian spoonbill Platalea leucorodia, Asian openbill Anastomus oscitans, painted stork Mycteria leucocephala, and night heron Nycticorax nycticorax, respectively (Tables 3 and 4). The highest number of other communal species (n ¼ 8) along with black-headed ibis T. melanocephalus was recorded in Dhambola wetland (Table 2). Similarly, the highest number (n ¼ 50) of blackheaded ibis T. melanocephalus nests were also recorded in the same wetland (Table 3). The preferred nesting tree was babul Acacia nilotica (at seven sites), followed by vilayati babul Prosopis juliflora (at two sites), tamarind Tamarindus indica and Manila tamarind Pithecellobium dulce (at a single site), respectively. Other parameters are shown in Table 2. Discussion During the study, a total of 580 individuals of black-headed ibis T. melanocephalus were recorded in 2016, while 643 in 2017, which was more than the survey performed by Koli et al (2013a) in the same area during 2008 and 2009. In our study, the highest number of black-headed ibis T. melanocephalus was recorded in Udaipur district and lowest was in Pratapgarh during 2016, whereas in 2017,
Figure 3. Percentage of individuals sighted in different microhabitats during the survey: A, 2016; B, 2017. CF ¼ agriculture crop field; GA ¼ grazing area; IC ¼ irrigation canal; MG ¼ municipal garbage; O ¼ others; PW ¼ perennial wetland; SL ¼ sewage line; SW ¼ seasonal wetland.
the highest number was noted in Banswara and lowest in Rajsamand. On contrary, Koli et al (2013a) found the highest number of individuals for both years in Chittorgarh, while lowest in Udaipur during 2008 and in Pratapgarh during 2009. This variation in the number in both studies might be because of the difference in sampling efforts; we scanned 69 wetlands, while Koli et al (2013a) surveyed only 28 wetlands. Besides this, the difference in the number of our surveys conducted both years strongly supports frequent local migration of the species, which can be derived by irregular rainfall pattern in the study area. Microhabitat preference of black-headed ibis T. melanocephalus changed seasonally in our study. Seasonal wetlands were the most preferred habitat, likely due to that they provide optimal feeding ground in the form of the large marshy open area than perennial wetlands. Use of sewage line throughout all seasons may be because of high chironomid larvae and oligochaetes density, which is often close to vegetation or in moist soil in standing water (Frederick and Bildstein 1992; Safran et al 2000; Sundar 2006). Seasonal water level variations in different habitats may cause variations in abundance, foraging, and diet of large waterbirds owing to changes in the availability of resources (Kushlan 1981; González 1997; Sundar 2006). Therefore, few encounters in monsoon season were may be due to high water availability throughout the area (Figure 3), which increases population dispersion. Grazing area, sewage lines, and crop fields were providing supporting habitats in monsoon when marshy open
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Table 2. Nesting sites, nesting tree species, and nest site characteristics of black-headed ibis Threskiornis melanocephalus in southern Rajasthan, India. District
Nesting site
Site code
Tree species
Available trees
TH (m)
UNH (m)
LNH (m)
GBH (m)
Preferred tree canopy
DTH (m)
DTW (m)
DTR (m)
Udaipur
Dhamawadi Ekling talab Roopsagar Udaisagar Lake Sintex tiraha, (D1) Ladsar village, (D2) Padli gujreshwer, village site 1 Padli gujreshwer, Village Site 2 Padli gujreshwer, village site 3 Padli gujreshwer, village site 4 Karawara village site 1 Karawara village site 2 Dhambola Talab
U1 U2 U3 U4 D1 D2 D3 D4 D5 D6 D7 D8 D9
Acacia nilotica Acacia nilotica Prosopis juliflora Acacia nilotica Pithecellobium dulce Acacia nilotica Acacia nilotica Acacia nilotica Acacia nilotica Prosopis juliflora Acacia nilotica Tamarindus indica Acacia nilotica
AN, PJ, EG, AI, ZM AN, AI, FR PJ, AN, AI, FR AN, PS, AN, PJ, EG, AI EG, AI, MI EG, AI, MI EG, AI, MI EG, AI, MI AN, AI -
8.7 8 5 9 10.5 13.3 15 7 15 11 8 13 14
7 7.5 4.7 6.3 9 12.5 13.2 6.8 14 9.5 6.4 12.3 13
6.4 7 4.5 5 8.5 11 11.8 6 12 9 6 12 1
0.50 0.30 0.15 0.30 0.50 0.5 1 0.4 0.80 1 0.3 1 0.5
Mid canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Mid canopy Mid canopy Upper canopy Upper canopy
28 100 50 30 5 100 5 8 13 12 10 2 200
8 2 3 2 1500 0 50 40 5 20 0 1 0
3 90 60 70 0.5 70 0.5 1 1.5 4 7 10 500
Dungerpur
AN ¼ Acacia nilotica; AI ¼ Azadirachta indica; EG ¼ Eucalyptus globulus, MI ¼ Mangifera indica; PJ ¼ Prosopis juliflora; ZM ¼ Ziziphus mauritiana. Nest site characters: TH ¼ tree height; UNH ¼ uppermost nest height; LNH ¼ lowermost nest height; GBH ¼ girth at breast height; DTH ¼ distance to human habitation; DTW ¼ distance to water; DTR ¼ distance to road. “-” indicate no available tree.
Table 3. The number nests of black-headed ibis Threskiornis melanocephalus and communal species, recorded in different nesting colonies of southern Rajasthan, India. For site name, refer code with Table 2. Species
Scientific name
U1
U2
U3
U4
D1
D2
D3
D4
D5
D6
D7
D8
D9
Cattle egrets Great egrets Little egrets Eurasian spoonbill Asian openbill Little Cormorant Painted stork Night heron Black-headed ibis Total
Bubulcus ibis Casmerodius albus Egretta garzetta Platalea leucorodia Anastomus oscitans Phalacrocorax niger Mycteria leucocephala Nycticorax nycticorax Threskiornis melanocephalus
20 5 0 0 0 0 0 0 13 38
10 0 0 0 0 7 0 0 8 25
22 3 7 0 15 16 0 0 35 98
5 0 0 0 0 3 0 0 12 20
15 5 6 0 0 3 0 0 8 37
8 3 0 0 5 8 0 0 13 37
4 2 3 0 8 0 0 0 3 20
20 8 9 0 13 11 0 0 10 71
35 10 12 3 0 7 0 3 15 85
15 4 0 0 0 2 0 0 9 30
20 7 8 0 0 4 0 0 4 43
40 15 13 0 0 8 0 0 27 103
50 17 12 8 15 35 25 15 50 227
Table 4. Association of black-headed ibis (BHI) with other species at nesting sites. Pair (aeb)
BHI-CE BHI-GE BHI-LC BHI-LE BHI-AO BHI-ES BHI-NH BHI-PS
Number of censuses including A and B (c)
A only (a)
B only (b)
13 11 11 8 5 2 2 1
0 2 2 5 8 11 11 11
0 0 0 0 0 0 0 0
Dice’s association index 1.00 0.92 0.92 0.76 0.50 0.35 0.26 0.13
AO ¼ Asian openbill; CE ¼ cattle egret; ES ¼ European spoonbill; GE ¼ great egret; LC ¼ little cormorant; LE ¼ little egrets; NH ¼ night heron; PS ¼ painted stork.
areas around wetlands become submerged. This season is also considered the breeding season of black-headed ibis T. melanocephalus in India (Tiwari and Rahmani 1998; Gadhvi and Soni 2006), which aggregate individuals in breeding colonies and ultimately decreases birds’ encounter in open areas. In summer and winter, shallow seasonal wetlands attracted ibises possibly due to suitable shallow feeding areas in few seasonal wetlands than the monsoon. Municipal garbage along with rotten vegetable matter and carcass also provided additional feeding sites to black-headed ibis T. melanocephalus in the study area (Chaudhury and Koli 2016). Use of grazing area and crop field increased in monsoon. Grazing areas were used for resting, but in crop fields, black-headed ibis T. melanocephalus, observed along with cattle egrets during sowing, might be in search of insects as food items (per observ.). During our study, nesting of black-headed ibis T. melanocephalus was found in human habitation, near wetlands and in the islands, while most preferred nesting trees were A. nilotica and P. juliflora.
Most nests were found in the middle and upper canopy areas of trees. It seems that the species choose nesting site after careful assessment of the safety conditions along with the nearby foraging area. Since nesting colonies in unmanned areas are severely attacked by natural predators and late nesters are more prone to predatory loss of nestlings, the waterbirds usually tend to form breeding colonies near human habitations. Thorny nesting trees restrict access to ground predators such as snakes and also protect nest against storm and downpour. Patanakar (2004) reported regular black-headed ibis T. melanocephalus nesting in suburban areas, indicating its adaptability in nesting site selection. Thick canopy prevents the chick falling directly on the ground and reduces thermal stress to young ones (Dayananda and Hosetti 2009; Senma and Acharya 2010), and nesting on upper canopy height could be advantageous in alighting from a flight. In sum, southern Rajasthan is supporting a sound population of black-headed ibis T. melanocephalus. The highest number of population recorded is from Udaipur while lowest was recorded in Pratapgarh district. The species also showed seasonal variation in habitat preference. Nesting sites were recorded from two districts, and A. nilotica and P. juliflora were the most preferred nesting tree species. Conflicts of interest The authors declare that there is no conflicts of interest. Acknowledgments The authors thank Virendra Singh Bedsa, Kamlesh Ii, and Dr Anil Tripathi for assistance in fieldwork. The work is not funded by any agency.
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Original Article
Population status, habitat preference, and nesting characteristics of blackheaded ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India Sunil Chaudhury, Vijay Kumar Koli* Wildlife Research Laboratory, Department of Zoology, University College of Science, Mohanlal Sukhadia University, Udaipur, Rajasthan, 313001, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 7 November 2017 Received in revised form 9 January 2018 Accepted 29 January 2018 Available online xxx
The black-headed ibis Threskiornis melanocephalus is a medium sized (65e75 cm long) wading, nomadic Ciconiiform waterbird, gregariously frequenting shallow habitats. It is wide-ranging species distributed across the Asian continent and categorized as “Near Threatened” by IUCN (International Union for Conservation of Nature) because of decreasing population status from the last few decades. The present work describes the current population status, habitat preference in response to seasonal variation, and nesting characteristics of black-headed ibis T. melanocephalus in southern Rajasthan, India. Different surveys were performed in the study area at different temporal and spatial scales to assess different aspects. A total of 580 individuals (496 adults and 84 juveniles) were recorded during 2016, while 643 individuals (547 adults and 96 juvenile) in 2017. Juveniles represented 14.7% of the total population. The overall adultejuvenile ratio was 0.16 in 2016 and 0.17 in 2017. The encountered birds were found not significantly different seasonally in distinct microhabitats in both years (p < 0.05); highest number was recorded in seasonal wetlands. Nesting sites were recorded in two districts (i.e. Udaipur and Dungarpur) along with eight other waterbird species. Cattle egrets Bubulcus ibis was the most commonly associated nesting species, while babul Acacia nilotica and vilayati babul Prosopis juliflora were the most preferred nesting tree species. Ó 2018 National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA), Publishing Services by Elsevier. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: black-headed ibis Habitat preference India Nesting ecology Population status
Introduction The black-headed ibis Threskiornis melanocephalus is a medium sized (65e75 cm long) wading, nomadic Ciconiiform waterbird, gregariously frequenting shallow habitats (Hancock et al 2001; Ali and Ripley 2007). It is distributed across India, Pakistan, Sri Lanka, Nepal, China, Bangladesh, Myanmar, Thailand, Vietnam, Cambodia, and rare visitor to Japan, Indonesia, and Philippines (Hancock et al 2001; Ali and Ripley 2007; BirdLife International 2012). It roosts and nests in colonies called “heronries or egretries”, situated in and around wetlands, often associated with the Ciconiiform and Pelecaniform waterbirds (Balakrishnan and Thomas 2004). In mixed species colonies, black-headed ibis T. melanocephalus tends to form a discrete core group and avoids interspersed nesting pattern with other aquatic bird species. The nest of black-headed ibis
* Corresponding author. Tel.: þ919252239657. E-mail address: [email protected] (V.K. Koli). Peer review under responsibility of National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA).
T. melanocephalus is a platform of twigs and sticks, lined with grass and threads, constructed on the top of trees and shrubs, like Acacia, Prosopis, and various species of Ficus (Senma and Acharya 2010). It usually collects nesting materials from trees, but the use of threads and pieces of plastic bags are also reported (Senma and Acharya 2010). Only few nesting colonies of black-headed ibis T. melanocephalus are known from India. In the western part, nesting was reported only from Gujarat state (Tiwari and Rahmani 1998; Gadhvi and Soni 2006; Senma and Acharya 2010) while from Kerala in South India (Balakrishnan and Thomas 2004; Narayanan et al 2006). Similarly, successful breeding is also reported in captivity (Devkar et al 2006). This species is categorized in “Schedule IV” under the Indian Wildlife Protection Act (1972), while as “Near Threatened” by IUCN (International Union for Conservation of Nature) because of decreasing population status from the last few decades (BirdLife International 2012). Hunting, trade, agricultural pollution, and habitat destruction and degradation are identified as its main threats in the wild (BirdLife International 2012; Koli et al 2013a). Population estimation of a bird species helps to assess its current status, understand the extent of threats, an interaction
https://doi.org/10.1016/j.japb.2018.01.013 pISSN2287-884X eISSN2287-9544/Ó 2018 National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA), Publishing Services by Elsevier. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article in press as: Chaudhury S, Koli VK, Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India, Journal of Asia-Pacific Biodiversity (2018), https://doi.org/10.1016/ j.japb.2018.01.013
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between species, and energy flow among trophic levels. Early identification of declining population can focus research and management effort of threatening species and its habitat before it becomes extinct (Thomas and Martin 1996; Holmes and Sherry 2001). Reporting of only few breeding sites of black-headed ibis T. melanocephalus in India along with its decreasing population status urges more species-specific research on this important aquatic bird species. Therefore, in this study, our objectives were to estimate (1) the current population status, (2) habitat preference in response to seasonal variation, and (3) nesting characteristics of black-headed ibis T. melanocephalus.
Material and methods Study area The southern part of Rajasthan state is commonly known as the “Mewar” region, includes six districts, namely, Udaipur, Rajsamand, Dungarpur, Banswara, Pratapgarh, and Chittorgarh (Figure 1), covering about 12.35% geographical area of the state (Koli et al 2013b). This part is located in the world’s oldest Aravalli Mountain Range, having many seasonal and perennial water bodies, supporting sound waterbirds’ diversity. The average rainfall of this region is about 602 mm with a distinct winter (Novembere February), summer (MarcheJune), and monsoon (JulyeOctober)
seasons. The highest temperature (c. 42 C) was recorded in summer and lowest (c. 8 C) in the winter season. The landscape is mosaic with natural and seasonal wetlands, agriculture fields, mountain ranges, and human habitations. Methodology Different surveys at different temporal and spatial scales were performed in the study area for data collection, from 1 January 2016 to 31 September 2017. To assess the population status, a road transect survey of 2558 km (including 356 km in Rajsamand, 563 km in Udaipur, 320 km in Dungarpur, 711 km in Banswara, 293 km in Pratapgarh, and 318 km in Chittorgarh) was carried out during the summer season in the month of June of 2016 and 2017, since wetlands shrink in this season, possibly forcing individuals of the waterbirds’ flock to the left over wetlands (Sundar 2006; Koli et al 2013a). Road surveys were decided to cover maximum wetlands of the districts. Two or three days were taken to complete the transect route in each district to minimize the effects of birds’ local migration and also prevent the possibility of a double count. At each wetland, birds were counted from a vantage point using binoculars, but if a reservoir was too big to be scanned from one place, the whole periphery was circumambulated by walking together to count. Walking distance around the periphery of the wetlands was not included in the transect length.
Figure 1. Scanned during the road transect survey for population status assessment of black-headed ibis Threskiornis melanocephalus in southern Rajasthan: A, locations of the study area; B, locations of the study wetlands.
Please cite this article in press as: Chaudhury S, Koli VK, Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India, Journal of Asia-Pacific Biodiversity (2018), https://doi.org/10.1016/ j.japb.2018.01.013
S Chaudhury, VK Koli / Journal of Asia-Pacific Biodiversity xxx (2018) 1e6 Table 1. Habitats’ description of black-headed ibis Threskiornis melanocephalus in southern Rajasthan, India. S. no.
Habitat
Description
1 2 3
Agriculture crop field Irrigation canal Grazing area
4
Seasonal wetland
5 6 7 8
Perennial wetland Sewage line Municipal garbage Others
Fields using for crop plantation Network of canal used for crop irrigation Waste land with low height scrubs and grasses supporting cattle grazing Water body retain water only in a particular time period of the year Water body retain water throughout the year Open sewage lines in city area Dumping sites of garbage Include human habitation, roadsides, scrubland etc.
To assess the habitat preference, daytime seasonal surveys (without rain and fog) were conducted on a predetermined route crossing many habitats (i.e. agriculture crop field, irrigation canal, grazing area, seasonal and perennial wetlands, sewage line, municipal garbage, and others; Table 1) in and around Udaipur district within the first week of selected month in each season; January for winter, June for summer and September for monsoon. The survey was started within 1 hour of sunrise till 10.30 h as per description by Sundar (2006), and the number of individuals along with habitat was noted. During the surveys, nesting sites of black-headed ibis T. melanocephalus were also noted whenever observed. Nesting site
3
was confirmed when the active nest was observed at the site and following parameters were noted to describe site characteristics: nesting tree species, available tree species around the nesting tree (within 100 m radius), uppermost nest height (m), lowermost nest height (m), girth at breast height of nesting tree (m), location of nests in tree canopy (in mid canopy, upper canopy, or lower canopy), distance to human habitation (m), distance to water (m), communal nesting species in colony, and number of the nests of communal nesting species and black-headed ibis T. melanocephalus in colony. Tree heights and nest heights were measured using clinometer. Statistical analysis Dice’s “association index” (Rabenold 1986) was used to assess the nesting association of black-headed ibis T. melanocephalus with other species. The formula is as follows:
Dice’s association index ¼
2c ð2c þ a þ bÞ
where, c is the number of colonies where both species A (i.e. blackheaded ibis T. melanocephalus) and B (other communal species) occurs, a is the number of colonies where only species A is present, while b is the number of colonies where only species B occurs. The index value varies between 1 (complete association) and 0 (complete avoidance).
Figure 2. A, Encounter rates of black-headed ibis, Threskiornis melanocephalus in all districts; B, district wise number of adults and juveniles recorded during the road transect survey in southern Rajasthan, India. Number on each bar is indicating adultejuvenile ratio.
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Encounter rate was calculated as the number of birds counted on transect (abundance)/total length of the transect (km), while adult and juvenile ratio was calculated by dividing the number of juvenile by the number of adults. The normality of data was tested with ShapiroeWilk test. For multiple-group comparison of nonnormally distributed data, we used KruskaleWallis analysis of variance to test the hypothesis that there is no seasonal difference that occurs among the encounter number of birds in different microhabitats, while the Pearson product moment correlation (r) was used to test the null hypothesis that the counted number of birds during the survey is not related to the length of transects laid in districts. The results were considered significant at p < 0.05 level. All statistical analysis was performed by GraphPad Prism statistical software (ver. 3.02) (Motulsky 1999). Results A total of 580 individuals (496 adults and 84 juveniles) were recorded during 2016, while 643 individuals (547 adults and 96 juvenile) in 2017. Juvenile represented 14.7% of the total population. The highest number (n ¼ 181) of individuals was recorded in Udaipur district, while lowest (n ¼ 45) in Pratapgarh district during 2016; similarly in 2017, the highest number was in Banswara (n ¼ 170) and lowest in Rajsamand (n ¼ 74) (Figure 2). The overall encountered rate was 0.86, vary in districts (Figure 2). The recorded number of birds was insignificantly correlated with length of transects laid in the districts in 2016 (r ¼ 0.42, n ¼ 6, p ¼ 0.39) but significant in 2017 (r ¼ 0.89, n ¼ 6, p ¼ 0.01). The overall adultejuvenile ratio was 0.16 in 2016 and 0.17 in 2017. The encountered numbers of black-headed ibis T. melanocephalus were not significantly different seasonally in distinct microhabitats in 2016 (KruskaleWallis: H ¼ 1.06, df ¼ 7, p < 0.05) and also in 2017 (KruskaleWallis: H ¼ 1.06, df ¼ 7, p < 0.05). The highest number was recorded in seasonal wetlands followed by sewage line, perennial wetland, grazing open area, irrigation canal, crop field, municipal garbage sites, and others (Figure 3), respectively. Seasonal wetlands were the most preferred site during winter and summer seasons, while during the rainy season, the highest number was recorded in grazing and sewage lines. Nesting colonies of black-headed ibis T. melanocephalus were recorded in Udaipur and Dungarpur (Table 2), with eight other waterbird species (Table 3). Cattle egrets Bubulcus ibis was the most commonly associated species in all nesting sites, followed by great egrets Casmerodius, little cormorant Phalacrocorax niger, little egrets Egretta garzetta, Eurasian spoonbill Platalea leucorodia, Asian openbill Anastomus oscitans, painted stork Mycteria leucocephala, and night heron Nycticorax nycticorax, respectively (Tables 3 and 4). The highest number of other communal species (n ¼ 8) along with black-headed ibis T. melanocephalus was recorded in Dhambola wetland (Table 2). Similarly, the highest number (n ¼ 50) of blackheaded ibis T. melanocephalus nests were also recorded in the same wetland (Table 3). The preferred nesting tree was babul Acacia nilotica (at seven sites), followed by vilayati babul Prosopis juliflora (at two sites), tamarind Tamarindus indica and Manila tamarind Pithecellobium dulce (at a single site), respectively. Other parameters are shown in Table 2. Discussion During the study, a total of 580 individuals of black-headed ibis T. melanocephalus were recorded in 2016, while 643 in 2017, which was more than the survey performed by Koli et al (2013a) in the same area during 2008 and 2009. In our study, the highest number of black-headed ibis T. melanocephalus was recorded in Udaipur district and lowest was in Pratapgarh during 2016, whereas in 2017,
Figure 3. Percentage of individuals sighted in different microhabitats during the survey: A, 2016; B, 2017. CF ¼ agriculture crop field; GA ¼ grazing area; IC ¼ irrigation canal; MG ¼ municipal garbage; O ¼ others; PW ¼ perennial wetland; SL ¼ sewage line; SW ¼ seasonal wetland.
the highest number was noted in Banswara and lowest in Rajsamand. On contrary, Koli et al (2013a) found the highest number of individuals for both years in Chittorgarh, while lowest in Udaipur during 2008 and in Pratapgarh during 2009. This variation in the number in both studies might be because of the difference in sampling efforts; we scanned 69 wetlands, while Koli et al (2013a) surveyed only 28 wetlands. Besides this, the difference in the number of our surveys conducted both years strongly supports frequent local migration of the species, which can be derived by irregular rainfall pattern in the study area. Microhabitat preference of black-headed ibis T. melanocephalus changed seasonally in our study. Seasonal wetlands were the most preferred habitat, likely due to that they provide optimal feeding ground in the form of the large marshy open area than perennial wetlands. Use of sewage line throughout all seasons may be because of high chironomid larvae and oligochaetes density, which is often close to vegetation or in moist soil in standing water (Frederick and Bildstein 1992; Safran et al 2000; Sundar 2006). Seasonal water level variations in different habitats may cause variations in abundance, foraging, and diet of large waterbirds owing to changes in the availability of resources (Kushlan 1981; González 1997; Sundar 2006). Therefore, few encounters in monsoon season were may be due to high water availability throughout the area (Figure 3), which increases population dispersion. Grazing area, sewage lines, and crop fields were providing supporting habitats in monsoon when marshy open
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Table 2. Nesting sites, nesting tree species, and nest site characteristics of black-headed ibis Threskiornis melanocephalus in southern Rajasthan, India. District
Nesting site
Site code
Tree species
Available trees
TH (m)
UNH (m)
LNH (m)
GBH (m)
Preferred tree canopy
DTH (m)
DTW (m)
DTR (m)
Udaipur
Dhamawadi Ekling talab Roopsagar Udaisagar Lake Sintex tiraha, (D1) Ladsar village, (D2) Padli gujreshwer, village site 1 Padli gujreshwer, Village Site 2 Padli gujreshwer, village site 3 Padli gujreshwer, village site 4 Karawara village site 1 Karawara village site 2 Dhambola Talab
U1 U2 U3 U4 D1 D2 D3 D4 D5 D6 D7 D8 D9
Acacia nilotica Acacia nilotica Prosopis juliflora Acacia nilotica Pithecellobium dulce Acacia nilotica Acacia nilotica Acacia nilotica Acacia nilotica Prosopis juliflora Acacia nilotica Tamarindus indica Acacia nilotica
AN, PJ, EG, AI, ZM AN, AI, FR PJ, AN, AI, FR AN, PS, AN, PJ, EG, AI EG, AI, MI EG, AI, MI EG, AI, MI EG, AI, MI AN, AI -
8.7 8 5 9 10.5 13.3 15 7 15 11 8 13 14
7 7.5 4.7 6.3 9 12.5 13.2 6.8 14 9.5 6.4 12.3 13
6.4 7 4.5 5 8.5 11 11.8 6 12 9 6 12 1
0.50 0.30 0.15 0.30 0.50 0.5 1 0.4 0.80 1 0.3 1 0.5
Mid canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Upper canopy Mid canopy Mid canopy Upper canopy Upper canopy
28 100 50 30 5 100 5 8 13 12 10 2 200
8 2 3 2 1500 0 50 40 5 20 0 1 0
3 90 60 70 0.5 70 0.5 1 1.5 4 7 10 500
Dungerpur
AN ¼ Acacia nilotica; AI ¼ Azadirachta indica; EG ¼ Eucalyptus globulus, MI ¼ Mangifera indica; PJ ¼ Prosopis juliflora; ZM ¼ Ziziphus mauritiana. Nest site characters: TH ¼ tree height; UNH ¼ uppermost nest height; LNH ¼ lowermost nest height; GBH ¼ girth at breast height; DTH ¼ distance to human habitation; DTW ¼ distance to water; DTR ¼ distance to road. “-” indicate no available tree.
Table 3. The number nests of black-headed ibis Threskiornis melanocephalus and communal species, recorded in different nesting colonies of southern Rajasthan, India. For site name, refer code with Table 2. Species
Scientific name
U1
U2
U3
U4
D1
D2
D3
D4
D5
D6
D7
D8
D9
Cattle egrets Great egrets Little egrets Eurasian spoonbill Asian openbill Little Cormorant Painted stork Night heron Black-headed ibis Total
Bubulcus ibis Casmerodius albus Egretta garzetta Platalea leucorodia Anastomus oscitans Phalacrocorax niger Mycteria leucocephala Nycticorax nycticorax Threskiornis melanocephalus
20 5 0 0 0 0 0 0 13 38
10 0 0 0 0 7 0 0 8 25
22 3 7 0 15 16 0 0 35 98
5 0 0 0 0 3 0 0 12 20
15 5 6 0 0 3 0 0 8 37
8 3 0 0 5 8 0 0 13 37
4 2 3 0 8 0 0 0 3 20
20 8 9 0 13 11 0 0 10 71
35 10 12 3 0 7 0 3 15 85
15 4 0 0 0 2 0 0 9 30
20 7 8 0 0 4 0 0 4 43
40 15 13 0 0 8 0 0 27 103
50 17 12 8 15 35 25 15 50 227
Table 4. Association of black-headed ibis (BHI) with other species at nesting sites. Pair (aeb)
BHI-CE BHI-GE BHI-LC BHI-LE BHI-AO BHI-ES BHI-NH BHI-PS
Number of censuses including A and B (c)
A only (a)
B only (b)
13 11 11 8 5 2 2 1
0 2 2 5 8 11 11 11
0 0 0 0 0 0 0 0
Dice’s association index 1.00 0.92 0.92 0.76 0.50 0.35 0.26 0.13
AO ¼ Asian openbill; CE ¼ cattle egret; ES ¼ European spoonbill; GE ¼ great egret; LC ¼ little cormorant; LE ¼ little egrets; NH ¼ night heron; PS ¼ painted stork.
areas around wetlands become submerged. This season is also considered the breeding season of black-headed ibis T. melanocephalus in India (Tiwari and Rahmani 1998; Gadhvi and Soni 2006), which aggregate individuals in breeding colonies and ultimately decreases birds’ encounter in open areas. In summer and winter, shallow seasonal wetlands attracted ibises possibly due to suitable shallow feeding areas in few seasonal wetlands than the monsoon. Municipal garbage along with rotten vegetable matter and carcass also provided additional feeding sites to black-headed ibis T. melanocephalus in the study area (Chaudhury and Koli 2016). Use of grazing area and crop field increased in monsoon. Grazing areas were used for resting, but in crop fields, black-headed ibis T. melanocephalus, observed along with cattle egrets during sowing, might be in search of insects as food items (per observ.). During our study, nesting of black-headed ibis T. melanocephalus was found in human habitation, near wetlands and in the islands, while most preferred nesting trees were A. nilotica and P. juliflora.
Most nests were found in the middle and upper canopy areas of trees. It seems that the species choose nesting site after careful assessment of the safety conditions along with the nearby foraging area. Since nesting colonies in unmanned areas are severely attacked by natural predators and late nesters are more prone to predatory loss of nestlings, the waterbirds usually tend to form breeding colonies near human habitations. Thorny nesting trees restrict access to ground predators such as snakes and also protect nest against storm and downpour. Patanakar (2004) reported regular black-headed ibis T. melanocephalus nesting in suburban areas, indicating its adaptability in nesting site selection. Thick canopy prevents the chick falling directly on the ground and reduces thermal stress to young ones (Dayananda and Hosetti 2009; Senma and Acharya 2010), and nesting on upper canopy height could be advantageous in alighting from a flight. In sum, southern Rajasthan is supporting a sound population of black-headed ibis T. melanocephalus. The highest number of population recorded is from Udaipur while lowest was recorded in Pratapgarh district. The species also showed seasonal variation in habitat preference. Nesting sites were recorded from two districts, and A. nilotica and P. juliflora were the most preferred nesting tree species. Conflicts of interest The authors declare that there is no conflicts of interest. Acknowledgments The authors thank Virendra Singh Bedsa, Kamlesh Ii, and Dr Anil Tripathi for assistance in fieldwork. The work is not funded by any agency.
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Please cite this article in press as: Chaudhury S, Koli VK, Population status, habitat preference, and nesting characteristics of black-headed ibis Threskiornis melanocephalus Latham, 1790 in southern Rajasthan, India, Journal of Asia-Pacific Biodiversity (2018), https://doi.org/10.1016/ j.japb.2018.01.013