Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 July 2024 | 16(7): 25495–25506
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.9003.16.7.25495-25506
#9003 | Received 29
February 2024 | Final received 09 June 2024 | Finally accepted 18 July 2024
Spatial assemblage of shorebirds
(Aves: Charadriiformes) in an altered wetland of the
southern coast of Sri Lanka
V.N. Mendis
1, E.J.A.P. Buddhi Priyankara 2,
E.G.D.P. Jayasekara 3
& W.A.D. Mahaulpatha 4
1 Faculty of Graduate Studies,
University of Sri Jayewardenepura, Gangodawila,
Nugegoda 10250, Sri Lanka.
2 Kalametiya Eco Birdwatching, 1/81, Bata Atha South, Hungama 82120, Sri
Lanka.
1,3,4 Department of Zoology, Faculty of
Applied Sciences, University of Sri Jayewardenepura, Gangodawila,
Nugegoda 10250, Sri Lanka.
1 vinurim@gmail.com, 2 buddhipriyankara1@gmail.com,
3 dulan@sjp.ac.lk, 4 mahaulpatha@sjp.ac.lk (corresponding
author)
Editor: H. Byju,
Coimbatore, Tamil Nadu, India. Date
of publication: 26 July 2024 (online & print)
Citation: Mendis, V.N., E.J.A.P.B. Priyankara,
E.G.D.P. Jayasekara & W.A.D. Mahaulpatha (2024). Spatial
assemblage of shorebirds (Aves: Charadriiformes) in
an altered wetland of the southern coast of Sri Lanka. Journal of Threatened Taxa 16(7):
25495–25506. https://doi.org/10.11609/jott.9003.16.7.25495-25506
Copyright: © Mendis et al. 2024. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use,
reproduction, and distribution of this article in any medium by providing
adequate credit to the author(s) and the source of publication.
Funding: This research was funded by the University of Sri Jayewardenepura postgraduate grant (ASP/01/RE/SCI/2022/18).
Competing interests: The authors declare no competing interests.
Author details: Vinuri Nisansa Mendis—post
graduate researcher engaged in research in the field of wildlife ecology conservation with a focus on ornithology. E.J.A.P.
Buddhi Priyankara—naturalist based in southern Sri Lanka contributing to conservation actions locally and nationally and engaging in sustainable ecotourism activities. E.G. Dulan Pathum Jayasekara—lecturer in Zoology from the University of Sri Jayewardenepura having over 10 years of experience in research in the fields of wildlife ecology and conservation, mammalogy, herpetology, population ecology and GIS and remote sensing. W.A. Dharshani Mahaulpatha—professor
in Zoology from the University of Sri Jayewardenepura having over 30 years of experience in research in the fields of wildlife ecology and conservation, population ecology, wildlife management, herpetology and ornithology.
Author contributions: All authors contributed equally to data collection, sampling and analysis, and
preparing the manuscript. The maps were prepared by E G D P Jayasekara, and the photographs were taken by V N Mendis.
Acknowledgements: We acknowledge the immense
support and guidance given by the Department of Wildlife Conservation Sri Lanka
(Permit No: WL/3/2/42/22), Department of Zoology and Faculty of Graduate
Studies of the University of Sri Jayewardenepura, and the members of the
Wildlife Circle of the University of Sri Jayewardenepura to conduct this
research successfully.
Abstract: The coastal wetlands along the
southern coast of Sri Lanka are home to a diverse array of shorebirds thriving
in their natural habitats, classified under the order Charadriiformes.
This study examines the impact of land cover changes within the Kalametiya Sanctuary, situated on the southern coast, on
the diversity, distribution, and habitat utilization of migrant and breeding
resident shorebirds. Three distinct habitat types were selected within the
study area: grassland, lagoon, and mixed mangroves. Employing Geographic
Information System (GIS) data the land cover changes of these habitats from
2002 to 2023 were analyzed using satellite imagery. Results indicated a
substantial decrease in lagoon habitat area by 70% and grassland habitat by
30%, while mixed mangrove habitat saw an increase of >90%. These changes
were attributed to anthropogenic interventions and natural events such as the
2004 Tsunami. To determine the shorebird assemblages within the study area
thriving in these changing habitats, surveys were conducted from May 2022 to
April 2023 at 30 fixed point-count stations along transects in the selected
habitat types. A total of 25 shorebird species belonging to six families were
recorded. Notable among these were the globally ‘Near Threatened’ species such
as the Black-tailed Godwit Limosa limosa and the Great Thick-knee Esacus
recurvirostris, alongside nationally threatened
species including Kentish Plover Charadrius
alexandrinus, Gull-billed Tern Gelochelidon nilotica,
and Common Tern Sterna hirundo species. The
mixed-mangrove habitat exhibited the highest shorebird abundance, with 19
species recorded, surpassing the 13 and 11 species recorded in the grassland
and lagoon habitats, respectively. Additionally, both grassland and
mixed-mangrove habitats demonstrated similar diversity indices and shared more
species in common (Shannon’s diversity index [H] = 2.17; Jaccard Similarity
Index = 0.45) compared to the lagoon habitat (H = 2.09). Despite the notable
decline in lagoon habitat cover, during the present study, it was observed that
the overall shorebird populations have been sustained within grassland and
mixed-mangrove habitats utilized for their feeding and nesting. Additionally,
over-summering migratory shorebirds were observed utilizing these habitats.
Hence, the Kalametiya sanctuary serves as a unique
setting to study the ecological resilience of migratory and breeding resident
shorebirds amidst human interventions. This research provides valuable insights
for biodiversity conservation and habitat management in the face of
human-induced alterations within ecosystems located especially along migratory
pathways of shorebird species. Both grassland and mixed-mangrove habitats
exhibited similar diversity indices and shared more species (Shannon’s diversity
index [H] = 2.17; Jaccard Similarity Index = 0.45) compared to the lagoon
habitat (H = 2.09). Despite the significant decline in lagoon habitat cover,
this study observed that overall shorebird populations have been sustained
within the grassland and mixed-mangrove habitats, which they use for feeding
and nesting. Additionally, over-summering migratory shorebirds were observed
utilizing these habitats. Thus, the Kalametiya
sanctuary serves as a unique setting for studying the ecological resilience of
migratory and breeding resident shorebirds amidst human interventions. This
research offers valuable insights for biodiversity conservation and habitat
management, particularly in ecosystems along migratory pathways of shorebird
species, in the face of human-induced alterations.
Keywords: Bird migration, Central Asian
Flyway, coastal wetland, habitat alteration, habitat utilization, land cover
changes, protected areas, wetland conservation.
INTRODUCTION
Sri Lanka serves as a major
landmass for migratory birds traversing the Central Asian Flyway (CAF). The
coastal wetlands on the island support a rich biodiversity and provide
essential ecosystem services such as maintaining ecological balance and nutrient
cycling (Basset et al. 2013; Gunatilleke et al. 2017;
Newton et al. 2018). They also play a pivotal role in connecting global
habitats by serving as a vital stopover, feeding and nesting grounds for
migrating and breeding resident avifauna, especially shorebirds of the Order Charadriiformes (Kotagama et al.
2006). Notably, coastal wetlands particularly in southern Asia are known to
offer critical habitat for threatened migratory shorebirds with decreasing
populations due to the depletion of the coastal environment (Ferreira et al.
2005; Delany et al. 2009). They are indispensable for long-distance migrant
shorebirds to replenish energy stores, feed, and rest, and for resident
shorebirds to sustain their populations through nesting sites (Pérez-Ruzafa et al. 2011; Aycock & Sims 2015; Duan et al. 2022).
Despite their importance, human
exploitation has led to threats and modifications to Sri Lanka’s coastal
wetlands over the years (Jayathilake & Chandrasekara 2015; Madarasinghe
et al. 2020b; Kodikara et al. 2023). However, studies
identify that understanding interactions with the ecology and biodiversity of
coastal wetlands in developing countries including Sri Lanka show a lack of
improvement in comparison to the well-developed regions of the world. Hence, it
is important to determine the influence of such interventions on the
biodiversity that depends on these habitats, especially for sensitive species
like shorebirds, and what measures could be taken to manage and minimize any
detrimental effects on the shorebird community.
The Kalametiya
Sanctuary, located on the southern coast of Sri Lanka, is renowned for its
biodiversity and ecological significance, serving as an avifaunal region (Ekanayake et al. 2005; Bernard et al. 2023). Encompassing
over 700 hectares, the sanctuary comprises various habitats including mangrove
swamps, lagoons, sandy shores, and grasslands, all of which support shorebird
communities (Ekanayake et al. 2005; Bernard et al.
2023). Designated as a sanctuary since 1984, it is governed by the Fauna and
Flora Protection Ordinance and the southern Province Hambantota Integrated
Coastal Zone Management Project (Jayatissa et al.
2002; Ekanayake et al. 2005; Perera
et al. 2013; Madarasinghe et al. 2020a). Scientific
research within Kalametiya sanctuary can therefore
provide valuable insights into not only avian ecology but also on coastal
wetland dynamics and ecosystem resilience of sustaining faunal communities.
Previous studies have documented the sanctuary’s floral
and fauna diversity and how various interventions, such as the Udawalawe Irrigation and Resettlement Project and the 2004
Tsunami tragedy, have altered the habitat composition within the sanctuary,
over the course of the period from 2005 to 2020 (Bambaradeniya
et al. 2005; Ekanayake et al. 2005; Madarasinghe et al. 2020a,b).
Based on the literature, one of
the main factors for good shorebird habitat is the presence of adequate
foraging sites. Effective conservation of shorebird habitats requires a
thorough understanding of the patterns of shorebirds’ spatial and temporal
utilization of habitats. This knowledge can be difficult to attain and may be
time-consuming, especially in coastal settings, since shorebirds can show
complex local movements, being very specific in their habitat requirements and
their capability of traversing long distances between preferred sites (Warnock
& Bishop 1998; Pearce-Higgins et al. 2017). Hence, to better understand
species-habitat relationships within coastal wetlands, it is imperative to
adopt a multispectral and multi-temporal data analysis approach using modern
remote sensing and GIS technologies (Albanese et al. 2012; Kaliraj
et al. 2017; Vivekananda et al. 2021). Studies such as the present research
that incorporates both on-ground field records and remote sensing analysis
could serve the purpose of achieving the intended objectives of effective
shorebird species conservation and habitat management.
Moreover, since shorebirds serve
as biological indicators of ecosystem health (Colwell 2010), conservation efforts
must focus on preserving their habitats, including wintering, feeding, and
nesting grounds (Thomas et al. 2004; Jumilawaty et
al. 2022). Yet none of the research conducted thus far has assessed shorebird
diversity, distribution, and habitat utilization in the Kalametiya
Sanctuary. This study aims to address this gap by determining shorebird
diversity, distribution, and habitat utilization in Kalametiya
Sanctuary, considering the effects of recent land cover changes, and proposing
management options, including the possibility the Sanctuary be declared as a Ramsar-protected wetland based on identified human and
natural threats.
Materials
and Methods
Study area
This study was conducted within Kalametiya Sanctuary (6.086 N, 80.936 E) situated in the
southern province of Sri Lanka. This region falls within the island’s dry zone,
receiving an average annual rainfall ranging 1,000–1,250 mm. Spanning an area
of 700 ha, the sanctuary is designated under the Fauna and Flora Protection
Ordinance (FFPO) and governed by the Department of Wildlife Conservation (DWC)
(Ekanayake et al. 2005; Perera
et al. 2013). It comprises the larger Kalametiya
lagoon and a smaller Lunama lagoon, connected by a
man-made narrow channel. For the study, three primary habitat types were
identified: grassland (G), lagoon (L), and mixed mangrove (MM), and selected
(Image 1) based on accessibility and extensive land cover availability (Ekanayake et al. 2005).
Field survey and avifaunal
sampling
Sampling was conducted from May
2022 to April 2023, employing 30-point count stations fixed along transects
(Figure 1; GPS points of point count stations given in Table 4) (Bibby et al.
1998; Ntongani & Andrew 2013) in the three
selected habitats. The point counts were fixed such that each station was
separated by the other by 50 m or greater to minimize double counting (Bibby et
al. 1998; Sutherland et al. 2012; Bernard et al. 2023) and the accessibility to
each site was available throughout the study period. ArcGIS version 10.8 (Esri, Redlands, USA) was used to overlay the fixed-point
count stations on a satellite map of the selected study area.
Two days of sampling were
allocated for each of the three months during both the bird migratory season
(October–April) and non-migratory season (May–September). Morning and evening
point counts lasting 10 minutes each were conducted within a 2–3 h window of
predicted low tide - conducted during daylight, although some shorebird
foraging occurs at night (Bibby et al. 1998), on each sampling day at each
station by pairs of observers with similar training levels. Surveys were
conducted either on foot in the grassland and mixed mangrove habitats or using
slow paddle boats in the lagoon habitat, taking measures to minimize any
disturbances to the species during the survey. Shorebirds that flew over a
point were disregarded unless they landed or took off within the point count
radius within the observation period. Standard birding equipment such as Nikon
8 × 40 Action Extreme and Nikon Monarch 10 × 42 binoculars, Vanguard Endeavor
XF 60A 15–45 x 60 spotting scope, and standard field guides (Harrison & Worfolk 2011; Hayman et al. 2011) were utilized for species
identification and recording. The observed shorebird species’ common English
names were documented, and their conservation status was later determined using
the IUCN Red List of Threatened Species and the National Red List of Birds of
Sri Lanka (Secretariat 2022).
Species richness, diversity, and
similarity
Species richness was recorded as
the number of shorebird species present in a particular habitat and season.
PAST 4.15 open-source software was used to estimate Shannon’s diversity index
(H) based on the following equation:
H = Σpi
log(ln) pi
where, pi is the
proportion (n/N) of individuals of a particular species observed (n) divided by
the total number of individuals recorded (N), while ln is the natural
log, and Σ is the sum of the calculations. Significant differences between the
seasonal diversity indices were calculated using the diversity t-test.
The Relative abundance was
computed using [(number of individuals per species/total number of individuals)
× 100%] and the Jaccard similarity index [SJ] was calculated between the
habitats by using the equation,
SJ = Sa / (Sa + Sb + Sc)
where Sa is the number
of species unique to the first habitat, Sb is the number of species
unique to the second habitat, and Sc is the number of species common
in both habitats.
Determination of habitat
alteration
Multi-spectral satellite images
from Landsat 7 (ETM+/path_141/row_56) and Landsat 8 (OLI_TIRS
sensor/path_141/row_56) missions were obtained from the United States
Geological Survey online database (https://earthexplorer.usgs.gov/). The search
aimed to find Landsat datasets with minimal cloud cover during the months of
June to August, consistent with previous studies (Jayatissa
et al. 2002; Madarasinghe et al. 2020b; Bernard et
al. 2023) to avoid months with extreme rainfall or drought conditions. The
selected images for analysis were from 07 July 2002 (Landsat 7), July 18, 2012
(Landsat 7), and 09 July 2023 (Landsat 8). This approach minimized the seasonal
impact on habitat spatial variation and allowed an unbiased evaluation of the
lagoon’s saltwater and freshwater balance, considering historical precipitation
levels in July. To address differences in resolution and image quality among
the Landsat datasets, Red and NIR (near-infrared) bands were utilized to
generate normalized difference vegetation index (NDVI) rasters
as the basis for image classification. NDVI values were calculated using the
formula: NDVI = (NIR - Red)/(NIR + Red) (Grebner et al. 2013; Pantazi et
al. 2020). Habitats were classified based on NDVI pixel values: lagoon
<0.15, grassland 0.15–0.2, other vegetation 0.2–0.25, mixed mangrove
>0.25 (Drisya & Roshni 2018). An accuracy
assessment was performed on the classified images corresponding to the selected
years and kappa coefficients were calculated using a confusion matrix
(Vivekananda et al. 2021). Ground observations as well as Google Earth images
were used for ground truthing the 2023 classified image. Google Earth images
alone were used for the ground truthing accuracy assessment of 2002 and 2012 classified
images. Therefore, the limited availability of corresponding Google Earth historical data was considered
during the Landsat image selection.
RESULTS
Species
Richness and Diversity
During the
survey, 602 individuals of 25 shorebird species belonging to six families were
recorded. A similar shorebird species diversity was recorded in the grassland
and mixed-mangrove habitats (H = 2.17) and the least diversity was recorded in
the lagoon habitat (H = 2.09) (Figures 2 & 3).
The
Black-winged Stilt Himantopus himantopus, a breeding resident shorebird with a
migrant population was the most abundant species recorded in all three habitats
during the study period. The least abundant species recorded were the
Gull-billed Tern Gelochelidon nilotica and the Whimbrel Numenius
phaeopus species (Table 1). A notable observation
was the record of over-summering populations of Common Redshank Tringa totanus and
Ruddy Turnstone Arenaria interpres species utilizing the grassland and mixed
mangrove habitats during the non-migratory season. The record of the globally
‘Near Threatened’ species Black-tailed Godwit Limosa
limosa and Great Thick-knee Esacus
recurvirostris, and nationally critically
endangered species Gull-billed Tern Gelochelidon
nilotica and Common Tern Sterna hirundo and the nationally endangered Kentish Plover Charadrius alexandrinus
within the study area highlights the overall standpoint of Kalametiya
Sanctuary to support thriving shorebird communities.
Changes in
shorebird species diversity and richness during the migratory and non-migratory
seasons depicted that most shorebirds were observed utilizing mixed mangrove
habitats than the grassland and lagoon habitats during the migratory season,
while in the non-migratory season, the highest occurrence was recorded in the
grassland habitat (Table 2). A t-test comparison of the diversity indices of
the migratory season indicates that there is a significant difference in the
diversity recorded in the mixed mangrove habitat with that of the diversity
recorded in the lagoon (t = 2.682, df = 85.52, p =
0.008) and grassland habitats (t = 2.034, df =
287.07, p = 0.0429). During the non-migratory season however, only the
diversity of shorebird species recorded in the mixed mangrove and lagoon
habitat (t = 3.132, df = 168.94, p = 0.002)
significantly differed.
Changes in
land cover within the study area
The spatio-temporal change in land cover within the study area
for the past two decades is depicted in the maps (Figure 4) generated from
satellite data. Overall, the lagoon area has decreased by 69.94% and the
grassland area has decreased by 30.75%. However, the area of mixed mangroves
within the study site has increased by 93% from 2002 to 2023 (Table 3). The
accuracy assessment was performed for 2002, 2013, and 2023 land cover maps and
an overall kappa statistic of 0.741, 0.754, and 0.736 were computed for each
respectively.
DISCUSSION
The global decline in shorebird
populations is of growing concern, highlighting the need for dedicated efforts
towards their conservation and sustainable management (Clemens et al. 2010; Aarif et al. 2014). Coastal wetlands, particularly in Asia
which support such migratory and breeding resident shorebird species, even
though considered the most productive of the many types of wetlands categorized
by the Ramsar Convention (https://rsis.ramsar.org/),
are affected by exponential population growth and imbalances in demand-supply
interactions arising mostly due to urban developments. Shorebirds are
considered to play a significant role in maintaining the health of the
environment they utilize (Colwell 2010) and therefore, the protection of their
stopover resources within coastal wetlands could pave the way for the sustaining
of both shorebird communities and the wetland habitats (Myers et al. 1987;
Skagen & Knopf 1994). Considering the above concerns, it is evident that
Sri Lanka’s coastal wetlands present an understudied yet ecologically
significant arena for investigating the dynamics of shorebird communities
amidst continuing alterations in the southern Asian region. Hence, the present
study conducted in the Kalametiya Sanctuary, located
in southern Sri Lanka, which assesses the shorebird diversity, distribution,
and habitat utilization considering habitat cover changes that have occurred
over past decades, provides a reference framework for implementing timely
species conservation and habitat management strategies.
During the present research, a total of 25
shorebird species belonging to the order Charadriiformes
were documented, of which 60% can be classified as migratory species, 20% as
breeding residents, and the remainder as breeding resident species with a
migrant population. In contrast, a recent study by Bernard et al. (2023)
reported only 10 shorebird species, while a previous biodiversity profile by Ekanayake et al. (2005) documented 38 species. However, it
is important to note that the 2005 survey considered the entire Kalametiya-Lunama sanctuary area, whereas the present
research focused specifically on habitats adjoining the Kalametiya
lagoon. Further, the species that were recorded in the 2005 survey that were
not recorded in the present research are some of the rare and uncommon migrant
shorebird species such as the Ruff Calidris
pugnax and Long-toed Stint Calidris
subminuta and some of the uncommon migrant tern
species such as the Saunders’s Tern Sternula
saundersi, Great Crested Tern Thalasseus
bergii, and Lesser Crested Tern Thalasseus bengalensis,
which have been found utilizing mostly the brackish lagoon water habitat within
the entire Kalametiya-Lunama sanctuary area.
Consequently, direct comparisons of species richness values between studies are
not feasible due to differences in study area delineation. The demarcated study
area of the present study was chosen to assess how changes in land cover within
the Kalametiya lagoon and surrounding habitats have
impacted the diversity and habitat utilization of shorebirds, considering the
proportional area of the sanctuary. Further studies in the Lunama
lagoon area to supplement the present study could be suggested to follow a
comparative approach in identifying the shorebird habitat utilization within
the larger sanctuary area post two decades since the last published
biodiversity profile (Ekanayake et al. 2005).
Sanctuaries play a crucial role
in supporting biodiversity, albeit often subjected to regulated human
interventions (Green 1990). Over the past decades, Kalametiya
Sanctuary has undergone alterations, necessitating an understanding of the
degree of habitat cover change and its impact on long-distance migrant and
breeding resident shorebird species. Hence, the study analyzed satellite
imagery data alongside spatial assemblage data of shorebirds utilizing the Kalametiya Lagoon and surrounding habitats with the
intention of assessing the present conditions within the sanctuary. The
findings revealed a significant decrease of over 69% in the lagoon area since
2002, a notable alteration that could potentially change the species
composition within the sanctuary. Yet, this decrease in the lagoon area hasn’t
led to a drastic decline or a total displacement of shorebird communities.
Based on the results of the present study, several reasons for this phenomenon
can be proposed.
Studies identify that shorebirds
feed and roost within the shallows of a wetland having water depths of less
than 30cm, where prey availability and accessibility are mediated by their leg
and bill lengths, or on the shores of wetland clusters during low tides,
providing them chances with abundant prey (Zwarts
& Wanink 1993; Bellio
& Kingsford 2013). Hence, shorebirds continuing to sustain within the
selected study area is reflected by the study results which show that their
most utilized feeding grounds were the mixed mangrove and grassland habitats,
recording shallower water depths (less than 30 cm) which match their bill
length and leg heights, making these areas preferable over deeper lagoon
waters.
Additionally, breeding resident
shorebirds such as the Black-winged Stilts (Ashoori
2011) and Red-wattled Lapwings (Hart et al. 2002;
Arya et al. 2023) construct their nests in grassy areas or abandoned
agricultural lands using dung, mud, and decayed plant materials, unlike waterbirds that prefer aquatic vegetation for nesting.
Therefore, the decrease in the lagoon area doesn’t significantly impact the
nesting behaviors of these shorebirds. The nesting sites also contribute to the
notable species diversity observed in the grassland habitat during the non-migratory
season. Furthermore, during the non-migratory season, coinciding with the dry
spell in the study area, the drying up of mixed mangrove habitats reduces
invertebrate food sources for shorebirds. In the grassland habitat where cattle
grazing activities occur, the soil is disturbed, exposing land invertebrates
such as snails and soft annelids, which serve as a vital food source for
nesting parents and newly hatched shorebirds. However, such agricultural
interventions contribute both positively and negatively to shorebird habitat
utilization, and if not managed can lead to detrimental impacts.
Despite past recommendations for
cattle grazing to be limited to demarcated buffer zones (Ekanayake
et al. 2005), herds were observed in sensitive mixed mangrove and grassland
habitats, risking nest trampling (Hart et al. 2002) and disturbing shorebird
feeding grounds. A trampled nest of each of Red-wattled
Lapwing and Black-winged Stilt were recorded during the present study. It is
encouraged to conduct further research to actively monitor and quantify
trampling rates of shorebird nests and highlight the need for the demarcation
of grazing buffer zones within the Sanctuary.
The loss of wintering grounds in
southern Asia for long distant migratory shorebirds due to coastal developments
and habitat loss has posed a significant threat over the past years (Aarif et al. 2014; Byju et al
2023), especially to over-summering populations of shorebird species including
the Common Redshank and Ruddy Turnstone (Aarif et al.
2020) which were recorded during the present study in the Kalametiya
Sanctuary. Conservation of their over-summering habitats becomes crucial for
successful population recruitment of these species into migratory counterparts
in a consequent season or provides conditions supporting them to adapt and
withstand changes beyond their home grounds. Moreover, habitat alterations
following the 2004 Tsunami (Bambaradeniya et al.
2005; Perera et al. 2013; Madarasinghe
et al. 2020a), the irrigation project bringing in more siltation into the
lagoon (Madarasinghe et al. 2020b; Kodikara et al. 2023) and the recent breakwaters built in
the Kalametiya fishing harbor, have impacted the
ecosystem. Effective management actions are essential to regulate the
environment for wildlife and humans. Despite past recommendations (Ekanayake et al. 2005) the present study notes continued
habitat depletion due to inadequate intervention. This underscores the urgent
need for enhanced conservation efforts to protect these vital habitats and their
biodiversity.
Kalametiya Sanctuary sustains local
livelihoods through fisheries and cattle farming (Ekanayake
et al. 2005) and promotes eco-tourism with peaceful paddle boat rides dedicated
to birdwatching. However, despite the numerous services the coastal wetland
provides to maintain a healthy and productive ecosystem, it is evident that
human interventions like habitat mismanagement, over-exploitation of resources,
negligence, and uncontrolled waste disposal have disrupted the human-wildlife
coexistence, especially in terms of the sustainability of thriving populations
like shorebirds that bring not only ecological but also economical values using eco-tourism, habitat upliftment and
food web balances within their utilized habitats. Therefore, advocating for
heightened public awareness and community engagement in sustainable practices
of living is recommended to safeguard the sanctuary for future generations.
Awareness campaigns among the local fisheries and farming communities on the
effects of mismanaged waste disposal affecting both human health utilizing
contaminants, and the health of the wetland mangroves that prevent coastal
erosion, effective ways of reducing the risk of nest trampling and disturbances
to the mixed mangroves by adhering to demarcated grazing buffer zones are some
of the ground level initiatives that can be proposed to assist shorebird
species conservation and sustainable coastal wetland habitat management
implications. Further studies that identify the impacts of microplastic contamination
similar to the study conducted by Luna et al. (2022) which found microplastics
in nests of Black-winged Stilts in a Biosphere Reserve in Spain could
comprehend to the present study in enhancing shorebird nesting habitat
conservation. The year 2024 World Wetland Day theme, “Wetlands and Human
Wellbeing,” offers an opportune moment for initiating conservation efforts in
the coastal wetland habitat of Kalametiya Sanctuary.
Since the shorebird ecology and
causes and drivers for population decline in the CAF are less explored (Mundkur & Selvaraj 2023) research such as the present
study supplements to identification of human interactions that affect the
shorebird assemblage and their habitat utilization within coastal wetlands
along the CAF and what are the timely conservation strategies that can be newly
implemented and what existing strategies can be improved for better results in
future. The present study, alongside previous research, suggests the potential
declaration of the sanctuary as a Ramsar site due to
its global conservation significance, providing crucial habitats for long-
distant migrant shorebirds, threatened shorebirds, and over-summering shorebird
species. Moreover, it sheds light on the impacts of land cover and land use
changes on biodiversity in this altered coastal wetland, providing valuable
insights for authorities and communities to recognize Kalametiya
Sanctuary as a vital hub for biodiversity conservation and environmental
sustainability in Sri Lanka.
CONCLUSION
The present study highlights the
resilience of Kalametiya Sanctuary in supporting both
migratory and breeding resident shorebird species despite ongoing habitat
alterations over the past two decades. A survey conducted covering both
migratory and non-migratory seasons recorded 25 shorebird species from six
families, including globally and nationally threatened species. Land cover
changes were assessed using satellite imagery, achieving acceptable accuracy
rates exceeding 70% for each assessment year. Encouragingly, the study found
that the present status of the habitats did not adversely affect migratory and
breeding resident shorebirds, avoiding a wipe out of the species from the
habitats. Over-summering species were also found utilizing the habitats. However,
proactive management and conservation efforts are crucial to ensure the
continued thriving of shorebird populations and to prevent further habitat
depletion. Overall, this research underscores the significance of conserving
altered coastal wetlands to maintain vital stopover and over-summering sites,
especially in the southern Asian region along the CAF, while promoting
sustainable livelihoods within and surrounding the sanctuary.
Table 1. Shorebird species of Order Charadriiformes that were recorded during the study period
in the selected three habitats.
|
Family |
Scientific name |
Common name |
GCS (2021) |
NCS (2021) |
Phenological
status |
Relative
abundance (%) |
Habitat |
|
Burhinidae |
Esacus recurvirostris (Cuvier, 1829) |
Great Thick-knee |
NT |
LC |
R |
3.99 |
G/ L/ MM |
|
Burhinus indicus (Salvadori,
1865) |
Indian Thick-knee |
LC |
LC |
R |
1.66 |
G |
|
|
Charadriidae |
Charadrius mongolus (Pallas, 1776) |
Lesser Sand Plover |
LC |
- |
M |
8.80 |
G/ MM |
|
Charadrius leschenaultia (Lesson, 1826) |
Greater Sand Plover |
LC |
- |
M |
0.83 |
G/ MM |
|
|
Pluvialis fulva (Gmelin,
1789) |
Pacific Golden Plover |
LC |
- |
M |
2.82 |
G/ MM |
|
|
Charadrius alexandrinus (Linnaeus, 1758) |
Kentish Plover |
LC |
EN |
R / M |
1.16 |
G |
|
|
Pluvialis squatarola (Linnaeus, 1758) |
Grey Plover |
LC |
- |
M |
0.83 |
G/ MM |
|
|
Vanellus indicus (Boddaert,
1783) |
Red-wattled
Lapwing |
LC |
LC |
R |
12.62 |
G/ L/ MM |
|
|
Vanellus malabaricus (Boddaert,
1783) |
Yellow-wattled
Lapwing |
LC |
LC |
R |
3.16 |
G |
|
|
Jacanidae |
Hydrophasianus chirurgus (Scopoli,
1786) |
Pheasant-tailed Jacana |
LC |
LC |
R |
2.33 |
L |
|
Laridae |
Chlidonias hybrida (Pallas, 1811) |
Whiskered-Tern |
LC |
- |
M |
3.49 |
L/ MM |
|
Gelochelidon nilotica (Gmelin,
1789) |
Gull-billed Tern |
LC |
CR |
R / M |
0.49 |
L |
|
|
Sterna hirundo (Linnaeus, 1758) |
Common Tern |
LC |
CR |
R / M |
1.16 |
L |
|
|
Sternula albifrons (Pallas, 1764) |
Little Tern |
LC |
VU |
R / M |
1.83 |
L/ MM |
|
|
Recurvirostridae |
Himantopus himantopus (Linnaeus, 1758) |
Black Winged Stilt |
LC |
LC |
R / M |
24.25 |
G/ L/ MM |
|
Scolopacidae |
Tringa totanus (Linnaeus, 1758) |
Common Redshank |
LC |
- |
M |
16.45 |
G/ L/ MM |
|
Tringa nebularia (Gunnerus,
1767) |
Common Greenshank |
LC |
- |
M |
0.33 |
MM |
|
|
Tringa stagnatilis (Bechstein,
1803) |
Marsh Sandpiper |
LC |
- |
M |
0.49 |
L/ MM |
|
|
Tringa glareola (Linnaeus, 1758) |
Wood Sandpiper |
LC |
- |
M |
0.83 |
MM |
|
|
Actitis hypoleucos (Linnaeus, 1758) |
Common Sandpiper |
LC |
- |
M |
1.33 |
L/ MM |
|
|
Arenaria interpres (Linnaeus, 1758) |
Ruddy Turnstone |
LC |
- |
M |
4.98 |
G/ MM |
|
|
Calidris minuta (Leisler, 1812) |
Little Stint |
LC |
- |
M |
1.66 |
MM |
|
|
Numenius phaeopus (Linnaeus, 1758) |
Whimbrel |
LC |
- |
M |
0.49 |
MM |
|
|
Limosa limosa (Linnaeus, 1758) |
Black-tailed Godwit |
NT |
- |
M |
0.83 |
MM |
|
|
Gallinago stenura (Bonaparte, 1830) |
Pintail Snipe |
LC |
- |
M |
1.16 |
G/ MM |
M—Migrant
| R—Resident | GCS—Global Conservation Status | NCS— National Conservation
Status.
Table 2. Shorebird species diversity
comparison of the migratory and non-migratory seasons in the three habitats.
|
|
Non-migratory
season |
Migratory
season |
||||
|
Grassland |
Lagoon |
Mixed
mangrove |
Grassland |
Lagoon |
Mixed
mangrove |
|
|
Shannon’s diversity index (H) |
2.055 |
1.919 |
1.472 |
2.207 |
2.079 |
2.429 |
|
Evenness |
0.7811 |
0.757 |
0.436 |
0.699 |
0.799 |
0.630 |
|
Richness |
10 |
9 |
10 |
13 |
10 |
18 |
|
Total number of individuals (N) |
89 |
68 |
101 |
126 |
48 |
170 |
Table 3. Land cover change (%) of the
habitats in the study area over the period of 2002–2023.
|
|
2002 |
2013 |
2023 |
Change
(2002–2023) |
% change |
|
Lagoon |
13.7 |
6.5 |
4.1 |
-9.6 |
-69.9373 |
|
Grasslands |
24.6 |
22.7 |
17.0 |
-7.6 |
-30.7483 |
|
Other vegetation |
30.0 |
24.0 |
17.7 |
-12.3 |
-40.9414 |
|
Mixed mangroves |
31.6 |
46.8 |
61.1 |
29.5 |
93.19583 |
Table 4. Point count stations fixed along
transects in the three selected habitats within the study area.
|
Grassland
T1 |
Lagoon T2 |
Mixed
mangrove T3 |
||||||
|
Point count
station |
Longitude |
Latitude |
Point count
station |
Longitude |
Latitude |
Point count
station |
Longitude |
Latitude |
|
P1i |
80.937 |
6.082 |
P1ii |
80.936 |
6.080 |
P1iii |
80.935 |
6.083 |
|
P2i |
80.938 |
6.083 |
P2ii |
80.935 |
6.081 |
P2iii |
80.936 |
6.084 |
|
P3i |
80.940 |
6.084 |
P3ii |
80.935 |
6.081 |
P3iii |
80.938 |
6.086 |
|
P4i |
80.940 |
6.084 |
P4ii |
80.935 |
6.082 |
P4iii |
80.940 |
6.087 |
|
P5i |
80.941 |
6.084 |
P5ii |
80.935 |
6.083 |
P5iii |
80.943 |
6.088 |
|
P6i |
80.942 |
6.085 |
P6ii |
80.935 |
6.084 |
P6iii |
80.944 |
6.088 |
|
P7i |
80.943 |
6.085 |
P7ii |
80.935 |
6.085 |
P7iii |
80.945 |
6.090 |
|
P8i |
80.944 |
6.086 |
P8ii |
80.935 |
6.087 |
P8iii |
80.947 |
6.090 |
|
P9i |
80.945 |
6.087 |
P9ii |
80.935 |
6.088 |
P9iii |
80.947 |
6.092 |
|
P10i |
80.946 |
6.087 |
P10ii |
80.935 |
6.089 |
P10iii |
80.947 |
6.093 |
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