Foraging Ecology of Twelve Ardeid Species at Lungh Lake, Pakistan
Muhammad Nawaz Rajpar1, Munir Ozturk2, Salih Gucel3 and Iris Charalambidou4*
1Department of Forestry, Faculty of Life Sciences, Shaheed Benazir Bhutto University Sheringal, Dir (Upper), Khyber Pakhtunkhwa, Pakistan.
2Centre for Environmental Research, Ege University, Izmir, Turkey.
3Centre for Environmental Studies, Near East University, Nicosia, Cyprus.
4Department of Life Sciences, School of Life and Health Sciences, University of Nicosia, Nicosia, Cyprus.
ABSTRACT
Ardeids are wading birds that play an important role in aquatic habitats, i.e., they are pest-control agents of amphibians, insects and small rodents and serve as bioindicators. They face overwhelming threats such as water pollution due to organic and inorganic contaminations that often are released from industrial plants, domestic sewage and mining effluents discharged into the waterways, habitat loss and degradation resulting from the conversion of lakes into agricultural fields, as well as water diversion and abstraction for agricultural purposes Observations on foraging ecology, habitat choices and prey items of Ardeids were conducted monthly, from January 2018 to December 2019. Birds were observed with a spotting scope (V 20x80mm), binoculars (10x50mm) and direct observations. A total of 2420 observations of 12 species were recorded and 13 behaviours documented. The little egret (Egretta garzetta) (18.8±6.5 individuals/ha), intermediate egret (Mesophoyx intermedia) (15.8±5.6 individuals/ha) and eastern cattle egret (Bubulcus coromandus) (14.0±5.6 individuals/ha) were the most abundant species. The cinnamon bittern (Ixobrychus cinnamomeus) (3.0±2.5 individuals/ha) and black–crowned night–heron (Nycticorax nycticorax) (2.7±3.1 individuals/ha) the least abundant. All Ardeids foraged in habitats where water was present. Only the eastern cattle egret foraged in grassy areas and adjacent agriculture fields. All ardeids fed on a variety of prey. All species utilized at least seven foraging techniques, only the black–crowned night–heron used three techniques. The little egret (45 probes/minute) and eastern cattle egret (35 probes/minute) were the most active foragers. Together with the intermediate egret they were the most aggressive species. Overall, ardeids use a variety of foraging techniques, and vary in food selection and habitat selection. Our results illustrate the diversity of Ardeid species utilizing Lungh Lake, Qambar Shahdadkot District, near Larkana, Sindh Province, Pakistan. In conclusion, Ardeids employed a broad variety of foraging tactics when capturing food items and exploiting various foraging grounds where prey items concentrated particularly in shallow waters, lake edges, and thick matts of sedges.
Article Information
Received 11 May 2025
Revised 25 October 2025
Accepted 08 November 2025
Available online 13 April 2026
(early access)
Published 30 July 2026
Authors’ Contribution
Research data were collected and analyzed by RMN. OM wrote the manuscript. GS reviewed the manuscript, and CI edited and corrected the manuscript.
Key words
Habitat, Waders, Behavior, Trophic structure, Water, Lungh Lake
DOI: https://dx.doi.org/10.17582/journal.pjz/20250511150332
* Corresponding author: [email protected]
0030-9923/2026/0005-2147 $ 9.00/0
Copyright 2026 by the authors. Licensee Zoological Society of Pakistan.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
INTRODUCTION
In recent decades the world has undergone substantial social, economic, and ecological changes (O’Connell, 2000). Wetlands have been lost or degraded while the remaining ones are under heavy pressure due to human interventions. Habitat loss and degradation, water pollution, excessive hunting, introduction of invasive species, and climate change (Woodward and Wui, 2001; Kingsford and Thomas, 2004; Wei et al., 2008) have resulted in a 23% decline of water bird populations and 19% becoming threatened (Birdlife International, 2017; Wang et al., 2018). Pakistan possesses a variety of wetlands, despite its predominantly arid and semi-arid topography (Rais et al., 2011). Many climatic and vegetation zones within a relatively small area (IUCN, 1989) have resulted in different types of wetland systems, with more than 225 wetlands in Pakistan (Ali et al., 2018).
Foraging is one of the most essential activities of avian behavior, through which birds obtain food for their survival and reproduction. Most avian species spend most or part of their time searching for food (Morrison et al., 1990). Ardeids, e.g., egrets, bitterns, and herons, forage using a variety of methods to catch prey (Kushlan and Hancock, 2005). Foraging is an aggregation activity as they utilize similar food resources and aquatic habitats known as a guild or functional group. Ardeids employ up to 41 foraging techniques (Frederick, 2002; Kushlan and Hancock, 2005; McKilligan, 2005) and utilize different wetland habitats, such as rice fields, freshwater marshes, salt marshes, rivers and estuaries (e.g. Kazantzidis and Goutner, 1996; Custer et al., 2004). The foraging technique may vary depending on the species and habitat, the availability and richness of food resources, structure and composition of vegetation, and water depth (Kushlan and Hancock, 2005). Ardeids may use different prey–capturing strategies to catch their prey. For example, lean forward and wait motionless, stand and wait, walk slowly, walk quickly, follow prey by running, open wing feeding, double wing feeding, food snatching, bill vibrating or tongue flicking, using rafts/perches, wing flicking, foot stirring or shuffling or raking, hovering or skimming over the surface, dipping, legs trailing in water and foot dragging or paddling to lure the fish, jumping and hopping (Kushlan, 2011; Aboushiba et al., 2013). Dimalexis et al. (1997) determined the strike rate, foraging efforts per minute, foraging efficiency, and prey capture success rate among three ardeid species, e.g., grey herons (Ardea cinerea), great egrets (Ardea alba), and little egrets (Egretta garzetta) in Greek wetlands and found that they used walk slowly, walk quickly, and stand and wait foraging tactics to catch prey along shallow waters and wetlands. The same results were also reported by Nefla and Nouira (2016) in herons inhabiting Ichkeul National Park, Tunisia. Similarly, Modal and Maheswaran (2021) analyzed the foraging ecology of the white-bellied heron (Ardea insignis) in Namdapha tiger reserve, Arunachal Pradesh, India and found that strikes/hour, caught/hour, and capture efficacy varied in the egret species.
Interspecific foraging strategies are the most prevalent way for ardeids to capture and consume their prey. This study is based on the specific research hypothesis that ardeids don’t overlap in trophic structures while exploiting the food resources available to them. Using the niche partitioning hypothesis, the study examined whether ardeids exploiting Lungh Lake in Larkana varied in their prey capture and food consumption. Lungh Lake is a natural lake, designated as a Wildlife Sanctuary since 1984 (Ali-Brohi and Rasheed, 2016). It is located on the Indus Fly Zone that serves as a middle Asian flying route for migratory birds and is connected to West Asian and East African flying routes (Umar et al., 2018). As such, it is a refuge for migratory waterfowl in the wintering months, acting as a stopover for around 20,000 water birds, migrating from Siberia on their way to India (Ali-Brohi and Rasheed, 2016). Land–use and land cover changes at the lake and its surrounding areas from 1988 to 2020 show significant shrinkage of the lake area due to agriculture expansion, and an increase in vegetation by 72%. Therefore, there is an urgent need for the development of a management plan for the lake (Ditta et al., 2021). Moreover, there is a scarcity of studies on water birds utilizing the lake. The goal of this study was to ascertain the differences in foraging ecology among Ardeid species to inform conservation strategies. We investigated the choice of habitats, prey items and foraging techniques used by the birds and envisage that this information will assist in the conservation of the lake and its biodiversity.
MATERIALS AND METHODS
Study area
Lungh Lake (680 03’ E, 270 30’ N; Elevation: ~54 meters above sea level) is located at Qambar Shahdadkot District, near Larkana, in Sindh Province, Pakistan (Fig. 1). It covers an area of 39.66 ha (3.96 km2) and is dominated by aquatic vegetation such as cattail (Typha angustifolia), giant reed/elephant grass (Arundo donax), common/soft rush (Juncus effusus), coontail/hornwort (Ceratophyllum demersum) and common reed (Phragmites australis). The lake edges are covered by gum arabic/babul/kikar trees (Vachella nilotica), Indian jujube/beri (Zizyphus mauritiana), athel tamarix/ghaz/farash (Tamarix aphylla), and twigy shrub/lai (Tamarix dioica). The wetland is surrounded by agricultural fields and human settlements. The lake can be divided into three habitat types: (1) open water with Typha and Juncus on the edges, (2) swampy areas dominated by Tamarix and (3) surrounding rice fields with predominant Juncus sp. (Ali-Brohi and Rasheed, 2016). The microclimatic conditions vary throughout the year; temperatures range from 2.2 oC to 48.5 oC. The summer season lasts for four months (from April to July) and winter lasts three months (from December to February). The relative humidity ranges from 37% to 85% and the mean annual rainfall is 178 mm/year during the monsoon season (Rajpar et al., 2022).
Foraging behavior
Field observations of the foraging behavior of Ardeid species were documented using a spotting scope (Vanguard Platinum; 20 x 80mm), binoculars (Olympus; 10 x50mm) and direct observations, depending on visibility. The area was scanned and the Ardeid species were identified and counted. Suitable locations were selected along the wetland edges for the observations. Foraging behavior was recorded on an hourly basis, from 0700 to 1800 hours, to identify daily activity patterns. The foraging behavior of twelve Ardeid species was recorded for 2880 hours (i.e., 10 hours/day, 12 days/month, and 24 months). For each
day, we focused on recording the behavior of one species chosen randomly. The Ardeid species were classified as either solitary (preying alone) or gregarious (foraging with other species). Capturing of food was referred to as prey occurrences, the type of food consumed was referred to as prey selection frequency, and the preferred site for foraging was referred to as habitat preference. Observations were recorded monthly, from January 2018 to December 2019. The methodology is described in detail by Kushlan (2007), Choi et al. (2008), and Sharah et al. (2008). Foraging behavior of the ardeids was divided into 13 categories based on major food selection, tactics employed while foraging and habitat preference as suggested by Degraaf et al. (1985), Ehrlick et al. (1988) and Thorngate et al. (2006).
Statistical analysis
Relative frequency is the percentage of each behavior used by ardeids, food consumption, and movement at Lungh Lake while exploiting food resources using a wide range of techniques (Anderson, 2017). The relative frequency of each bird species was calculated by a given formula;
Where, Isi = total number of individuals of each identified bird species, /∑Nsi = total number of detected bird species in the study area.
In addition, the relative frequency movements, food consumption, and foraging behavior of ardeids was compared using a Kruskal-Wallis Nonparametric H test and Tukey’s Honestly Significant Difference (HSD) test using Statistics 8.1 Analytical Software; Version 8.1 (Steel and Torrie, 1997; McGraw-Hill, 2008).
The Kruskal-Wallis H Test was used to compare the foraging techniques, movement behavior, food preference and habitat selection among the Ardeid species. It was performed according to the formula;
Where, “n” = the total number of observations, “R” = is the sum of the ranks of each species, and “ni” = number of each detected items.
RESULTS
Ardeid abundance
In total, 2420 observations from 12 Ardeid species were recorded. The little egret (18.8 ± 6.5 individuals/ha), intermediate egret (15.8 ± 5.6 individuals/ha) and Eastern cattle egret (14.0 ± 5.6 individuals/ha) were the most abundant species. The cinnamon bittern (3.0 ± 2.5 individuals/ha) and black–crowned night–heron (2.7 ± 3.1 individuals/ha) the least abundant (Table I).
Table I. Population size (mean ± SD) and number of foraging observations of 12 Ardeid species recorded monthly (Jan 2018-Dec 2019) at Lungh Lake, Pakistan.
|
Scientific name (Common name) |
Population Mean ± SD |
Number of foraging observations |
|
Egretta garzeta (Little egret) |
18.8 ± 6.5 |
452 |
|
Mesophoyx intermedia (Intermediate egret) |
15.8 ± 5.6 |
380 |
|
Bubulcus coromandus (Eastern cattle egret) |
14.0 ± 5.6 |
338 |
|
Ardea alba (Great egret) |
12.5 ± 6.6 |
305 |
|
Ardeola speciosa (Javan pond heron) |
8.9 ± 4.3 |
214 |
|
Butorides striata (Striated heron) |
6.5 ± 3.7 |
155 |
|
Ardeola grayii (Indian pond heron) |
5.3 ± 3.2 |
127 |
|
Ardea purpurea (Purple heron) |
5.1 ± 3.3 |
123 |
|
Ardea cinerea (Grey heron) |
4.4 ± 3.1 |
105 |
|
Ardeola bacchus (Chinese pond heron) |
3.6 ± 3.1 |
86 |
|
Ixobrychus cinnamomeus (Cinnamon bittern) |
3.0 ± 2.5 |
72 |
|
Nycticorax nycticorax (Black-crowned night heron) |
2.7 ± 3.1 |
63 |
|
Total observations |
2420 |
|
Foraging observations
Out of the 12 Ardeid species, eight are solitary foragers and four are gregarious feeders. Most species are resident and partial migrants, except for the striated heron, that is the only migrant, and the Javan pond heron and Indian pond heron, are exclusively residents (Table II). Food selection and consumption among the ardeids varied, with each species consuming a variety of items. Notably, fishes (20.9%) were the most preferred food item, followed by frogs (12.3%), grasshoppers (10.2%), beetles (9.2%), water striders (8.3%) and flies (6.6%); whereas rodents (0.8%), salamanders (0.7%), and snakes (0.3%) were occasionally eaten.
Furthermore, based on the food capturing success rate, little egrets and great egrets are the most prevalent species that consume a wide variety of foods. However, the black-crowned night heron mainly consumes fishes, reptiles and amphibians. All ardeids foraged in a variety of habitats where water was present. Eastern cattle egrets are the only species that exploited grassy areas and adjacent agriculture fields instead of water.
Using the Kruskal–Wallis non–parametric one-way analysis of variance (ANOVA) a significant difference in the food consumption of the 12 Ardeid species was found; F15,191= 27.00, p < 0.05. There were seven groups (A, B, C, D, E, F, and G) with means that differed significantly from each other (Table III).
Foraging techniques
All Ardeid species used a combination of 13 foraging techniques, i.e. behavior/activities, while foraging for food (Tables IV, V). All species utilized at least seven techniques, apart from the black–crowned night–heron that used only three techniques, i.e., lean and wait (30.2%), stand and wait (52.4%) and stand and feed (17.4%). The black–crowned night–heron and the purple heron never chased their prey but waited for the prey to come close to them. The little egret was the most active forager, using prey chasing (14.6%), toe shuffling (18.0%), and walking quickly (12.8%) more often than the other heron species. Five species, the great egret, striated heron, black–crowned night–heron, cinnamon bittern and Javan pond heron, never used the wing flick behavior. Notably, the little egret was the only species that used toe–shuffled, and the Eastern cattle egret the only species that used gleaning. Four species never exhibited aggressive behavior, i.e., the black–crowned night–heron, cinnamon bittern, Indian pond heron and Javan pond heron.
Food snatching
Food snatching, i.e. stealing food from other individuals (Table V), was recorded separately from aggressive behavior, i.e. fighting for territory or food acquisition (Table IV). The Eastern cattle egret (16 %), little egret (14.6%) and intermediate egret (9.8%) exhibited the highest food snatching behavior (Table V) and were also among the most aggressive species (Table IV). The black–crowned night–heron, cinnamon bittern and striated heron avoided food snatching altogether (Table V).
Table III. Kruskal–Wallis pairwise comparisons test of observations by habitat.
|
Name of food item |
Mean value |
Homogenous group |
|
Fishes |
181.79 |
A |
|
Frogs |
159.25 |
AB |
|
Grasshoppers |
141.75 |
ABC |
|
Water striders |
134.67 |
ABCD |
|
Beetles |
133.67 |
ABCD |
|
Snails |
109.25 |
ABCDE |
|
Flies |
107.67 |
ABCDEF |
|
Backswimmers |
105.79 |
ABCDEF |
|
Earthworms |
99.208 |
BCDEF |
|
Grass bug |
92.917 |
BCDEFG |
|
Sedge moths |
77.750 |
CDEFG |
|
Damsel bugs |
62.958 |
CDEFG |
|
Water boatman |
57.538 |
DEFG |
|
Rodents |
32.875 |
EFG |
|
Salamanders |
28.875 |
FG |
|
Snake |
18.000 |
G |
Alpha value, 0.05; Critical value, 2.638; Critical value for comparison, 80.067.
Food probing
The frequency of food probing, i.e. the number of times an individual bird probed the water with their bill to capture food, differed among species. The little egret (45 probes/m) and Eastern cattle egret (35 probes/m) were the most active foragers. In contrast, the purple heron (4 probes/m), cinnamon bittern (4 probes/m) and striated heron (2 probes/m) rarely foraged through probing (Table V).
Using the Kruskal–Wallis non–parametric one-way analysis of variance (ANOVA) a significant difference in foraging techniques was detected; F10, 131 = 20.60, p < 0.05. There were three (A, B, and C) with means that were not significantly different from each other (Table VI).
DISCUSSION
In this study, 12 of the 18 Ardeid species found in Pakistan (Mosvi et al., 2019), were observed at Lungh Lake, Qambar Shahdadkot District, near Larkana, Sindh Province. The little egret, intermediate egret and Eastern cattle egret were the most abundant species while the cinnamon bittern and black–crowned night–heron were the least abundant. We have shown that ardeids employ a variety of foraging behaviors, which is in agreement with other studies (e.g. Aboushiba et al., 2013; Kasprzykowski and Golawski, 2024). Each species has its own usual behaviours, but in addition can use others to catch abundant or easily taken prey (Voisin, 2010). In our study, great egret, purple heron, grey heron, pond heron, cinnamon bittern and black-crowned night-heron, were solitary foragers. In contrast, little egret, intermediate egret, and Eastern cattle egret
Table V. Food snatching and food probing employed by 12 Ardeid species observed monthly (Jan 2018-Dec 2019) at Lungh Lake, Pakistan.
|
Scientific name |
N |
Food snatching (%) |
Probing/minute |
|
Egretta garzeta |
233 |
14.6% |
45/m |
|
Mesophoyx intermedia |
111 |
9.8% |
18/m |
|
Bubulcus coromandus |
301 |
16.0% |
35/m |
|
Ardea alba |
189 |
2.2% |
8/m |
|
Ardeola speciosa |
72 |
6.5% |
6/m |
|
Butorides striata |
107 |
0 |
2/m |
|
Ardeola grayii |
256 |
6.8% |
19/m |
|
Ardea purpurea |
73 |
4.8% |
4/m |
|
Ardea cinerea |
50 |
8.2% |
9/m |
|
Ardeola bacchus |
86 |
2.3% |
22/m |
|
Ixobrychus cinnamomeus |
63 |
0 |
4/m |
|
Nycticorax nycticorax |
105 |
0 |
6/m |
See Table I for common names of birds.
Table VI. Kruskal–Wallis all–pairwise comparisons test of observations by habitat
|
Name of activity |
Mean value |
Homogenous group |
|
Walking slowly |
112.13 |
A |
|
Stand and wait |
109.71 |
A |
|
Lean and wait |
93.542 |
A |
|
Stand and feed |
84.417 |
AB |
|
Perching |
71.250 |
ABC |
|
Prey chasing |
68.750 |
ABC |
|
Walking quickly |
60.792 |
ABC |
|
Wing flick |
40.625 |
BC |
|
Aggressive |
40.417 |
BC |
|
Gleaning |
26.083 |
C |
|
Toe shuffling |
23.792 |
C |
Alpha value, 0.05; Critical value, 3.317; Critical value for comparison, 51.799
often foraged in mixed flocks. While some Ardeids have been considered as solitary feeders, a few as group feeders and some as both solitary and group feeders (Kushlan and Hancock, 2005) it seems that most species may switch between solitary vs group-feeding, depending on the habitat and prey availability (e.g., Wiggins, 1991; Dimalexis et al., 1997; Kazantzidis and Goutner, 2008). We also found that the little egret and Eastern cattle egret were the most active foragers, which is supported by other studies (e.g. Aboushiba et al., 2013). Furthermore, these two species, together with the intermediate egret, were the most aggressive, which may be an indication of increased aggressiveness in group-feeding vs solitary foraging (e.g. Post, 2008).
Our results also indicate that ardeids are habitat specialists, similar to Choi et al. (2008). For example, the great egret, grey heron and purple heron preferred deep water devoid of vegetation, probably because they feed on larger–sized prey, often waiting patiently for their prey to come within the range of the beak and neck (Voisin, 2010). The little egret, intermediate egret, little heron, Chinese pond heron, Indian pond heron and Javan pond heron utilized the wetland edges and tended to congregate in shallow waters, especially in ditches, where water was shallower than the length of the tarsus, to catch fish fingerlings, aquatic invertebrates, i.e., backswimmers, mollusks, orthopteran larvae, and even amphibians. In contrast, the cinnamon bittern selected emergent vegetation to hide in and hunt for aquatic insects resting on the vegetation (e.g. Paszkowski and Tonn, 2000; Gawlik, 2002). The Eastern cattle egret was the only species that frequently used the agricultural fields and grassy areas for foraging. They often followed the cattle to feed on grasshoppers, crickets, mole crickets and beetles that hide in ground vegetation and disperse with the movement of animals (Kour et al., 2014).
These differences in habitat selection reflect differences in tarsus length and beak morphology (Voisin, 2010). Additionally, vegetation composition and structure, water depth, and prey size and richness also influence habitat selection in wading birds (Wiens, 1989; Bancroft et al., 2002; Gimenes and Anjos, 2006; Stolen, 2006). In general, the abundance and diversity of food resources influence the spatial and temporal fluctuation of bird populations (Butler and Vennesland, 2000; Gaines et al., 2000) and indicate the productivity and suitability of habitats (Gimenes and Anjos, 2006). Overall, differences in foraging techniques and habitat use within a guild are an indication of resource partitioning (Weller, 1999; Gatto et al., 2008; Lopez de Casenave et al., 2008) also observed among ardeids (e.g. Ye et al., 2021; Abbasi and Khan, 2023).
Lungh Lake is a small freshwater lake, in an ancient arm of the Indus River, fed by surplus water from the surrounding rice paddies. The wetland has almost disappeared because of overgrown vegetation and is listed among the most threatened wetlands of the area (Izhar–uI–Haq et al., 2016). We have shown that Lungh Lake is a highly productive and attractive habitat for Ardeid species. It is part of the wetland complex of the Central Indus Plain where a multitude of human activities, including harmful fishing methods, overfishing, extensive use of agro–chemicals, urban and industrial wastes, hunting and removal of flora are causing serious damage to the wetlands and associated biodiversity in this region (Khan and Arshad, 2014). The biodiversity of Pakistan’s wetlands reflects the passage of the Indus River, spanning from high mountains to the lowland areas that finally drains into the sea (Chaudhry, 2010). It has great potential to generate sustainable revenue, such as eco-tourism, which can provide earnings for the inhabitants who largely depend upon the wetland resources of the region (Khan and Arshad, 2014). Pakistan supports over 780,000 hectares of wetlands, covering 9.7% of the total land area, including 225 nationally significant sites, out of which 19 are Ramsar sites (Chaudhry, 2010). The wetlands of Pakistan are under tremendous stress due to unsustainable human practices (Khan and Arshad, 2014). A lack of awareness about their ecological services is a major threat to their conservation, and there is an urgent need for National and Regional Wetland Management Plans to be drafted (Chaudhry, 2010; Khan and Arshad, 2014; Izhar–uI–Haq et al., 2016). Therefore, we propose that the conservation of Lungh Lake habitat is essential for Ardeid protection. Our study confirms the niche partitioning hypothesis, in which Ardeids don’t overlap their foraging strategies to catch and consume their prey, meaning they often select heterogeneous locations and different water depths to do so.
CONCLUSION
Based on the findings, Ardeids employ a wide range of foraging techniques while capturing different food items and exploit different habitats where prey items often concentrate, particularly in shallow waters, lake edges, and thick matts of sedges.
Declarations
Acknowledgement
We would like to express our thanks to the Sindh Wildlife Department Larkana Division for supporting the collection of data.
Funding
The study received no external funding.
Ethical statement and IRB approval
Verbal approval was obtained from Wetland Sanctuary Warden in charge for data collec-tion. In this study, bird data were collected using the Distance Sampling Point Count Method. Da-ta on wild birds was collected in accordance with guidelines for wild bird research. The stress on birds was minimized at all costs. The Vanguard Platinum spotting scope (20 x 80mm) and binoculars (Olympus; 10 x 50mm) were used for direct observations, which did not cause stress to birds.
Generative AI and AI-assisted technology statement
The authors declare that no generative AI and AI assisted technology was used in the creation of this manuscript.
Statement of conflict of interest
The authors have declared no conflict of interest.
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