Waterbird species composition and its relative abundance
In total, 73 wintering waterbird species representing 11 orders and 19 families were detected from six potential wetland habitats between 2017 and 2022 (Table1, Figure 2 and Appendx 2). In addition, waterbird orders were categorized according to the families to understand which order possessed higher waterbird families. Based on the results, Charadriiformes was the dominant order containing the 5 families (26.31%), followed by Pelecaniformes (3 families, 15.78%), Suliformes, and Gruiformes (2 families, 10.52%). As opposed, there was only one family (26.67%) for each order: Accipitriformes, Anseriformes, Coraciiformes, Ciconiiformes, Passeriformes, Phoenicopteriformes, and Podicipediformes. In addition, the waterbird orders were classified based on the species composition. As far as waterbird species are concerned, the Charadriiformes (21.19%) held the highest number (20 species), followed by the Pelecaniformes (11 species; 15.06%), Suliformes (8.5%), Passeriformes (4 species; 5.47%), Coraciiformes (Coraciiformes, Gruiformes, Podicipediformes (3 species; 4.10 %) and Coraciformes, Phoenicopteriformes (2 species; 2.73%). However, Accipitriformes attracted only one waterbird species (1 species; 1.36%).
According to the observations recorded, the most prevalent waterbird species were gadwall – Mareca strepera(5.969%), little cormorant – Microcarbo niger (5.747), Great cormorant – Phalacrocorax carbo (5.531%), Great egret – Ardea alba(4.473%), northern pintail – Anas acuta(4.348%), and Eurasian wigeon – Mareca penelope(4.148%). Contrarily, Common crane – Grus grus (0.029%), Watercock – Gallicrex cinerea (0.028%), Common kingfisher – Alcedo atthis (0.019%), Large sand plover – Charadrius leschenaultii (0.015%), Little crake – Porzana parva (0.013%) and Yellow–wattled lapwing – Vanellus malabaricus (0.007%) were the rarest waterbird species detected with few individuals (Appendix 1). The relative abundance of waterbird in six wetland habitats was compared using Kruskal–Wallis One–Way Nonparametric and All–Pairwise ANOVA. The results shows that waterbird relative abundance in six wetland habitats located at heterogeneous localities were significantly different (F5, 437 = 8.14, p< 0.000).
The geographical distribution of wintering bird species in the study areas was categorized into Palearctic realm, Oriental realm, and Cosmopolitan species. In our study, Palearctic realm species (27.4%) are the most widespread followed by Cosmopolitan species (56.2%) and Oriental realm species is the less (16.4%; Figure 3).
Furthermore, based on the findings, the waterbird species were categorized as migrant, resident and vagrant. The finding stated that migrant waterbirds (61.60%) and native waterbird species dominantly utilized the wetland areas (38.40%). However, vagrant birds rarely preferred to exploit the wetland areas (0.036%; Figure 4).
Conservation Status
Out of 73 waterbird species, 10 species were identified as nearly threatened (NT = 9.812%), 2 species as endangered (EN = 0.229%), 3 species as vulnerable (VA = 5.682%), and 58 species as least concern (LC = 84.277% (Figure 5a). Dendrogram hierarchical cluster analysis revealed that waterbird species belong to four clusters among six wetland habitats. The branch lengths and topological changes on a dendrogram graph demonstrated the waterbird heterogeneity of IUCN conservation status in six wetland habitats (Figure 5b).
Foraging Guilds
Seven foraging guilds of waterbirds were detected based on the consumption of similar food items and foraging techniques. The Insectivore/Piscivore/Carnivore (47.548%) and omnivores (34.836%) was the most dominant foraging guild in study areas. Contrarily, Carnivore (0.326%) and Piscivore (0.319%) were the rarest foraging guilds (Figure 6a).
Dendrogram hierarchical clustering chart demonstrated that waterbird foraging guilds belong to four clusters. The branch lengths and topological changes on a dendrogram graph reflected the heterogeneity that waterbird foraging guilds among six wetland habitats (Figure 6b).
Waterbird Abundance and Diversity Indices
This study demonstrated that cattle egret – Bubulcus ibis, common sandpiper – Tadorna tadorna, Great cormorant – P. carbo, intermediate egret – A. intermedia, Eurasian wigeon – A. hypoleucos, ferruginous duck – Aythya nyroca, gadwall – M. strepera, little grebe – Tachybaptus ruficollis, northern shoveler – Spatula clypeata, and northern pintail – Anas acuta were all detected at six potential sites. However, Uchali and Raja wetlands harbored lesser flamingos – Phoeniconaias minor, Greater flamingos – Phoenicopterus roseus, and Pallas fish eagles – Haliaeetus leucoryphus. As per the findings, gadwall – M. strepera was the most abundant waterbird species, followed by little cormorant – Microcarbo niger, great cormorant – P. carbo, great egret – A. alba, and northern pintail – A. acuta, while white–tailed lapwing – V. leucurus was the least abundant detectable species (Figure 7).
The outcomes of the population parameters, i.e., species diversity, species richness, relative abundance, population trend, and species dispersion varied among six wetland habitats. Overall, the waterbirds have species diversity (Shannon’s Index;H' = 3.710 ± 0.097), species richness (Margalef’s Index;R = 5.88 ± 0.530), population trend (λ = 0.031), and species evenness (Pielou’s J index;E = 0.865 ± 0.023) in all six potential wetland habitats. Waterbird species richness (R = 4.724) was highest in the Chashma wetland, with relative abundance (RA = 26.612%), and species diversity (H' = 3.740) in Taunsa wetland. As well, the highest increase in population was determined in the Uchali wetland and the species dispersion in the Raja wetland. Contrary to this, the lowest species richness (R = 2.893) and species distribution (E = 0.766) was recorded in Uchali wetland, species relative abundance (RA = 4.184%) in Raja wetland, species diversity (H' = 3.288), population trend (λ = 0.027) in Taunsa wetland (Table 2 and Figure 8).
It is noteworthy that the hierarchical analysis found that many species of waterbirds were widely dispersed in habitats used for habitation and had habitat links at the appropriate geographical scales. Many waterbird species demonstrated significant seasonal and temporal variation in their occurrence and habitat usage. Time and space may cause changes in the parameters of a waterbird population (Figure 9).
Estimating the population size and distribution of waterbird species at appropriate spatial and temporal scales is crucial. Identifying geographical and temporal variations in waterbird populations among heterogeneous habitats was crucial to understanding the distribution, population dynamics, and habitat preferences of waterbirds. The results indicated a substantial correlation between the occurrence of waterbird species composition and suitable sites (Figure 10).
Temporal Pattern of Migratory Waterbirds
Interestingly, the parameters of the waterbird population varied yearly. It was evident from this study that the numbers of migrant waterbird species fluctuate from year to year depending on the location of the wetland habitat along the migration route (Table 3).
A Kruskal–Wallis one–way nonparametric and All–pairwise ANOVA analysis shows significant differences in waterbird detection in six wetland habitats at heterogeneous localities over five subsequent migration seasons (F5, 29 = 98.10, p < 0.000). Waterbird species diversity (F5, 29 = 176.00, p < 0.000) and population trend (F5, 29 = 126.00, p < 0.000) varied significantly as well. Further, waterbird species dispersion among six wetland habitats varied significantly over five subsequent migratory seasons (F5, 29 = 18.20, p < 0.000). This clearly indicated that waterbird species richness, species diversity, population trend, and dispersion varied spatially among six potential wetlands, namely Chashma, Dhap Chapak, Taunsa, Uchali, Haleji, and Raja wetlands over five subsequent migratory seasons. Based on statisitical results, we reject our null hypothesis (Table 4).