This study evaluates the biodiversity of mangrove flora and associated macrofauna alongside physicochemical parameters of estuarine water and sediment, across four distinct sites in Goa (Verem, Nerul, Britona, and Divar). The objectives were to assess spatial variations in water and sediment quality, characterise the diversity of mangroveassociated communities using biodiversity indices, vegetation analysis, and correlate environmental parameters with biological diversity to elucidate the impact of anthropogenic pressure on mangrove ecosystems. Standardized sampling and laboratory protocols were employed for species identification and physicochemical analyses, including pH, temperature, salinity, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrates, and phosphates. Results revealed approximately 11 mangrove species across study sites. Physicochemical parameters exhibited site-specific variation: pH ranged from 6.75 to 7.52, salinity from 22 to 35 ppt, and temperature from 26 °C to 31°C. DO concentrations (5.22–7.97 mg/L) and BOD values (1.64–4.2 mg/L) indicated varying organic matter content, while COD values (0.16–0.84 mg/L) suggested differing degrees of pollution. Nutrient analysis showed phosphate concentrations between 0.01 and 0.25 mg/L in water and 0.11 to 0.34 mg/L in sediments, with nitrates ranging from 1.39 to 4.62 ppm in water and 0.24 to 12.36 ppm in sediments. Higher biodiversity indices, including Shannon-Wiener and Margalef, were associated with sites exhibiting lower organic and chemical pollution, signifying healthier ecological conditions. Conversely, sites with elevated nutrient and organic pollutant levels corresponded with diminished biodiversity, reflecting anthropogenic impacts. The study underscores the critical link between estuarine water quality and mangrove biodiversity, and highlights the urgency to implement conservation strategies to mitigate human-induced pressures on these vulnerable ecosystems in Goa.
Creating a species checklist for a given area or ecosystem is a prerequisite for ecological studies, biodiversity assessments, conservation reports, and other analyses related to animal diversity. Nijhum Dweep National Park in Bangladesh is an East Asian–Australasian Flyway Network Site for migratory waterbirds and an Important Bird and Biodiversity Area in the Ganges–Brahmaputra–Meghna delta. Despite its global importance for bird conservation, a systematic avifaunal checklist of the park was previously unavailable. Here, we present a comprehensive checklist based on surveys conducted from 2015 to 2020. We spent 86 days counting high-tide roosts in the mudflats and brackish marshes for waterbirds, and 40 days conducting strip-transect surveys in mangroves for inland bird species. We documented 161 bird species, including 20 new records for the park. Our checklist represents approximately 23% of all bird species recorded in Bangladesh. Of these, 50 species were passerines and 111 were non-passerines. Resident species comprised the majority (52%), with migratory species accounting for 48%. Notably, sixteen species on the list are of international conservation concern. The park is one of the last strongholds for non-breeding Indian Skimmers Rynchops albicollis, an Endangered species, and is also an important non-breeding site for the Critically Endangered Spoon-billed Sandpiper Calidris pygmaea and the Endangered Nordmann’s Greenshank Tringa guttifer. Our findings reaffirm the park’s significance as an Important Bird and Biodiversity Area and provide valuable baseline information for monitoring and conserving avian diversity in this protected area.
Songs of Phylloscopus c. castaniceps were examined at different elevations to understand how vocal behaviour and environmental factors shape song structure and diversity. Acoustic data were collected from multiple locations across Southeast Asia over a range of altitudinal bands between 2021 and 2023. Annotated song recordings (n=134) were used to extract metrics and analyze the Song Richness Index (SRI) and maximum frequency (Fmax) for each song. These metrics were analyzed using the Kruskal–Wallis nonparametric test, followed by post hoc pairwise comparisons using Dunn’s test. The findings revealed greater verse variation but lower song richness at lower elevations, likely due to competition for acoustic niches. Higher elevations, by contrast, showed higher song richness but fewer within-verse variations, indicating that minimal verses may be favoured in settings with fewer competitors. This pattern suggests that environmental factors exert strong influence on auditory cues. Additionally, the results showed significant variation in Fmax across different elevational bands (χ2(2) = 196.87, P = 1.78 × 10-43), suggesting that elevation-related environmental conditions affect song characteristics and transmission. Elevation and song richness were also positively correlated (χ2(3) = 77.84, P = 8.91 × 10-17), supporting the hypothesis that bird songs become more complex and diverse at higher elevations. Overall, these results demonstrate how environmental conditions shape song diversity in P.c. castaniceps, validating the acoustic niche hypothesis and highlighting the importance of incorporating altitudinal gradients into avian bioacoustics research.
