Diversity, Abundance and Interspecific Correlation in Water-Birds at Anasagar Lake, Ajmer

Anasagar Lake, situated in the north west of the Ajmer city is an important habitat for many resident and migratory birds. Various anthropogenic activities in most of its catchment area, have turned the lake into severely polluted water body. The perceived beautification of the lake has further added to the decline of avifaunal diversity around the lake. Water-birds play a very significant role in ecosystems. During this study seasonal variation in the diversity and abundance of water-birds and the correlation between their occurrence and numbers of individuals were determined. Transact walk, point transact and direct observation methods were deployed for water birds? survey from April 2016 to March 2017. During the total 92 visits made at the study site, forty species of water-birds belonging to 16 families and 9 orders were recorded. Diversity variables selected for the study were Shannon-Weiner diversity index, species richness, Shannon's equitability/evenness, effective number of species, mean frequency of occurrence and mean abundance of water-bird species. For relationship between occurrence and between numbers of individuals of different species, Karl Pearson's coefficient of correlation and coefficient of determination i. e. R-squared was used. Seasonal Variation in the various diversity variables at Anasagar Lake shows that during winter season species richness and mean abundance of species were highest but values of Shannon Weiner diversity index, Shannon's equitability and effective number of species for winter season were the least. Exactly opposite happened during autumn. This suggests indirect relationship in these variables. Mean frequency of occurrence of species was highest during monsoon and lowest in summer. This indicates that during monsoons water-birds frequently come out in search of new foraging opportunities for their old foraging and resting platforms are submerged. Correlation analysis between numbers of individuals of water-bird species revealed that there were significant positive correlations among 9 pairs of water-bird species including birds like Black headed gull, Little grebe, Great white pelican, Great cormorant, Indian cormorant, Little cormorant, Eurasian coot, Eurasian spoonbill and Lesser flamingo. Highest correlation was observed between Cormorant species and between Black headed gull and Great white pelican. These observations can be attributed to the fact that these species prefer similar habitat variables. Significant correlations were found between occurrences of four pairs of water-bird species i. e. between Common teal, Black headed gull, Great white pelican and Pied kingfisher. The results with the taxonomic families corroborated with the correlations in individual species. Order wise correlation analysis brought out that orders Suliformes and Pelicaniformes are correlated in terms of numbers of individuals throughout the year. Presence of one species indicates the potential of habitat for other correlated species, which can be explored further. For conserving the avifaunal diversity at the scenic Anasagar Lake, it is also necessary to monitor the water quality and encourage the growth of favourable emergent vegetation around the lake. For this study, CSIR New Delhi must be thanked for their indispensable support in the form of Senior Research Fellowship.