Modes of climate variability and associated bird communities in India

Birds are sensitive to climate variability and change. This pilot study explores variations in bird communities in India under contrasting phases of the El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Statistical analyses were performed using monthly bird data for the years 1990-2015 in Goa and Tamil Nadu. Monthly precipitation, temperature, the Oceanic Nino Index and the Dipole Mode Index were used as explanatory variables for species richness and counts of three marker species (Brahminy Kite, Indian Pond Heron and Lesser Whistling Duck). Due to highly autocorrelated series, small sample sizes and many test permutations, there is greater likelihood of Type I errors when interpreting correlation results. However, pooling bird data by climate mode and state revealed that species richness was generally greater under El Nino or negative IOD (locally wet conditions) than under La Nina or positive IOD (locally dry conditions). In Goa, the Brahminy Kite, Indian Pond Heron and Lesser Whistling Duck had significantly higher counts during El Nino than La Nina events. In Tamil Nadu, there were significantly more Kites under negative than positive IOD phases. Regional variations in sensitivity may reflect species-dependent factors such as food availability and security of nesting sites. Further research is needed to establish causal mechanisms between climate mode and species richness as well as into the combined effects of ENSO and IOD on bird communities across South Asia.