FIGURE 4. Yearly variability in abundance (ind. per sample), as represented by GAM smooth functions for Sulidae (a) and Procellariidae (b). Climate oscillation event, due to the Indian Dipole mode, as represented by the Dipole Mode Index (DMI) value, during the month of sampling (c). DMI values represent the SST anomalies gradient between the western and eastern tropical Indian Ocean (Saji & Yamagata, 2003).