Welcome to the American Ornithological Society 2018 Annual Conference. We are pleased to have you join us at the lovely Hilton El Conquistador Resort in Tucson, AZ.
Tropical oceans have limited food resources when compared to polar or temperate oceans, which impact the foraging habits of tropical seabirds. Understanding foraging strategies through 15N and 13C stable isotope analysis, representing trophic status and foraging location respectively, is a valuable technique for investigating dietary shifts in seabirds. Mercury (Hg) analysis can be performed in conjunction with stable isotope analysis for a more thorough understanding on contaminant exposure with foraging behavior. Because the Galápagos Islands seabird community is directly impacted by El Niño Southern Oscillation (ENSO) cycles, understanding their foraging behavior in response to these events is important for future conservation plans. However, little research has been done with Galápagos seabirds at the community level. We sought to address whether there is a shift in stable isotope and Hg values, and thus diet, in species before, during, and after the 2015 ENSO event. Breast feathers from six nesting seabird species (Sula sula, S. granti, S. nebouxii, Fregata minor, Cregarus furcatus, Phaethon aethereus) were sampled across five years (2011, 2014-2017) and analyzed for 15N and 13C isotopes and total Hg (ppm). These sampling periods occurred at different points in the ENSO cycle, allowing shifts in foraging behavior to be monitored as environmental conditions change. Preliminary results show higher Hg contamination associated with La Niña. Additionally, as prey abundances decrease with the onset of El Niño in 2015, most species show more negative 13C values, representing more pelagic foraging grounds. This information can help inform management plans during the different ENSO phases.
