Effects of El Niño and La Niña Southern Oscillation events on the adrenocortical responses to stress in birds of the Galapagos Islands

John C. Wingfield, Michaela Hau, P. Dee Boersma, L. Michael Romero, Nigella Hillgarth, Marilyn Ramenofsky, Peter Wrege, Robert Scheibling, J. Patrick Kelley, Brian Walker, Martin Wikelski