Do El Niño events beget generations of reproductively deficient adults?

1. Warm ocean waters during El Niño events deplete primary productivity, with cascading effects through the food chain that profoundly affect many marine and terrestrial species, commonly increasing adult mortality and offspring starvation. With global warming, events will double and increasingly threaten the depletion or extinction of some animal populations. 2. Because adverse environments experienced during infancy generally induce reproductive deficits in adulthood, El Niño events are also expected to affect animals born during them, engendering generations of adults with reduced reproductive potential and exacerbating demographic impacts. 3. We made the first test of this idea, using the blue-footed booby, a piscivorous apex predator of the eastern tropical Pacific Ocean. Surprisingly, detailed monitoring of 18 generations over a 27-year period detected no deficits in the annual breeding success, offspring viability, lifespan or lifetime reproductive success of generations of adults born during El Niño years. 4. These results testify to remarkable developmental resilience extending across the lifespan. However, there was evidence that this resilience was supported by two mechanisms of quality control of adult generations from El Niño years. 5. First, viability selection on nestlings and fledglings was more severe for El Niño birth cohorts than ordinary cohorts. 6. Second, in El Niño years, adult boobies self-selected for breeding. There was no increase in the proportional representation of either high quality breeders or breeders in their peak years (middle-age), but there was an increase in old-young adult pairings, which in this population produce the most viable fledglings. 7. The blue-footed booby appears to be immune to the expected developmental impact of El Niño on the reproductive value of adult generations. The susceptibilities and resilience of other species need to be explored, to better predict the demographic impacts of this accelerating climatic oscillation.