The collapse of environmental predictability erodes reproductive success in a Tropical seabird

Climate change can alter not only when seasonal events occur on average, but also how predictable they are from year to year. Many long-lived seabirds show a paradox: breeding dates remain stable even as populations decline. Using two decades of data from Blue-footed Boobies (Sula nebouxii), we tested whether loss of environmental predictability could reduce reproductive success even when mean timing remained stable. Mean timing of the winter–spring phytoplankton bloom and mean breeding mismatch showed no clear trend, but year-to-year variability in bloom timing increased markedly. Mismatch relative to bloom onset became more variable, and both expected nest success and its consistency declined. These results show that predictability loss can erode synchrony and demography even when mean timing appears unchanged