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Keywords:

  • SST;
  • time series;
  • ARIMA;
  • modelling;
  • small populations;
  • biological effects;
  • El Niño

Abstract

El Niño Southern Oscillation events have been associated with large fluctuations in seabird and landbird populations of the Galápagos Islands. We reveal different effects of climatic variation on the abundance and distribution of a waterbird, as illustrated by the flamingos Phoenicopterus ruber living in saline coastal lagoons of the arid Galápagos environment. Using time series analyses [autoregressive integrated moving average (ARIMA)] to model the temporal variations in abundance, we found significant correlations between rainfall, lagoon water level (LWL), lagoon temperature and flamingo abundance. Although these variables were good predictors of flamingo abundance, they explained <50% of the variance in monthly counts. During the strong El Niño event of 1982–1983, extreme rainfall resulted in an increase in LWLs (>300 mm above the long-term mean) and a record decline in flamingo numbers. Monthly abundance of flamingos was lower, on average, during the rainy season (between January and May) when LWLs were above their seasonal mean. Flamingo abundance at the two lagoons on Isabela Island and those at ‘all other lagoons’ in the Archipelago showed a significant negative correlation. We infer that moderate reductions in the abundance of flamingos in the rainy season and significant temporary declines during El Niño events are explained by movements between lagoons within the Archipelago rather than by mortality. This illustrates the general principle that climate change may, without directly affecting population sizes, prompt adaptive behavioural changes with the potential to affect population biology.