Effect of North Atlantic Oscillation and El Niño – Southern Oscillation on return rates, body mass and timing of migration of Common Terns breeding in Germany

FAVERO M & PH BECKER

Waterbirds of the World

The Stationery Office

Lugar: Edinburgh; Año: 2006; p. 405 - 409

Environmental variability at breeding and wintering areas may have complex effects on populations of migratory seabirds. Here, we report on the correlation of climate variability in the winter quarters and at migration stopover sites with return rates, individual condition and migration strategy of Common Terns Sterna hirundo breeding in northern Germany. Climate variability was defined by the North Atlantic Oscillation Index (NAOI) and Southern Oscillation Index (SOI, a measure of the El Niño-Southern Oscillation). Data on Common Terns were obtained over the last ten years at a breeding colony in the Banter See (northern Germany) by systematically marking adults and fledged chicks with transponders. The return rate of breeders was negatively correlated with the NAOI in the previous year, but for two-year-old sub-adults was positively correlated with the lagged SOI, indicating possible dependence for survival on food availability at migration stopover sites and in the wintering areas, respectively. Sub-adults also arrived later at the breeding colony after years of high NAO, suggesting that conditions at the wintering sites and during spring migration strongly influence the survival and behaviour of prospecting terns. The sub-adults appear to be more dependent on climatic conditions at wintering and migration stopover sites than adults, possibly as a result of different migratory behaviour, or foraging experience and the breeding requirements of adults. Studies on the wintering and migration strategies of the species are required to confirm the mechanisms linking migration and climate variability.Sterna hirundo breeding in northern Germany. Climate variability was defined by the North Atlantic Oscillation Index (NAOI) and Southern Oscillation Index (SOI, a measure of the El Niño-Southern Oscillation). Data on Common Terns were obtained over the last ten years at a breeding colony in the Banter See (northern Germany) by systematically marking adults and fledged chicks with transponders. The return rate of breeders was negatively correlated with the NAOI in the previous year, but for two-year-old sub-adults was positively correlated with the lagged SOI, indicating possible dependence for survival on food availability at migration stopover sites and in the wintering areas, respectively. Sub-adults also arrived later at the breeding colony after years of high NAO, suggesting that conditions at the wintering sites and during spring migration strongly influence the survival and behaviour of prospecting terns. The sub-adults appear to be more dependent on climatic conditions at wintering and migration stopover sites than adults, possibly as a result of different migratory behaviour, or foraging experience and the breeding requirements of adults. Studies on the wintering and migration strategies of the species are required to confirm the mechanisms linking migration and climate variability.