To leave or not to leave: survival trade-offs between different migratory strategies in the greater flamingo
1. The balance between costs and benefits of migration under different environmental, density-dependent and individual conditions may promote a broad range of migratory behaviours. We studied the factors influencing first-year migration and subsequent fidelity or dispersal among wintering areas, and the survival costs of different wintering behaviours in the greater flamingo (Phoenicopterus roseus). 2. We analysed by multievent capture-recapture modelling among-site dispersal/fidelity and site-dependent survival probabilities from 22 671 flamingos ringed in the Camargue (France) between 1977 and 2010 and resighted subsequently in their wintering grounds classified as France, Iberian Peninsula, Italy and North Africa. 3. We found that first- and second-year birds either resident or wintering at medium distances from their birth place, survived better than those wintering further afield. However, under severe winter conditions (extremely cold winter 1984-1985), individuals with the sedentary strategy suffered the highest levels of mortality. From the third winter onwards, the pattern of survival reversed: the long-distance wintering individuals (i.e. North Africa) survived better. 4. The proportion of first-year birds migrating for wintering was highly variable among cohorts and increased with favourable environmental conditions (wet years). After the first winter, birds showed high fidelity (>90%) to their previous wintering area and wintered preferably near their natal colony when they became adults (>2 years). 5. Survival estimates suggest that long-distance migration was costly for young and inexperienced individuals. Nonetheless, for adults, the most southern wintering areas seem to offer the most favourable local conditions for overwinter survival. 6. The higher availability of intermediate stopover sites during wet years may facilitate first-year migration. Then, once they have some wintering experience, flamingos appear to favour the known wintering grounds. As they grow older, dispersing towards the vicinity of the natal colony may provide higher breeding prospects for individuals wintering closer to this high-quality and saturated breeding ground, as predicted by the arrival-time hypothesis.