Geographic variation in reproduction and survival of kelp gulls Larus dominicanus vetula in southern Africa

摘要

Different populations of a species tend to vary in survival and reproduction, but the extent and scale of suchspatial variation are poorly known. We estimated survival and clutch size of kelp gulls Larus dominicanus vetulaacross their entire African range. At this large geographic scale, we found no evidence for spatial variation insurvival, and there was no variation in clutch size. However, there was considerable variation in clutch sizeamong colonies within regions. Over the whole study, mean annual survival of juvenile and adult birds was 0.44and 0.84, and mean clutch size was 2.2 eggs. A matrix population model showed that population growth wasleast sensitive to variation in clutch size, and the observed variation in clutch size could not fully account for theobserved variation in population growth among colonies and regions. Our results thus suggest that dispersaland/or variation in survival (including eggestling survival) at a small spatial scale are also important for thespatial pattern of kelp gull population dynamics. These results are consistent with a metapopulation approach tospatial population dynamics.