Survival synchronicity in two avian insectivore communities

Climate change is forecast to increase climatic variability, in particular the occurrence of extreme events. Consequently, it is imperative to understand how climatic variation influences the dynamics of communities. We investigated synchronicity in survival in response to climatic variation among bird communities occupying habitats that differed in climatic seasonality: a more seasonal wetland and a less seasonal fynbos shrubland in South Africa. We predicted higher synchronicity at the wetland than at the shrubland because there was more potential for weather to induce variation in survival at this climatically more variable site. We estimated survival from ringing data for four wetland species and three fynbos species in hierarchical models with an asynchronous (species-specific) variance component and a synchronous (common) variance component. Comparing models including and excluding a climatic covariate enabled us to estimate the effect of climatic variation as a synchronizing and desynchronizing agent on survival. As hypothesized, synchronicity in survival was substantially greater at the more seasonal wetland than at the climatically more stable fynbos site: 0.50 (95% credible interval 0.01–1.92 on the logit scale) and 0.03 (0.00001–0.19), respectively. Similarly, asynchronicity in survival was greater for wetland species than for fynbos species. However, we found no clear evidence that weather affected survival. We provide the first survival estimates of several African endemic birds and the first estimates of synchronicity and asynchronicity in survival of communities outside the strongly seasonal northern temperate zone. Our results suggest that the relative magnitude of synchronicity and asynchronicity varies among communities and support the idea that environmental variability induces synchronicity.