Figure 4.

Potential factors influencing the evolutionary strategies and population persistence of sooty terns on Ascension Island and their interactions. A highly variable natural environment often leads to increased competition for space and food. Possible adaptive strategies to enable increased genetic plasticity and thus population persistence may include low levels of fine-scale spatial and temporal structure, coupled with dispersal within- and between-populations. Human activities increase the severity of environmental stressors (e.g. through anthropogenic climate change, overfishing and introduced predators) and limit population persistence through direct impacts on breeding success and survival (such as via egg harvesting).