Movements, morphology, breeding, molt, diet and feeding of seabirds in the Azores

This paper describes the structure and ecology of the Azores seabird assemblage. Recent observations on movements, morphology, breeding, molt, diet and feeding are combined with a literature review to provide a comprehensive framework for future research. The local populations of small Procellariiformes show a slight tendency to be larger body-sized, compared to southern Macaronesian allopatric populations, but this is not true for the large Cory's Shearwater. Among the Laridae, the Common Tern is slightly but consistently larger than among other eastern and western North Atlantic populations. The Azores seabirds exhibit fixed predictable annual breeding cycles and the phenology of Procellariiformes shows an overall similarity with those at Madeira, Salvages and Canary Is. The chick rearing periods of Procellariiformes with similar ecological niches do not overlap, suggesting partitioning of breeding habitat and food resources. The most important colonies are multispecific. Inter-specific competition for nest sites is high among Procellariiformes and this presumably reflects negatively on their breeding success. Intra-specific competition for nest sites is important among Cory's Shearwater and it is the possible reason for the evolution of temporally segregated populations of Band-rumped Storm-Petrel. Adults of species with high nest-site tenacity show poor body condition int the pre-laying period, which reflects the high cost of nest site maintenance and defense. Most species feed opportunistically on a wide variety of shoaling fish and squid. They produce their young in late spring and summer which apparently coincides with the period of maximum food availability. The petrels exploit vertically migrating mesopelagic fish and Cory's Shearwater feeds often in association with marine predators such as dolphins and tuna. Seamounts with associated upwellings are important foraging areas for seabirds.