Many seabird species are nocturnal and breed in deep burrows to avoid predation. Because these species are not easily visible in their breeding colonies, they cannot be counted visually, and population trends are unknown for most populations. However, most of these species are very vocal, and the volume of vocalisations is approximately proportional to the size of a colony. Since 2009 we have therefore deployed sound recorders on various islands to investigate the abundance and population trend of various seabird species. The objective of these recordings was to overcome the short-term variability (due to weather, moon phase, breeding stage etc.) in call intensity by deploying automated acoustic recorders for many months on breeding seabird islands, and record sound every night according to some pre-defined schedule. The recordings will mostly contain the calls of the respective target species (Cory’s Shearwater, Manx Shearwater, Yelkouan Shearwater, St Helena Storm Petrel), but will also contain calls of other species and background noise.