This dataset contains calculated breeding success rates for six seabird species from representative colonies on the Isle of May, off the East coast of Scotland. Annual breeding success has been measured as the number of chicks fledged per active nest for the Atlantic puffin (Fratercula arctica, since 1982), common guillemot (Uria aalge, since 1982), razorbill (Alca torda, since 1982), European shag (Phalacrocorax aristotelis, since 1987), black-legged kittiwake (Rissa tridactyla, since 1987) and northern fulmar (Fulmarus glacialis, since 1987). The number of active nests recorded are also provided. Data were collected as part of the Isle of May long-term study (IMLOTS), which aims to identify the impact of environmental change on seabirds and their associated ecosystems. This monitoring has been ongoing since 1974, by essentially the same team of scientists, using the same well-documented methods throughout this time.