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  • This dataset contains calculated return rates for five seabird species from representative colonies on the Isle of May, off the East coast of Scotland. Annual return rates are measured as the number of individually colour marked individuals seen in any one year that were also observed in the previous year for the Atlantic puffin (Fratercula arctica), common guillemot (Uria aalge), razorbill (Alca torda), European shag (Phalacrocorax aristotelis) and black-legged kittiwake (Rissa tridactyla). Not every individual is seen in any one year and the data set does not take into account those missed in any previous years hence these data are not to be treated as survival estimates. The Isle of May long-term study (IMLOTS) aims to identify the impact of environmental change on seabirds and their associated ecosystems. Understanding the mechanisms underlying variation in seabird population size requires a thorough knowledge of demographic parameters, namely birth rates, death rates, immigration and emigration. The effects of environmental change are likely to be different according to which demographic parameter or life history stage is being considered. This complexity means that only long-term monitoring, such as that carried out on the Isle of May, will allow us to understand the functioning of bird populations and their responses to environmental change. Full details about this dataset can be found at

  • This is a dataset generated from information extracted from previously published studies, for the purpose of a meta-analysis investigating fitness benefits of different migratory strategies in partially migratory populations. Each line of data includes a mean and associated variance for a given fitness metric for both migrants and residents extracted from a study, in addition to information concerning population location, study species, type of fitness metric, year data were collected, and details on the publication from which the data were obtained. Data were collected as part of a NERC-funded PhD project, grant number NE/L002582/1. Full details about this dataset can be found at