The Isle of May long-term study (IMLOTS) seabird annual return rate 1988-2021

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. In the dataset, each year is represented by a single row of data, there are five columns showing the calculated return rates for each species (indicated by its common name and suffixed 'RR'). The figure quoted in any row is the proportion of marked birds which are observed by the end of the stated breeding season. Each row also contains the number of individuals seen in that year and the number seen in the previous year, taking into account new individuals which are marked.