Mortality rates of puffin Fratercula arctica and guillemot Uria aalge and fish abundance in the North Sea

The populations of puffins and guillemots on the Isle of May, East Scotland increased greatly during the 1960s and 1970s. These increases ceased in the 1980s. Breeding success remained high but there were declines in the survival rates of adult, and possibly also immature, puffins and an increase in the number of ringed guillemots recovered in the first winter of life. These changes appeared to be linked with a change in the number and distribution of sprats