Breeding biology and population dynamics of a colonial seabird: The Razorbill Alca torda. A long-term study of an expanding Razorbill colony on Græsholmen in the central Baltic Sea, 1983-2011.

With a 29-year long data series, exceeding the average life expectancy of a Razorbill, this study gives a detailed picture of the life and dynamics of a seabird colony in the central Baltic. The Razorbills on Græsholmen were generally living under very good conditions during the study years (1983-2011). Annual survival rates for adult breeding birds (93-95%) and for young birds to the age of first breeding (4Y, 57.7%) were among the highest recorded in any study. Mean annual breeding success (73%) was also high. The rate of annual adult nonbreeding was low (3%). The high number of 1-2Y birds visiting Græsholmen and the relatively high numbers of birds starting to breed when 3 years old also suggest good conditions for the breeding population.