Complete description of the study that the photographs are part of is available in the following scientific publication:
Olsson, O. & Hentati-Sundberg, J. 2017. Trends and status of four seabird species at Stora Karlsö in the Baltic Sea. Ornis Svecica (2)
Purpose:
The purpose is that this documentation of photographs shall be available for future censuses of the common guillemots at Stora Karlsö