Old Photos Used to Study The Fate of a Swedish Seabird Colony

Nearly 100 years of old tourist photos got a second life recently when researchers used them to reconstruct the rise and fall of a colony of seabirds on the Swedish island of Stora Karlsö. The island, designated a nature preserve in 1880 and a popular tourist destination since the 1920s, hosts a large population of common guillemots, one of the biggest species of auks. Ecologists Jonas Hentati-Sundberg and Olof Olsson of Stockholm University spent five years collecting images of the island from archives, museums, and island visitors in order to count guillemot numbers decade-to-decade. They found that the colony declined in the 1960s and 70s, when contaminants like DDT and PCB were prevalent, but has since rebounded to historically high numbers today, possibly because of an increase in the numbers of forage fish consumed by guillemots. “The population is currently increasing at an unprecedented rate of about 5 percent annually,” said Hentati-Sundberg. “This is interesting in that many common guillemot populations are decreasing worldwide.”