The Swedish island of Stora Karlsö in the Baltic Sea became a nature conserves with regulated hunting back in 1880 , and member of the Swedish bourgeoisie frequent the island in the early 1900s . By the 1920s , the secret company that possess the island began offering daily tour of duty . today , Stora Karlsö still obtain thousands of visitors a class , and that stand for its seabird colony have been photograph again and again for almost a hundred .
In the absence of long - terminus scientific records , researchers studying amateurish photograph have been capable to dog the rise and fall of the island ’s uncouth guillemot ( Uria aalge ) , a Pisces - eating seafowl that nest in breeding colonies . After suffering serious declines , their number are currently at a historic high , according to findings bring out inCurrent Biologythis workweek .
Stora Karlsö host two - third of the entire Baltic Sea population of common guillemot . These big , inglorious - and - blanched auks were hard eat in the former 1900s because of intense hunting and egg aggregation . But while those practices terminate , the birds then confront oil spills , chemicals , and tangles of fishing gear .
Jonas Hentati - Sundberg and Olof Olsson of Stockholm University collected 113 photographs spanning 37 geezerhood between 1918 and 2005 from home and regional archives , commercial stock pic agencies , and request to the public in magazines , internet assembly , and a local radio station . They complement their collection with a photograph documentation of the colony from 2006 to 2015 . Using these photo , the couple reckon the number of breeding birds each class based on 65 subareas .
As expected , pic from the early 20th one C showed the lowest numbers of fosterage guillemot . Then , the use of pesticide DDT and environmental contaminant PCB may have caused the pickpocket they keep in the mid-1960s and mid-1980s . Also during that prison term , Atlantic salmon fisheries using driftnets were expanding rapidly , and adult seabirds sometimes ended up as by-catch .
The population has been growing since the 1980s , thanks to a combination of hunting regulations , fewer oil release , decreasing environmental contaminants , and the decline ( and late prohibition ) of driftnet sportfishing . Now , while many usual guillemot population are decreasing worldwide , the population on Stora Karlsö is more than five fourth dimension bigger than it was in the early 1900s . They ’re currently increasing at an unprecedented pace of about 5 per centum a yr .
Image in the text : breed Common guillemots on the island of Stora Karlsö in 1960 . Gösta Håkansson / Gotland museum collection
