Mercury levels in feathers of eagle-owls Bubo bubo in a captive, a reintroduced and a native wild population in SW Sweden

Mercury levels in feathers are presented for both captive and wild eagle-owls from the period 1963-1976. Levels are compared between wild birds occupying old territories and released birds in newly occupied territories. The wild population in SW Sweden shows decreasing levels in the inland territories, and at present these levels are similar to the natural background level. The coastal owls have significantly higher levels which show no decrease. Low levels prevail in captive eagle-owls, fed on low-contaminated food. Birds in newly occupied territories (mainly released birds) have similar mercury levels as native birds. After being released captive birds therefore seem to accumulate mercury rather quickly.