Persistent organochlorine levels in six prey species of the gyrfalcon Falco rusticolus in Iceland

Our previous investigations have revealed very high levels of organochlorin es (OCs) in the Icelandic gyrfalcon Falco rusticolus, a resident top predat or. We now examine six potential prey species of birds, both resident and m igratory, in order to elucidate the most likely route of the OCs to the gyr falcon. The ptarmigan Lagopus mutus, the most important prey of the gyrfalc on, contained very low levels of OCs. Bioaccumulation of polychlorinated bi phenyls (PCBs) and DDTs in mallards Anas platyrhynchos, tufted ducks Aythya fuligula, golden plovers Pluvialis apricaria, purple sandpipers Calidris m aritima, and black guillemots Cepphus grylle reflected their position in th e foodchain. The differences in OC-levels seem nevertheless too high just t o reflect the different foodchain levels of these species in Iceland. The w inter grounds of the migratory golden plovers and tufted ducks appear to be more contaminated than the Icelandic terrestrial habitat of ptarmigans or the freshwater habitat as reflected in mallards, both resident species. How ever, spending the winter on the coast in Iceland, results in high levels o f contaminants in purple sandpipers and black guillemots. Our results indic ate OC contamination of the marine ecosystem in Iceland while the terrestri al and freshwater ecosystems are little affected. It is postulated that gyr falcons receive the major part of the observed contamination from prey othe r than ptarmigan, especially birds associated with the marine ecosystem and also from migratory birds, (C) 2001 Elsevier Science Ltd. All rights reser ved.