Mercury load according to moulting area in primaries of the nominate race of the Lesser Black-backed Gull Larus f. fuscus

Abstract

The effects of environmental loading on the levels ofmercury in primaries ofthe Lesser Black-backed Gull Larusf fuscus were studied in the Gulf ofFinland in 1979-91 . The mercury levels in the shed primaries found at the birds' breeding ground differed according to the site of feather growth . In the primaries grown at the breeding ground by the Baltic Sea, the levels of mercury tended to increase all through the 80s, correlating with the mercury levels in the Baltic herring (Clupea harengus). No temporal trends could be discerned in the "African" feathers . It is suggested that the mercury load derived from the species' staple food in the Baltic nowadays contributes more to the mercury level in moulted primaries than the load derived from food in the African wintering grounds.