Environmental chemicals in eggs of Dunlins (Calidris alpina) from NorthernNorway compared to eggs of coastal bird species breeding in the Wadden Sea

Owing to the international importance of the Wadden Sea for waders and wate rfowl a long-term program to monitor chemical contamination of birds breedi ng in the Wadden Sea has been established in the early 1980s with Oystercat cher (Haematopus ostralegus) and Common Tern (Sterna hirundo) as monitor sp ecies. However, numbers of birds breeding in the area are only 10 % compare d to numbers of birds using it as a wintering, moulting or staging area, an d little is known about contamination of those non-breeding birds. In 1993 we compared contamination levels in eggs from eight species (Shelduck Tador na tadorna; Eider Somateria mollissima; Oystercatcher; Avocet Recurvirostra avosetta; Redshank Tringa tatanus; Black-headed Gull Larus ridibundus; Her ring Gull Larus argentatus; Common Tern) breeding at the island of Spiekero og (German Wadden Sea) with those from Dunlins (Calidris alpina alpina) bre eding in Northern Norway (Gamvik). It is known that many Dunlin from this a rea use the German Wadden Sea for staging. We analyzed contaminant levels o f 21 industrial chemicals (PCBs, HCB, Moschusxylol, Octachlorstyrol, Mercur y) and biocides (DDT and metabolites, HCH-Isomers, Bromocyclen). Common Ter n and Herring Gull eggs reached highest C-PCB levels whereas mercury had th e highest concentrations in eggs of Elder, Oystercatcher and Common Tern as well as C-DDT in eggs of Black-headed Gull. Bromocyclen could not be detec ted in eggs of the breeding species, whereas Moschusxylol was found in 29 % of the eggs and Octachlorostyrol in 57 %. Contaminant levels were in most cases above the levels given by German law for eggs used for human food but are probably not high enough to show an effect on the breeding success of the different species. In comparison to these results contaminant levels in eggs of Dunlins from Northern Norway were low and showed a similar chemica l pattern as for migrating waders breeding in the Wadden Sea detected. For the first time Bromocyclen residues could be detected in bird eggs.