Once the moult patterns have been taken into account, feather methylmercury levels can be used to accurately measure the mercury burdens of seabirds. We used body feathers from live seabirds and from museum collections to examine geographical and temporal patterns of mercury contamination in the North Sea. This approach identifies an increase in mercury concentrations in seabirds of the German North Sea coast during the last 100 years, especially high levels during the 1940s, and reduced contamination in the last few years. Comparisons among populations suggest that some increases in mercury levels are predominantly due to local pollution inputs, as on the German coast, while in other areas deposition from jet stream circulation of global contamination may be the major contributor. Mercury levels are far higher in seabirds from the German North Sea coast than in populations from the north and west North Sea or from most areas of the North Atlantic. We advocate the use of museum collections of birds for studies of long-term changes in levels of mercury contamination.

Seven eggs from four clutches of grey plovers (Pluvialis squatarola) breeding in the Lena Delta, Sakha Republic, Yakutia, in 1997 were analysed for persistent organochlorines and mercury. Contamination levels were low and within the same range as found in eggs from waders (Charadriiformes) breeding in north‐west Europe. One exception was ?HCH, averaging 99.2 ng g−1 fresh egg mass, a level about ten times higher than in wader eggs from north‐west Europe. β‐HCH accounted for 98% of the total HCH concentration. There are indications that the pesticide levels may reflect former local use. ∑PCB level (57.0 ng g−1, 62 congeners) and mercury concentration (68.7 ng g−1) can be considered low.

Organochlorine and mercury concentrations in eggs of grey plovers (Pluviulis squuturola) breeding in the Lena Delta, Seven eggs from four clutches of grey plovers (PI~wialis syuararola) breeding in the Lena Delta, Sakha Republic, Yakutia, in 1997 were analysed for persistent organochlorines and mercury. Contamination levels were low and within the same range as found in eggs from waders (Charadriiformes) breeding in northwest Europe. One exception was CHCH, averaging 99.2 ng g-' fresh egg mass, a level about ten times higher than in wader eggs from northwest Europe. P-HCH accounted for 98% of the total HCH concentration. There are indications that the pesticide levels may reflect former local use. CPCB level (57.0 ng g-', 62 congeners) and mercury concentration (68.7 ng g-') can be considered low.