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Marine Ecology Progress Series

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MEPS 151:237-244 (1997)  -  doi:10.3354/meps151237

Influence of species, age and diet on mercury concentrations in Shetland seabirds

Stewart FM, Phillips RA, Catry P, Furness RW

Chick down, chick feathers and feathers from adults of 5 seabird species (Arctic skua Stercorarius parasiticus, great skua Catharacta skua, Arctic tern Sterna paradisaea, kittiwake Rissa tridactyla, and common guillemot Uria aalge) were analysed for mercury. Individual female Arctic and great skuas' body feather mercury concentrations correlated with concentrations in their chicks' down, but not feathers (Arctic skua: r = 0.64; great skua: r = 0.66). This demonstrated that mercury in chick down originated from the egg, and that mercury in the egg and in adult females' plumage could have the same dietary source. Inter-specific differences in mercury concentrations were found for all age classes sampled, and these could be explained partly in terms of dietary specialisation, although physiological variations may also be important. All 3 age classes of great skua showed a direct increase in mercury with increasing proportion of bird meat in the diet of individual pairs. In kittiwake, Arctic skua and great skua, adults had higher mercury concentrations than chicks and chick down had higher concentrations than chick feathers. However, in 2 species (Arctic terns and guillemots) chick down had higher concentrations than adult feathers. Chick down could be sampled for mercury content as an alternative to using eggs in national biomonitoring schemes. Feathered chicks could be sampled to determine mercury availability around the breeding colony between hatching and fledging.

Biomonitoring · Diet · Heavy metals · Individual variation · Mercury · Seabirds

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