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Résumé :
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Concentrations of total mercury were determined in the livers of seventy-three waders (Limicolae) collected during August–March on the Wash, eastern England, in order to obtain baseline data on levels of this element in birds living in a non-industrial and presumably lightly polluted estuarine area. In the knot (Calidris canutus), mercury levels were relatively low, about 1 ppm dry weight, in early autumn but increased through the winter until, by February–March, they were about 10–20 times higher. On more limited or scattered data, the dunlin (C. alpina) and redshank (Tringa totanus) also showed much higher mercury levels in late winter compared with autumn. The results imply that mercury accumulated in the liver during the winter months (when the birds are exclusively estuarine, mainly in temperate latitudes) is eliminated in summer (on mainly inland arctic and subarctic breeding grounds). The results are discussed in relation to the moult, movements and food of the main species. The biological significance of the concentrations found in the Wash waders is uncertain, but it is suggested that in industrial estuaries mercury levels in the same species may be very much higher and, by analogy with other species, could be having detrimental physiological effects.
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