Dynamics of mercury in blood and feathers of greet skuas

Mercury dynamics in the blood and feathers of captive great skuas, Catharac ta skua, were monitored over 56 weeks. Prior to the onset of molt, mercury intake was solely from their maintenance ration of sprats, Sprattus sprattu s. For the first half of molt, in addition to mercury intake from sprats, b irds were fed different doses of methylmercuric chloride weekly for 20 week s. During the second half of molt, dosing was stopped and mercury intake wa s solely from sprats. Blood was sampled throughout the study and feather gr owth was monitored. Prior to the onset of molt, mercury concentrations incr eased over the first 51 to 71 d and appeared to level off after this period . Repeated dosing models based on mammalian pharmacokinetics were, in gener al, too simplistic to be applicable to the birds in the study. During molt, the elimination of mercury from the brood is probably best described by a three-compartment model. Mercury concentrations in feathers were significan tly correlated with those in Mood at the time of their growth, suggesting t hat blood and feathers reflect mercury intake over the same time period. In dividuals varied in their ability to excrete ingested mercury into the feat hers.