Copper is an essential element that is metabolically regulated in the tissue of seabirds. The levels of copper in muscles do not differ much and are generally low (from 15 to 25 mg/kg dry weight). Copper might be higher in liver (not shown in maps) of scavenger birds and in common- and king eiders. The eider mainly feeds on mussels, snails and crustaceans which have hemocyanin (contains copper) as their blood pigment. Therefore they may have relatively high levels of copper in the liver.No regional difference was found in copper levels.