The relationships between mercury levels in eggs, tissues, and feathers of male and female herring gulls caught at their nests at a colony on the German Wadden Sea Coast were investigated, and an assessment of mercury intake and excretion of these birds was made. Samples of the liver, ovary, pectoral muscle, and body feathers, as well as the primary feather (in some cases), and eggs were taken from 37 adult herring gulls. Analysis of total mercury in all samples showed that body-feather and tissue levels were independent of sex. There was, however, a significant difference between levels of mercury in the primary feathers of male and female birds. Egg levels were not correlated to pectoral muscle, ovary, or feather levels although they were positively correlated with mercury levels in the liver. Liver levels were in turn correlated with mercury levels in the ovary. The ratio of mean feather to mean egg concentration ranged from 3.7 to 5.5 according to which feather was used. It was estimated that herring gulls from the Wadden coast ingested between 825 and 1337 microg of mercury in the year prior to analysis. It was also estimated that female birds may excrete over 20% more mercury via their eggs than could be excreted by male birds.