Heavy metal and selenium levels in Franklin's Gull (Larus pipixcan) parents and their eggs.

Lead, cadmium, mercury, chromium, selenium, and manganese concentrations were measured in the breast feathers of 25 pairs of Franklin's Gull (Larus Pipixcan) and in their eggs from a breeding colony at Agassiz National Wildlife Refuge in Northwestern Minnesota. Metal concentrations in eggs represent metals sequestered in the egg by females at the time of egg formation; while metal concentrations in parents represent concentrations of metals in blood supply at the time of feather formation. There were no significant sexual differences in metal concentrations in feathers, assuming the male to be larger of each pair, but there were significant differences between the concentrations of metals in parents and their eggs. Eggs had significantly higher concentrations of selenium and chromium, but significantly lower concentrations of all other metals than the feathers of their parents. There were few significant correlations among metal concentrations within the egg or within the feather of females, but there were correlations for the feathers of males. Lead and cadmium in feathers were positively correlated for both males and females. Chromium concentrations in eggs were generally higher than reported in the literature. The concentrations in eggs and the feathers of females were positively correlated for mercury, and negatively correlated for chromium and manganese.