In 1991 we compared eggs, down and body feathers of chicks of Common T
erns, Herring Gulls and Black-headed Gulls in their utility to assess
contamination with mercury. Like eggs feathers distinctly show intersp
ecific and intersite differences in contamination. Highest levels were
found in Common Terns, lowest in Black-headed Gulls. Chicks hatched a
t the Elbe had much higher mercury levels than those in other areas of
the German North Sea coast. Conversion ratios between tissues have to
be used with caution.