The value of chick feathers to assess spatial and interspecific variation in the mercury contamination of seabirds.

In 1991 we compared eggs, down and body feathers of chicks of Common Terns, Herring Gulls and Black-headed Gulls in their utility to assess contamination with mercury. Like eggs feathers distinctly show interspecific and intersite differences in contamination. Highest levels were found in Common Terns, lowest in Black-headed Gulls. Chicks hatched at 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.