Mercury is the single most toxic element for seabirds. Mercury, along with Cadmium and lead, is one of the heavy metals that are of environmental concern as it can be toxic at levels only moderately elevated above natural ambient levels.
The organic form of methyl-mercury is efficiently taken up by animals and acts as a neuro-toxic compound. The levels found in muscle tissue of different seabird species are lower than critical levels. However, the total mercury concentration is a poor indicator for toxic evaluation, as organic mercury is thought to be more toxic to animals at high tropic levels than inorganic mercury.
In the background data for the contaminant maps we were not able to find any significant difference between regions or species. It is however reported that mercury biomagnifies with the result that species higher up in the food chain have higher mercury levels. The contaminant maps and the background data indicate that cormorant and razorbill have higher levels of Hg than the other birds. These observations are only based on one cormorant and one mean level from five razorbills. Further bird samples are needed in order to make any conclusions. Differences between regions were not found.
Table: Levels Mercury (Hg) in seabird muscles
| Species | Species | Species | |
|---|---|---|---|
 Levels in Black guillemot |
 Levels in Brünnichs guillemot |
 Levels in Common eider |
|
 Levels in Common guillemot |
 Levels in Northern fulmar |
 Levels in Glaucous gull |
|
 Levels in Herring gull |
 Levels in King eider |
 Levels in Black-legged kittiwake |
|
 Levels in Little auk |
 Levels in Atlantic puffin |