Bird tissue residues, mercury

Tissue residues of mercury, as methylmercury, considered harmful to adult birds ranged between 8.0mg/kg FW in brain to 15.0 in... 

For threatened or endangered species, or species of special concern, it is often necessary to analyze specimens that have died of causes not directly attributable to mercury. Bird eggs that have been abandoned or flooded out may be used for analyses. However, if the eggs were pushed out of the nest by parents that are incnbating the rest of the clntch, the reason for rejection of the egg must be considered in order to properly interpret mercury residue levels. Similarly, birds killed by predators may be suitable for analysis, but the internal tissues of sick or emaciated birds should not be nsed for residue analysis because in some studies, error has resulted from remobilization of mercury (Ensor etal. 1992 Sundlof etal. 1994). 

Finley, M.T., W.H. Stickel, and R.E. Christensen. 1979. Mercury residues in tissues of dead and surviving birds fed methylmercury. Bull. Environ. Contam. Toxicol. 21 105-110. 

The tissues and eggs of ducks and other species of birds collected in the wild have sometimes contained levels of mercury equal to, or far exceeding, those associated with reproductive and behavioral deficiencies in domestic mallards (e.g., 9.0-ll.Omg/kg in feathers and >2.0 mg/kg in other tissues) therefore, it is possible that reproduction and behavior of wild birds have been modified by methylmercury contamination. Tissue mercury residues of wild-strain mallards and game-farm mallards were not significantly different after the birds were fed diets containing 0.5 mg Hg/kg as methylmercury for extended... 

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