MP12 Organic, Metallic, Organometallic Pollutants
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(HEI-1115-845624) Species differences in sensitivity of birds to methylmercury.

Heinz, G¹, Hoffman, D¹, ¹ USGS Patuxent Wildlife Research Center, Laurel, MD, USA

ABSTRACT- Many species of birds live in aquatic habitats that are contaminated by mercury. Methylmercury is the predominant chemical form of mercury in the foods of aquatic birds, and this form is highly toxic to avian embryos. Therefore, avian reproduction is considered to be a sensitive indicator of mercury pollution. The reproductive success of some avian species, such as the common loon, is thought to be sensitive to mercury contamination, and estimates have been made of the levels of mercury in the diet and eggs of loons that may cause harm. Unfortunately, little information is available from the field to determine the sensitivity of other avian species to mercury contamination. More field research is need for other species, but controlled studies in which captive pairs of breeding birds are fed different levels of methylmercury is another way differences in species sensitivity can be studied. However, given the great cost and time required to conduct controlled feeding studies with wild birds, few such studies are likely to be carried out. Consequently, concentrations of mercury in eggs considered to be harmful have come mostly from controlled laboratory studies with species such as game farm mallards and ring-necked pheasants. How the sensitivity of the game farm species compares to that of wild birds is unknown. We have been using egg injections to compare the embryo sensitivities of many wild birds to methylmercury, and this technique has shown that some species are more sensitive than the game farm species. Combinations of field studies, captive feeding studies, and egg injections will be needed to arrive at a more complete picture of how birds may differ in their sensitivity to methylmercury.

Key words: mercury, birds, reproduction, egg injections