Methyl mercury is a contaminant of concern in many aquatic and terrestrial habitats. Methyl mercury bio-magnifies within food chains resulting in higher trophic level species, like the American kestrel (Falco sparverius), having greater concentrations than the prey upon which they feed. It is hypothesized that low-level exposure to methyl mercury causes immunosuppression in adult kestrels and hinders development of the immune system in young birds. Three phases of study involving captive-bred kestrels will be used to measure immunosuppressive effects. Phase I will test the ability of adult, non-breeding kestrels to elicit innate (a fast-acting but temporary response to any foreign entity), and adaptive (a slow-acting but long-term response involving antibody production) immune responses following low-level exposure to methyl mercury in their diet. A dose-response relationship will be established at concentrations lower than those required to produce overt signs of toxicity, closely mimicking exposures commonly encountered by free-living kestrels. Phase II will assess the effects of methyl mercury on the developing kestrel's immune system. Egg production provides a unique opportunity for studying immune system development because embryos acquire the benefits of maternal antibodies, but young birds are hatched prior to the complete development of their immune system. The development of the immune system, including the production of T cells and B cells, continues for several weeks post-hatch while kestrels are still in the nest and dependent upon their parents' for food. Phase III will investigate a specific immune response of adult kestrels to a known microbial pathogen following chronic exposure to methyl mercury in the diet. Pathogens are a common stressor encountered by wildlife, particularly those feeding on live prey.
