Breeding Success of Osprey under High Seasonal Methylmercury Exposure
Osprey (Pandion haliaetus) commonly breed in northern Québec, often near reservoirs where 4 to 6 fold increases in fish mercury (Hg) levels have been noted following flooding. With the exception of eggs, which are usually laid when reservoirs are still ice covered, total Hg levels were significantly higher in the feathers of adult Osprey and nestlings living close to reservoirs than in those living in a natural environment. Despite a much higher total Hg exposure for Osprey fishing in reservoirs, the number of young fledged was not statistically different between nests located near reservoirs and those located near lakes and rivers. Our results suggest that growing feathers, either in molting adults or in nestlings, provide a good excretion route for total Hg. Nevertheless, the good breeding performance of Osprey nesting near reservoirs cannot be explained solely by the partial molt that adults undergo in summer. Future research on methylmercury (MeHg) exposure through fish consumption and on post-fledging risks related to high Hg exposure during the preceding fall migration must address the physiological mechanisms, such as demethylation by internal organs, that allow piscivorous birds to regulate MeHg in their bodies.
KeywordsClutch Size Breeding Success Environment Canada MeHg Concentration Active Nest
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