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A Mercury Budget for the Bonaparte's Gull during Autumn Moult

Birgit M. Braune and David E. Gaskin
Ornis Scandinavica (Scandinavian Journal of Ornithology)
Vol. 18, No. 4 (Nov., 1987), pp. 244-250
Published by: Wiley on behalf of Nordic Society Oikos
DOI: 10.2307/3676891
Stable URL: http://www.jstor.org/stable/3676891
Page Count: 7
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A Mercury Budget for the Bonaparte's Gull during Autumn Moult
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Abstract

A bioenergetics-based budget which predicts net total Hg loss during the period of autumn moult was calculated for adult Bonaparte's Gulls in the southwestern Bay of Fundy, Canada. Daily food consumption and, hence, ingestion of Hg measured in prey samples, was calculated from estimated energy requirements during the period of moult. The amount of Hg eliminated was estimated from analyses of Hg content in excreta and feathers. Elimination of Hg via the feathers accounted for 68% of the total loss from the body in females and 59% in males during the period of autumn moult. Actual loss from the body over time was estimated as the difference between measured maximum (premoult) and minimum (postmoult) body burden of total Hg. The measured net Hg loss from the body during the period of autumn moult was 23% lower than the predicted value for females and 49% higher than the predicted value for males. The negative and positive deviations of measured Hg losses from the predicted values for the separate sexes averaged out to within 6% of the predicted value when the sexes were pooled.

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