Abstract
Individuals with higher contaminant burdens are expected to be in poorer physical health and be of lower individual body condition and energetic status, potentially resulting in reduced ornamentation or increased asymmetry in bilateral features. The degree and magnitude of this effect also would be expected to vary by sex, as female birds depurate contaminants into eggs. We tested for relationships among mercury in feathers, sex, and elaborate feather ornaments that relate to individual quality in crested auklets (Aethia cristatella), small planktivorous seabirds in the North Pacific Ocean. We found no relationships between mercury and the size of individuals' forehead crest or degree of measurement asymmetry in auricular plumes, both of which are favoured by intersexual selection. Females had significantly greater mercury concentrations than males (females. 1.02 ± 0.39μg/g; males, 0.75 ± 0.32μg/g); but concentrations were below that known to have physiological effects, as expected for a secondary consumer. Sex differences in overwintering area for this long-distance migrant species (more females in the Kuroshio Current Large Marine Ecosystem than males) could be the reason for this seemingly counterintuitive result between sexes. Further research relating mercury burden to overwintering ecology and diet contents would build on our results and further elucidate interrelationships between sex, sexually selected feather ornaments and contaminant burden.
Highlights
Mercury (Hg) is a pervasive global contaminant that is largely produced anthropogenically, and projected to increase into the future (Driscoll et al 2013; Krabbenhoft and Sunderland 2013; Lamborg et al 2014; Lindberg et al 2007; Selin2014; Streets et al 2009)
The model for predicting feather Hg that included sex received the most support; no other model had ΔAICc < 2, and models that included ornaments were not competitive (ΔAICc < 9.8; Table 1), so results are from the top-ranked model only
We found higher Hg concentrations in female Crested Auklets than males at
Summary
Mercury (Hg) is a pervasive global contaminant that is largely produced anthropogenically, and projected to increase into the future (Driscoll et al 2013; Krabbenhoft and Sunderland 2013; Lamborg et al 2014; Lindberg et al 2007; Selin2014; Streets et al 2009). Birds are effective monitors of Hg in the environment, because they can integrate signals over space and time, Hg in tissues is dietary in origin, and tissues can be sampled non-destructively (Monteiro and Furness 1995; Monteiro and Furness 2001; Monteiro et al 1998). Birds regulate their Hg body burden by excreting the toxic form of
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