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Abstract

The feathers of seabirds are widely used as appropriate indicators for various aspects of avian ecology and toxicology. To reveal total mercury (Hg) concentrations and the connection to diet using stable isotope analysis in Black-tailed Gulls Larus crassirostris, feathers were collected from 10 carcasses from the breeding colony on Kabushima Island during the incubation period in 2020. Total Hg concentrations in primary remiges were found to decrease during the molt sequence. The innermost primaries (P1), the first to be replaced after breeding, had the highest Hg concentrations of all feathers (7.73 ± 2.37 μg/g dry weight). The concentration of Hg in P1 feathers may reflect the Hg load in birds' body tissues. The outermost primaries (P10), the last to be replaced during primary molt, had not only the lowest Hg concentrations but also the smallest variation among individuals among all primary feathers (1.11 ± 0.29 μg/g dry weight). This property of P10 concerning Hg contamination may be useful when comparing Hg contamination between populations. There were no significant relationships between total Hg concentration and nitrogen isotope ratios (δ15N) or carbon isotopes ratios (δ13C) in most feathers. The lack of a relationship between total Hg concentration and δ15N could be due to low variation in diet during the molt period or to differences between the mobilization of Hg and the incorporation of δ15N into feathers during the period of feather growth. Having less variation in δ13C values among individuals could be due to similarity of locations while the gulls migrate, molting along the way, as well as the irrelevance of total Hg concentration and δ13C values in feathers.

DOI

http://doi.org/10.5038/2074-1235.53.2.1668

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