| Summary: | Mercury pollution is a global issue due to atmospheric transport and its bioaccumulation by organisms, resulting in several adverse effects on wildlife. Migratory shorebirds use several wetlands at different latitudes where mercury pollution is likely to differ. Little is currently known about mercury levels in shorebirds in tropical regions. In this study, we assessed mercury levels in freshly grown feathers of several shorebirds species wintering in two important wetlands of East Atlantic Flyway: Bijagós Archipelago (tropical; Calidris alba, Calidris canutus, Charadrius hiaticula, Tringa totanus, Actitis hypoleucos, Arenaria interpres, Calidris ferruginea and Pluvialis squatarola) and Tagus Estuary (temperate; Calidris alba, Calidris canutus, Charadrius hiaticula, Tringa totanus, Calidris alpina and Limosa limosa). We also assess mercury levels of breeding species, by analysing eggshells of Charadrius alexandrinus and Himantopus himantopus, collected in saltpans of the Ria de Aveiro and of the Tagus Estuary, and in the faeces of the last species collected mostly throughout the non-breeding season. Mercury levels in feathers and eggshells varied significantly among species and wetlands. The results showed that, in general, shorebirds wintering in Tagus Estuary had higher mercury concentrations (2.106±0.681 – 9.918±3.499 ppm) than those from Bijagós Archipelago (0.932±0.369 – 2.773±0.784 ppm), suggesting that mercury exposure is higher in this temperate wetland. Charadrius alexandrinus eggshells had higher concentrations in both portuguese wetlands (0.034±0.006 e 0.037±0.006 ppm) than Himantopus himantopus ones (0.018±0.004 e 0.009±0.002 ppm). The Himantopus himantopus faeces contained detectable mercury but the mean concentrations (0.040±0.003 – 0.085±0.025 ppm) did not vary over the season. The differences observed in this study were likely caused by spatial differences in mercury pollution between wetlands and by interspecific differences on trophic habits of species. Overall, mean mercury levels in feather ...
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