Mercury concentrations in feathers of Common Swifts (Apus apus)

Mercury (Hg) has been well studied as a bioaccumulated contaminant in aquatic ecosystems worldwide. It has been found to have negative effects on carnivorous and piscivorous bird species with the highest Hg concentrations at the top of the food chain. The objective of this study was to increase our knowledge of mercury exposure in insectivorous birds, especially in a species of the family Apodidae. The Common Swift (Apus apus) that specialises on feeding on aerial plankton molts and winters as a long-distance migrant in Sub-Saharan Africa. In the breeding seasons 2011-2013 the concentrations of Hg in primary flight feathers (P8-P10) in juvenile (n = 35) and adult (n = 25) injured Common Swifts were examined in the area of Hannover, Lower Saxony, Germany using cold vapour atomic absorption spectrometry. As a first reference, it was possible to determine feather Hg levels in adult (Mean ± SD: 0.53 mg/kg wet weight ± 0.37; Xmin-Xmax: 0.04-1.45 mg/kg; n = 25) as well as in juvenile Swifts (Mean ± SD: 0.11 mg/kg wet weight ± 0.06; Xmin-Xmax: 0.04-0.25 mg/kg; n = 35). The significant differences between the ages (p ≤ 0.001) are probably caused by differences in the feather growth, in accumulation of mercury for a longer time in adults as well as particularly in differences between mercury pollution in breeding and wintering ground. The mercury levels detected in swifts in this study are all below the range found by other authors to cause behavioural changes or reduced reproduction (5 mg/kg).