Bioaccumulation of metals in a critically endangered migratory songbird, the Yellow-breasted Bunting (Emberiza aureola)

The bioaccumulation of metals can cause negative effects on health status and body condition in wildlife. However, research in this field is strongly biased towards Europe and North America. Here we investigate metal and metalloid concentrations in feathers of a once common but now critically endangered migratory songbird, the Yellow-breasted Bunting Emberiza aureola. Feathers were sampled in Thailand but most likely moulted in China, where the species stops over during migration, and therefore likely relate to background pollution levels at these stopover sites. We detected chromium, copper, manganese, iron, lead, tin and zinc in 100% of the samples, whereas arsenic was detected in 9% and mercury as well as cadmium in 2% of the individuals. Most importantly, we found a weak but significant negative association of zinc concentration and individual body condition. Lower body condition could limit successful migration and ultimately lead to higher fitness costs and reduced survival in this threatened species. We call for studies to investigate whether elevated zinc exposure in Yellow-breasted Buntings is linked to mining activities or to the recent increase in zinc-biofortified rice planted in Asia to combat human zinc deficiency.