In this study, mercury (Hg) concentrations were detected in feathers of 22 bird species from 10 different families living in terrestrial and aquatic ecosystems in Van Lake Basin in Turkey. The mercury rates in feathers were detected based on nutrition status and taxonomic classifications of bird species. Mercury levels were detected in 0.002 +/- 0.007 mg/kg and 2.700 +/- 0.560 mg/kg dry weight range. It was observed that there was a significant difference between the groups classified taxonomically (p < 0.05). The highest concentrations were detected in European Honey-buzzard (Pernis apivorus) 2.7 mg/kg, Lammergeier (Gypaetus barbatus) 0.45 mg/kg and Long-legged Buzzard (Buteo rufinus) 0.28 mg/kg species from Accipitridae family. And the lowest mercury concentration was detected in Golden Eagle (Aquila chrysaetos) from the same family (0.002 +/- 0.007 mg/kg). Mercury was detected in the feather samples taken from the Egyptian Vulture, Lammergeier, Northern Lapwing, and Great Bustard, and these species were determined to be within different endangered categories according to the International Union for Conservation Nature (IUCN). Considering the trophic level (type of food) and systematic groups of the sampled species, it was determined that average mercury level was statistically significant in both cases. It was suggested that the mercury level of the carnivorous ones were higher than that of the herbivorous ones.