A study was conducted on mercury renal concentration in 154 individuals of 28 species of birds with various habitat and trophic preferences. The highest geometric mean concentrations of Hg were found in large piscivorous birds such as Cormorant and Grey Heron. The maximum mercury levels were noted for individuals of White-tailed Eagle and Great Crested Grebe. Significant differences in renal mercury concentration between Sparrowhawk individuals were found in winter and in spring. Male Sparrowhawks generally accumulated rather more mercury in their kidneys than the females. Statistically significant differences in renal mercury concentration between males and females were also found for Goshawks. In gulls, differences in the level of mercury accumulation were dependent on the preferred food.