Examination of mercury concentration in the feathers of 18 species of birds in southwest Iran

This paper presents the levels of mercury (Hg) in tail feathers from different species of birds, in southwest Iran (Khuzestan to Persian Gulf). Between April and October 2005, we collected tail feathers from 77 birds belonging to 18 species, mostly raptor birds. The birds were collected for the Museum Natural History, Faculty of Natural Resources and Marine Sciences of Tarbiat Modares University. Hg concentrations were evaluated in relation to taxonomic affiliation and trophic level. Feather Hg concentrations ranged from 0.09 to 2.01 mg/kg dry wt. We found a significant difference in feather Hg concentrations across taxonomic groups (p<0.001) with highest concentrations in common kestrel and saker falcon (Falconidae) (1.87 mg/kg) followed by greater spotted eagle, sparrowhawk, goshawk, griffon vulture, buzzards, marsh harrier (Accipiteridae) and owls (Strigidae). Blue-cheeked bee-eater (Meropidae) had intermediate values, followed by European roller (Coraciidae), and lapwing (Charadiidae), whereas black francolin, see-see patridge and chukar (Phasianidae) (0.18 mg/kg) contained the least amount of Hg. There was a significant difference in feather Hg concentrations in relation to trophic levels, at confidence level of 99% (p<0.001). There was an increased pattern in the amount of mercury from herbivorous birds up to vertebrate predators, so that the amount of mercury in vertebrate predators (1.30 mg/kg) was more than 1.5 times as much of the invertebrate predators (0.7 mg/kg) and more than 6 times as much of the herbivorous birds (0.18 mg/kg). We also measured Hg levels in secondary feathers of raptor birds. Paired samples t-test showed that the concentrations of mercury were significantly higher (p<0.001) in the tail feathers (1.2 mg/kg) than secondary (0.71 mg/kg). However, Hg levels are below the range found by other authors to cause behavioral change or reduce reproduction (5 mg/kg). It seems that exposure of some birds with mercury for a long time causes their high concentration of mercury.