Temporal and spatial trends in lead levels in the blood and down of Black Stork nestlings in central Europe.

Young birds at an intensive growth stage are especially vulnerable to the deleterious effects of contaminants such as lead (Pb). This element negatively influences organs, development and even behavior, which can consequently lead to lower survival and reproductive success of the population. There was a suspicion that these mechanisms, along with other factors, retarded population growth of the Black Stork - still a heavily understudied species in respect to pollution, especially Pb. Therefore, we undertook a study concerning Pb concentrations in the down and blood of Black Stork nestlings from breeding grounds in central and southern Poland (Europe). To investigate the effects of Pb exposure on nestling condition, scale mass index and reduced glutathione levels were also studied, but results indicated that Pb did not influence either of these parameters. The highest blood Pb concentration reached 0.247 μg/g, while the highest down Pb concentrations was significantly higher reaching 4.95 μg/g. Concentrations in blood and down were not correlated with each other. Nest location and year of sampling were not influential for blood but were influential for down Pb concentrations. Relationships between Pb concentrations, habitat characteristics and proximity to emitters were not significant. Overall Pb concentrations in Black Stork nestlings were below the toxicity threshold and did not have negative effects on specimens studied. They were probably related to maternal exposure during migration, on stopover and breeding grounds as well as with food provided by parents.