The latest report from the Predatory Bird Monitoring Scheme has focused on the use of raptor tissues and eggs to inform our understanding of trends in mercury (Hg) concentrations in our environment.
The study found that residues of mercury in sparrowhawk livers vary with age and sex, with concentrations being highest in adult males. Starvation in the birds examined also elevates liver mercury concentrations but there has been no consistent upward or downward trend in mercury residues since 1990.
The study has allowed the scheme to set current baseline mercury concentrations in sparrowhawk livers and golden eagle eggs. These baseline levels will be used to assess changes in future exposure to this toxic metal in terrestrial lowland (sparrowhawk) and upland habitats (golden eagle).
In addition, the report investigated the use of alternative tissues and species for our monitoring. We found that mercury concentrations in brain, kidney and liver tissue were highly correlated but that brain or kidney may be better target organ for mercury monitoring than liver. We also found that that sparrowhawks (which feed on birds which themselves are relatively mobile) are as likely as kestrels (which feed on less mobile small mammals) to be representative sentinels of changes in environmental exposure to mercury in lowland systems.