LEAD CONCENTRATIONS IN BIRDS OF PREY IN BRITAIN

This paper reports on lead (Pb) concentrations in the livers of 424 in dividuals of 16 raptor species found dead and sent for analysis to the Institute of Terrestrial Ecology, Monkswood, from the early 1980s to the early 1990s. Elevated Pb concentrations in liver (>20 ppm dry wt), within the range associated with Pb poisoning mortality in raptors, w ere recorded in one peregrine (4% of species sample) and one buzzard ( 2% of species sample). These birds are likely to have ingested lead gu nshot in the fresh of their prey. Another one each of these species ha d liver Pb concentrations of 15-20 ppm dry wt, reflecting unusually hi gh absorption of Pb. No individuals of any other species had >15 ppm d ry wt liver Pb, although some had 6-15 ppm. The source of Pb in these birds was unknown, but it could have resulted from high Pb concentrati ons in prey items, including some containing lead shot. Median liver P b concentrations were generally very low (ranging from Pb <0.07 to 1.6 1 ppm dry wt for species with sample sizes exceeding 10). In sparrowha wks, for which a large sample was available, liver Pb concentrations i n all but one individual were low (<2.6 ppm dry wt). Pb concentrations in juveniles were significantly lower than in adults, and were lowest in recently fledged birds.