IMPLICATIONS OF SUBLETHAL LEAD EXPOSURE IN AVIAN SCAVENGERS

The high incidence of lead exposure being reported in avian scavengers is not surprising, considering the frequency with which lead ammunition residues occur in the remains of gun-killed animals. Population impacts likely are underestimated because of latency of effect, low probability of carcass discovery, and the difficulty of detecting the health manifestations of sublethal lead burdens. There are good reasons to expect that sublethal lead is harmful, especially in view of the considerable body of human health literature providing evidence of multiple adverse effects associated with very small amounts of lead, together with the implication that lead physiology is broadly similar among vertebrates. A detailed experimental study of growth and behavior involving closing and controls in developing Herring Gulls (Larus argentatus), and reports of morphological and physiological responses in other species, offer insight into the implications of sublethal lead exposure on wild populations. Further studies of lead's sublethal effects on avian scavengers are therefore warranted and may benefit from advancements in bone-lead measurement and feather analysis, particularly where lead burdens can be benignly assessed among live birds in the field.