Lead Poisoning in Migratory Birds

Lead Poisoning is an intoxication, caused by the absorption of hazardous levels of lead in body tissues. Ingested lead pellets from shotgun shells are the most common source of lead poisoning in birds; other sources include lead fishing sinkers, mine wastes, paint pigments, bullets and other swallowed lead objects.

Lead Poisoning affects every major species of waterfowl in North America and has also been reported in a wide variety of other birds, particularly eagles. Eagles and other raptors generally get lead poisoning as a result of swallowing lead shot embedded in the flesh of their prey. Reducing the magnitude of losses from lead poisoning requires denying birds use of problem areas and rigorous pickup and disposal of dead and terminally ill birds.

Clinical/Field Signs
Lead poisoning is considered a chronic disease in wild birds. Sick and dead birds are usually observed in low numbers, if at all. Large scale mortality due to lead poisoning occurs rarely. Birds are often mistaken for cripples during or after the hunting season. Signs include: lethargy, progressive weakness, green-stained feces and vent (cloaca) due to bile staining, a reluctance to fly or inability to sustain flight, and weight loss leading to emaciation. Severely affected birds often do not have an escape response but will usually seek isolation and cover, making them difficult to find. Green-colored feces can be seen in areas used by lead-poisoned waterfowl.

Lesions
Emaciated birds with severe wasting of breast muscles. Impaction of esophagus and/or proventriculus containing food, sand, or mud. Enlarged gallbladder containing thick, dark green bile. May see bile staining (green color) in the gizzard and/or around the vent. Gizzard may or may not contain lead fragments. These lesions are similar to what is seen in starvation. The diagnosis is confirmed by detecting toxic levels of lead in the liver.

Wildlife Management Significance
Losses occur nationwide, usually in winter or early spring (after the hunting season). Waterfowl on high corn or grain diets have an increased sensitivity to lead. Identifying the lead source and reducing its availability through discing or reclamation will help minimize losses. Use of nontoxic shot is a good long-term solution for reducing losses.

For more information on this or any other wildlife health issue, please contact the National Wildlife Health Center at 608-270-2400.