Heavy metal poisoning in birds most commonly occurs from ingestion of substances containing lead, or less commonly zinc. Acute heavy metal toxicity is occasionally seen in companion parrots that ingest or chew on objects containing metal because of their curious nature and innate desire to forage. Chronic lead poisoning most frequently affects free-ranging wildlife such as ducks, geese, swans and loons and is most commonly seen during migration in the late fall and early spring. Lead toxicity also occasionally occurs in upland game birds such as mourning doves, wild turkey, pheasants and quail. Lead poisoning has also been reported in raptors, presumably from the ingestion of lead-contaminated prey.