Lead is a highly toxic heavy metal that is found in many types of ammunition and fishing tackle. Lead toxicity in wild birds occurs when they accidentally consume a source of lead through their normal feeding habits. Ingestion of lead from spent hunting ammunition or fishing tackle can cause illness or death in wild birds. Death from lead toxicity has been documented in Wisconsin in bald and golden eagles, common loons, trumpeter swans, turkey vultures, waterfowl and a whooping crane.
Eagles can accidentally eat lead fragments found in the gut piles and carcasses of deer harvested with lead ammunition. Loons pick up small pebbles from the bottom of lakes as a part of their normal behavior to add grit to their crop (the upper part of their digestive tract) and frequently mistake lead fishing weights for small stones. Trumpeter swans feed by stirring up the bottom of lakes and accidentally eat lead fishing weights or spent lead shot pellets. Lead that is consumed breaks down in the stomach and is then transported through the blood. The lead is then absorbed into tissues, such as the liver, kidneys and bone.
Birds exposed to sudden high levels of lead can die suddenly with no signs. Birds that suffer from slow longer-term exposure to lead can show signs of weakness, loss of muscle mass and fat reserves, green diarrhea, incoordination, paralysis or convulsions. Long-term effects of lead exposure can alter the behavior and survival of birds.
In 1991, the US Fish and Wildlife Service launched a nationwide ban on lead shots for waterfowl hunting to reduce the number of lead shots falling into lakes. The Department has prohibited the use of lead shots for hunting mourning doves on state-managed lands since the inception of dove hunting in Wisconsin in 2003.
Hunters wanting to help reduce the loss of wildlife from lead toxicity can switch from using lead ammunition to non-toxic ammunition for all their hunting activities. People who fish can purchase non-lead fishing tackle and dispose of their lead tackle by taking it to a recycling facility that accepts and properly disposes of lead. Other wildlife enthusiasts can help by sharing information with their family and friends on the dangers of lead to wildlife.
Lead can accidentally be consumed by people when eating wild game that was harvested with lead ammunition. Deer harvested with lead bullets have been shown to have tiny lead fragments remaining in the processed meat which can be found far from the wound created by the bullet. These fragments are often too small to be seen, felt or noticed when eating the meat. While it has not been documented that lead fragments found in the wild game caused illness in humans, some precautions found in the link below are advisable.