Ducks and geese are omnivores. If they think it looks interesting, they will try to eat it. This especially includes shiny things like coins, staples, nails, scrap metal, and the like. Obviously, this is not good for their health and can cause some severe problems. The issues caused by the ingestion of metals is collectively known as Hardware Disease.
While the objects themselves can cause damage, such as a sharp nail piercing the lining of the stomach, it is the poisoning from the metals as they breakdown that is the real problem. Symptoms include but are not limited to:
Loss of appetite
weakness and lethargy
bright green or bloody droppings
Poisons are typically fast-acting and once symptoms begin to show they should be treated quickly by a veterinarian. We have a list of veterinarians by state on our website that are knowledgeable in waterfowl care. If a veterinarian is not on hand or not feasible, there are some things you can do to help. Countryside Daily suggests feeding your ducks molasses or charcoal pills to flush out the toxins. Lisa Steel of Fresh Eggs Daily advocates more for prevention, though she does list several herbs such as bay leaves, dill, sage, and thyme mixed as a salad to help detoxify. For objects that would not pass naturally, such as a metal springs or larger pieces of glass, they will require surgery.
The best way to prevent hardware disease is to remove any potential objects your birds might eat. This means monitoring the pen or pasture for anything they might dig up or find. If there has been a building project, make sure all screws, nails, and staples are picked up. To be very thorough, a metal detector would be of help.