Lead poisoning in waterfowl is extremely unique and is exclusive to certain species of ducks, swans and geese. While lead ammunition used for hunting waterfowl was banned in 1992, this was predominantly due to the aquatic environment in which the animals reside, and the unusual manner in which the species eat.

Waterfowl generally congregate in and around bodies of water, where lead shot can accumulate in the sediments of water bodies that are heavily hunted. The accumulation of shot can become problematic because of the non-selective way in which waterfowl feed. By sticking their head underwater and blindly sifting through sediments for seeds, bugs, etc., waterfowl can unintentionally ingest large amounts of shot.

The ingestion of shot is further compounded by the waterfowl’s unusual digestive physiology. Waterfowl have a very specialized gizzard that acts as a mechanical “grinder” to break down food items by muscular contraction and grinding of food against the sand/rocks within the gizzard. Waterfowl also consume harder food items like mollusks and hard shelled seeds to assist in the digestion of food. Within the gizzard of waterfowl, food is combined with sand, rocks, and, if swallowed, shot, which causes the lead to be ground down over a long period of time and become bioavailable to some extent.

Waterfowl present a unique circumstance not found in upland hunting. The combination of these unusual events in which a high concentration of lead shot accumulates in an aquatic environment, coupled with the non-specific feeding habits of waterfowl and the unparalleled processing and digestion of food makes waterfowl unique.

However, these circumstances, while unique to waterfowl are not an issue in non-aquatic situations, (ie upland game hunting practices), because lead shot is dispersed over a large area and embeds in the soil where it is not readily available for ingestion by wildlife. Furthermore, upland game birds do not commonly ingest lead shot. In those rare instances where upland birds do ingest lead shot, they do so while ingesting food items which stimulate the digestive process which causes the bolus of food to be rapidly swept out of the stomach, without a significant absorption of lead.