Lead shot, just a few pellets eaten as grit can and will kill waterfowl. There have been examples of waterfowl dying from lead poisoning for years prior to the banning of lead shot for waterfowl. Areas that were heavily shotover had literally tons of lead on the bottom and in shallow areas it is easily accessible to be eaten by waterfowl. I participated in the studies that were done in areas heavily hunted for ducks and geese. I collected hundreds of gizzards and livers from waterfowl killed by waterfowlers on Susquehanna river above safe harbor dam in Lancaster Co. PA. Others in heavily hunted areas of PA did the same kind of collections across the state. When those gizzards and livers were studied the number of gizzards that contained at least one lead shot and the number of livers that contained lead was astounding. I can't speak for lower reproduction because of lead but I doubt it is because of lead shot because it doesn't take much ingested shot to kill a duck, I would rather believe it is because of lead from others sources in the environment. I wasn't pleased when the ban on lead shot was coming to fruition, mainly because the first steel shot was junk, some of the Remington shot was actually joined by a piece of wire from which it was made. I went to Bismuth as soon as it came out and I haven looked back. However, there is no doubt that the disconuing use of lead shot from waterfowl has saved a lot of waterfowl from death from lead poisoning.