According to the 1960 research as little as two #6 pellets could or would cause symptoms of poisoning. There again the exposure to the lead shot was dependent on the type of bottom, mud vs. sand/gravel. The mud bottom being better in terms of shot not available to the ducks. Water depth factored in as well. Some recovered if favorable food was available. I'm not familiar with the bottom condition of Klamath or Goose lake. According to the 1960's study weather concentrating ducks in certain areas factored large in creating a die off. It is an interesting read that I will take more time with soon. It starts into the reasoning of how much loss is tolerable, unavoidable? To Keith's point , the lead is certainly still there it has not been cleaned up.
At the time this study was done there was not much of a "green" movement. Mostly state biologists and private concerns looking into what they perceived as a problem. Interesting that there was no conclusion that eating a poisoned duck would be detrimental to a human or other animal.
