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[Mr. 16 gauge]

is pueter toxic i have read were early bp hunters would melt down the cups and plates and they would shoot like lead

Is pewter toxic? How is this for an answer: "It depends"
Pewter had been suggested as an alternative bullet material on other traditional black powder websites when all the condor hulaballo started, but there are two problems with it: 1.) the USFWS has to "approve" it as a nontoxic substance prior to it being allowed and 2.) from what I can gather on the net, 'pewter' can be made via various formulas; it consists of primarily tin, with any or some of the following metals added: lead, antimony, copper, and silver. Most pewter alloys that are considered 'nontoxic' for human use consists of eating utensils...cups, plates, forks, ect. It has been stated by others that foods with acids, such as cider, vinegar, ect in them can leach out the lead and antimony (both are dangerous heavy metals) and allow it into the body.
But remember, we are talking about a bird eating a spent round, and while I don't know much about condors, I am assuming that they are similar to vultures, and if you've seen some of the crap that vultures eat, it stands to reason that they must have some pretty powerful stomach acids to digest that stuff w/o succumbing to it. So I would suspect that any pewter would be found to be toxic to the birds unless it was a pure tin/silver mix, which would obviously be too expensive to shoot.