I have received an answer! I copy & paste below.
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Hi Ann,
We don't know of any studies that have addressed this. We all drink water that runs through copper pipes every day. It is not nearly as dangerous as 100 other substances that are probably hiding in much of our drinking water.
We would err on the side of caution and not go overboard. Adding Apple cider vinegar is also a trick that everyone seems to swear by (we don’t have any research on this either, but it would not be harmful).
Marc
Marc Devokaitis
Public Information Specialist
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Cornell Lab of Ornithology
159 Sapsucker Woods Rd
Ithaca, NY 14850
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I would certainly stick with the earlier dated pennies to stay away from the zinc. Zinc is certainly harmful to birds! Or just use a piece of copper tubing that is rated for use as water lines for humans.
I have submitted a tip regarding the apple cider vinegar. From all I found about it, you use 1 tsp. per gal. of water or 1 cap full & it has the added benefit of providing vitamins & minerals to the birds.
I plan to experiment to see which works best for me; the copper tubing or the apple cider vinegar.
