Yes, with care — human-grade, shelled, unsalted peanuts are okay as an occasional treat. The risk is aflatoxin, a mold poison that causes liver disease in birds.
Peanuts themselves are not toxic; the danger is Aspergillus mold, which produces aflatoxin and thrives inside peanut shells — especially in bulk bins and bird-feed-grade nuts. Chronic low-dose exposure causes liver disease; a moldy nut can cause acute poisoning. Peanuts are also fatty enough to crowd out better foods.