Plain peanut butter is okay as an occasional treat — but check the label first: any peanut butter containing xylitol is potentially deadly, and many add salt and sugar.
Keeper's noteONLY plain peanut butter whose label is just 'peanuts' (maybe a little salt). Never anything that lists xylitol or 'birch sugar'. A thin smear is enough — it's calorie-dense and gluey.
What to watch out for with peanut butter
Peanut butter itself is just ground peanuts (see the peanut entry for the aflatoxin note), but two label hazards make it a caution. First and most critical: some 'sugar-free' or 'no added sugar' peanut butters contain xylitol, an artificial sweetener that is dangerous to birds. Second, most commercial brands add salt, sugar, and oils. It's also very sticky and fatty.
How to serve it
Read the label: reject any product containing xylitol/birch sugar.