Yes — prickly pear (cactus fruit) is safe and hydrating, with vitamin C and antioxidants. The small seeds are fine; just remove the spines/glochids from the skin.
Keeper's noteBuy it already de-spined, or handle with care. Offer the flesh (seeds are safe). Magenta varieties tint droppings pink — normal.
Why prickly pear is good for parrots
The fruit of the prickly pear cactus is non-toxic and brings vitamin C, magnesium, and fiber, and the de-spined pads (nopales) are edible too. The only real task is handling: the skin carries tiny barbed glochids that must be removed, which is why it's usually sold already cleaned.
How to serve it
Use de-spined fruit; offer the flesh, seeds included.