Marshmallows are pure sugar and gelatin with no nutritional value. Not toxic, but there's no good reason to feed them — skip them.
Keeper's noteIf you're looking for a soft, fun treat, a piece of banana or a cooked sweet potato cube does the job with actual nutrition. Marshmallows are best left out entirely.
What to watch out for with marshmallow
Marshmallows are essentially whipped sugar. They contain no nutrients a parrot can use, and the sticky texture can be awkward. They're not poisonous, but they're the definition of empty calories, so they don't belong in a bird's diet.
How to serve it
Best avoided — no nutritional value.
Offer banana or sweet potato for a soft treat instead.