The short answer

Yes — celery is safe, but slice it thin to remove the strings, and offer the leaves too.

Why

Celery is hydrating and harmless, but its tough stringy fibres can be a choking hazard for a tiny beak. The leaves are actually more nutritious than the stalk.

How to feed it

Slice the stalk thinly across the grain to cut the strings, or simply offer the leaves.

How much & how often

Frequent is fine.