Cockatoos can live as long as 100 years, and it's impossible to tell how old an adult is with accuracy unless the bird has a leg band with his year of birth. The birds show no external signs of aging, and only you can, however, tell if your cockatoo is a juvenile or an adult just by looking at him.
How to Tell the Age of a Cockatoo
A Bird in the Nest
A cockatoo nestling is fully dependent upon her parents for the first 56 to 96 days of life, depending upon which breed she is. She hatches out of her egg with eyes closed and may or may not have down, depending on species. At about 3 weeks, her eyes will open. By 25 days old, down becomes patchy as feathers push their way into place. Halfway through her nestling phase, she'll be fully feathered, although wing and tail feathers are not yet fully mature. She'll spend the last few weeks under her parent's care strengthening her wings to become independent.
Ready to Reproduce
Both female and male cockatoos look alike, making it hard to tell apart from a distance even when they reach sexual maturity at about 2 years old. When a female is sexually mature, her eye color changes to reddish brown, making it easy to tell males from females up close.