how do you tell if a cocateel is a female or male?

Answer 1

Look at the feathers under the tail and wings. They will have stripes and bars if it's a female, and solid if a male. This only applies to cockatiels who have molted and are at least 6 months old. If younger, the vet can do a simple DNA test.

Answer 2

the only way is from a blood sample, from what I have heard.