These small sized gorgeous cockatoos originate from Indonesia, not Australia as a lot of people think.
Trapping and smuggling these cockatoos, although illegal - still sadly happens. Often the smuggling is internal within Indonesia itself but there is an ongoing trade in wild caught cockatoos throughout the rest of the world.
Birds are frequently smuggled out to Europe.
If you are considering purchasing a cockatoo as a pet, please think carefully. They are SO difficult to keep happy and healthy, they are NOT the same under any circumstances as parrots such as African Greys or Amazon Parrots.
Plus you must take into consideration that many cockatoos, including the Lesser Sulphur Crested or now known as Yellow Crested are CITES Appendix 1 species, meaning they are critically endangered in the wild and as such require an Article 10 certificate accompanying them on purchase to prove they are captive bred from captive bred parents, and NOT wild caught.
Below is a photo of a Lesser Sulphur or Yellow Crested Cockatoo. This photo was taken in a market in Indonesia, you can see the bird is sadly chained to a stand.