They're pretty big, measuring 45 cm (18 in). They're mostly white, with a dark grey (or black) beak, yellow crest feathers on their head (which they sometimes stand straight up) and some yellow under the wings.
Some people think that Sulphur-crested cockatoos make good pets. Perhaps they do. They are cute, intelligent and can be taught tricks. But I don't think that humans make good masters and I don't think that houses make good habitats for cockatoos. When you see them in the wild - what they do - the antics they get up to - you know that it would be criminal to confine them in such an environment.
They're really smart and are often seen playing gregariously in large groups. One game is to hang upside down from a branch high in a rain forest tree, then let go and free-fall in an uncontrolled dive, then at the last minute gracefully fly out of it and up again. They flock in large numbers in the cooler months and take advantage of the plentiful supply of fruit and nuts that we humans have so thoughtfully planted so close together.
Although they are extremely noisy when at play, when raiding fruit trees they will be completely silent. They know very well that they won't get shoosed away if no-one knows they're there.
Another tactic is to bide their time noisily but harmlessly on rain forest trees close by, waiting for an opportunity. The best opportunity comes when the humans have to go out to buy food. Silly humans. It is common in this neighbourhood to come home to find every orange or lemon or other fruit that was growing lusciously on a tree - ready to be picked - lying half eaten on the ground. They look to us like they combine food with fun. Messy and wasteful to us but fun to them.
They will also prune your trees for you. With their sharp beaks, they snip off small branches that come tumbling to the ground outside our verandah. The more birds, the more branches. Sometimes it looks like its raining branches - a branch storm.
We saw half a dozen cockies using an empty coke can as a football once. We were horrified. One of the birds was clearly offside.
Seriously though, we can't help but admire these pesky, noisy, smart, and beautiful birds. This one was caught feasting on the neighbour's pecan tree: