Some large parrots like cockatoos become quite aggressive toward perceived intruders in their territory, even going so far as to fly and bite people when out of the cage.
I have worked with a few of the larger birds, but many more of the triton cockatoos (Cacatua galerita triton), which behaviorally are a bit different. I have known excitable Galerita galeritas (sulphur crests) but generally, they seem more mellow. Out of all the family parrots I have worked with, tritons have been the most clever and mischievous. (Because of their intelligence, tritons are often used to perform in bird shows.)
Having such a large and intelligent parrot in your household means that you need to maintain control over his outgoing and exuberant tendencies. You are not just the caregiver but also a guidance counselor to what could be described as a very precocious child.
Teach your cockatoo tricks that you can then later use to redirect your bird's attention to something postive.
Keep It Under Control
Make sure your cockatoo is securely placed in its cage prior to visitors entering the home. The energy levels are high for everyone when someone first enters the home, and the dynamics of the group has changed. This is especially true for a male cockatoo that has decided that he is the welcoming committee and must see if this "intruder” is friend or foe.
When people respond in a timid or fearful way, the bird’s natural response is to bite them, whether it is from fear or aggression. Unfortunately, this has become a pattern that must be broken. All that energy and intelligence must be redirected into more suitable actions.
The Magic Of The Neutral Room
Spend some time each and every day working with your big guy one-on-one in a neutral room. This is an unfamiliar room where he doesn’t have to protect his perceived territory.
Become his teacher, and train him to do some natural behaviors on cue. This could be as simple as waving by raising his foot, or as complex and fun as dancing and spreading his wings. These parrots are extremely dexterous and can manipulate objects for hours. Some tricks might be to put a nut on a bolt or stack some rings on a peg, etc. These daily sessions will strengthen your role as flock leader and will also build his self-esteem.
If your guests are willing and you prepare them for the "show,” bring out your performer and, maintaining control, have him do a trick or two. Once the "drama” of their reactions has turned from surprise and fear to applause and praise, he will become easier to control. When you see him getting wound up or agitated, give him his cue to do a trick. The diversion will circumvent the undesired behavior.
This is a prime example of a bird in charge of his own life and doing a bad job of it. He desperately needs some guidelines and a way to use his extraordinary intelligence to entertain himself and others without getting into trouble. He’ll be happier and easier to manage as a proud star than as an insecure spoiled brat.