Every species of cockatoo is different, even every individual is different! Still something can be said about the general behavior of cockatoos in the wild.
Every species of cockatoo lives in pairs of in groups, there are no solitary species. The group is used for safety and finding food, as more eyes spot predators and food quicker. The need to be part of a group is innate to cockatoos, just like horses, dogs and people are naturally drawn to being part of a group.
Within the group in which the cockatoos live, there is a lot of social contact between the members. Almost incessantly cockatoos stay in contact with each other by screaming to each other. Cockatoos can recognize the screams of their relatives and other group members, just like we recognize voices. When resting the social contact takes the form of grooming: gently touching and cleaning the feathers of other cockatoos of the group. This maintains the social bonds in the group and also results in beautifully maintained feathers. Cockatoos are even unable to properly groom their own crest feathers, being dependent on conspecifics to do this for them. Especially cockatoos that are part of a pair will groom each other often and for long periods of time.
Cockatoos choose a mate for life. As long as both partners are alive, they stay together. Even when one of them dies, the other very often stays alone for the rest of its life. Young cockatoos will find a mate within their group. First they get to know their peers when they are developing into adults. Once they are sexually mature, they will find a mate and spend a lot of time which this special bird. They will groom each other, sleep next to each other, forage together… When the pair bond is formed, it will not be broken. They will raise young together, in which both the male and the female will incubate the eggs and will bring food for the chicks. It seems very monogamous and idyllic, but this is not the complete truth. Cockatoos are socially monogamous, but DNA tests reveal that not all offspring in a nest are from the father that raises them…