They have strong legs, and clawed zygodactyl feet (with two toes facing forward and two toes facing back) that are very useful to climb up trees. Many parrots are vividly coloured, and some are multi-coloured. The plumage of cockatoos ranges from mostly white to mostly black, with a mobile crest of feathers on the tops of their heads. Most parrots exhibit little or no sexual dimorphism.