Cockatoos are definitively a type of parrot, belonging to the diverse group of birds recognized by their strong, curved beaks and unique foot structure. This foot arrangement, known as zygodactyly, means they have two toes pointing forward and two pointing backward, providing exceptional grip for climbing and manipulating objects. Like all parrots, cockatoos exhibit high levels of intelligence and social behaviors. Their classification within the broader parrot group is clear, even though they possess numerous distinct features that set them apart from other parrot types.
The Taxonomic Classification of Parrots
The entire group of parrots, including cockatoos, belongs to the biological order Psittaciformes. This order is organized into three major superfamilies: Strigopoidea (New Zealand parrots), Cacatuoidea (cockatoos), and Psittacoidea (true parrots). The family Cacatuidae, which contains all cockatoo species, is the only family within the superfamily Cacatuoidea.
This hierarchical structure confirms that cockatoos are a distinct evolutionary lineage nested within the overarching parrot order. The true parrots, such as macaws, conures, and African greys, are grouped separately in the superfamily Psittacoidea (Family Psittacidae). This classification reflects that cockatoos branched off early in parrot evolution. While the Psittaciformes order is distributed globally, the cockatoo family is primarily centered in Australasia.
Defining Physical Features of the Cockatoo Family
Cockatoos are physically distinguished from true parrots by several unique characteristics. The most obvious difference is the presence of a prominent, movable crest of feathers on the head, which can be raised or lowered to communicate excitement or alarm. While some true parrots have head feathers that can be slightly raised, the large crest of the cockatoo is unique to the Cacatuidae family.
Another differentiator is the presence of “powder down” feathers, which disintegrate into a fine, talc-like keratinous dust. This powder is used to preen and waterproof the plumage, a trait present in cockatoos but rare in true parrots. Cockatoo coloration is also notably different, as their plumage is generally less vibrant, predominantly consisting of white, black, or grey, often with patches of yellow, red, or pink.
This reduced color palette is due to the lack of a feather structure known as the Dyck texture, which scatters light to create the iridescent colors seen in many true parrots like macaws. Furthermore, cockatoos possess a gall bladder, an organ that is often absent in the true parrots of the Psittacidae family. These physical and internal traits mark the Cacatuidae family as a biologically separate group.
Major Groups of Cockatoos
The family Cacatuidae comprises 21 recognized species, which are generally divided into major groups across seven genera. These groups vary significantly in size, color, and geographic range, though all are found within the Australasian region.
The major groups include:
- The White Cockatoos, belonging to the genus Cacatua, which includes the Umbrella Cockatoo (Cacatua alba) and the Sulphur-crested Cockatoo (Cacatua galerita). They are characterized by mostly white plumage and large crests.
- The Black Cockatoos, encompassing five species in the genus Calyptorhynchus, such as the Red-tailed Black Cockatoo. These birds are larger and have darker plumage with colored tail panels.
- Corellas, such as the Little Corella (Cacatua sanguinea), which are smaller white cockatoos with shorter bills.
- The Galah (Eolophus roseicapilla), unique for its distinct pink and grey coloration.
- The Palm Cockatoo (Probosciger aterrimus), the largest species, recognizable by its huge bill and bare, red facial patches.
- The Cockatiel (Nymphicus hollandicus), the smallest member of the family, which represents one of the earliest branches in the cockatoo evolutionary tree.