the Red-Tailed Black Cockatoo,

the Carnaby's (Short-Billed White-Tailed Black) Cockatoo,

and
the Baudin's (Long-Billed White-Tailed Black) Cockatoo,

all with their cockatoo crests up high.

One plus one plus one makes three of us!

And they went to stand behind the Regent Parrot.

All right, said the Regent Parrot, how many other kinds of cockatoos are there in Perth?

And someone right at the back called out Twenty-eight!