As an example of sexual dimorphism, the male Mockery Birds have a large hump on their beak, while the females have only a small, bony shield. The bird was named after its call, that sounds like laughter (much like the kookaburra's).
The fictitious bird species of the book, the Mockery Bird is a flightless bird about the size of a goose. It has blue feathers, long legs and a large beak, similar to that of a hornbill.