The animal on the cover of Natural Language Annotation for Machine Learning is the cockatiel (Nymphicus hollandicus). Their scientific name came about from European travelers who found the birds so beautiful, they named them for mythical nymphs. Hollandicus refers to “New Holland,” an older name for Australia, the continent to which these birds are native. In the wild, cockatiels can be found in arid habitats like brushland or the outback, yet they remain close to water. They are usually seen in pairs, though flocks will congregate around a single body of water.

Until six to nine months after hatching, female and male cockatiels are indistinguishable, as both have horizontal yellow stripes on the surface of their tail feathers and a dull orange patch on each cheek. When molting begins, males lose some white or yellow feathers and gain brighter yellow feathers. In addition, the orange patches on the face become much more prominent. The lifespan of a cockatiel in captivity is typically 15–20 years, but they generally live between 10–30 years in the wild.

The cockatiel was considered either a parrot or a cockatoo for some time, as scientists and biologists hotly debated which bird it actually was. It is now classified as part of the cockatoo family because they both have the same biological features—namely, upright crests, gallbladders, and powder down (a special type of feather where the tips of barbules disintegrate, forming a fine dust among the feathers).

The cover image ...

Get Natural Language Annotation for Machine Learning now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.