The successive stages of development of the colours and plumage of the Birds of Paradise are very interesting, from the striking manner in which they accord with the theory of their having been produced by the simple action of variation, and the cumulative power of selection by the females, of those male birds which were more than usually ornamental. Variations of _colour_ are of all others the most frequent and the most striking, and are most easily modified and accumulated by man's selection of them. We should expect, therefore, that the sexual differences of _colour_ would be those most early accumulated and fixed, and would therefore appear soonest in the young birds; and this is exactly what occurs in the Paradise Birds. Of all variations in the _form_ of birds' feathers, none are so frequent as those in the head and tail. These occur more, or less in every family of birds, and are easily produced in many domesticated varieties, while unusual developments of the feathers of the body are rare in the whole class of birds, and have seldom or never occurred in domesticated species. In accordance with these facts, we find the scale-formed plumes of the throat, the crests of the head, and the long cirrhi of the tail, all fully developed before the plumes which spring from the side of the body begin to mane their appearance. If, on the other hand, the male Paradise Birds have not acquired their distinctive plumage by successive variations, but have been as they are mow from the moment they first appeared upon the earth, this succession becomes at the least unintelligible to us, for we can see no reason why the changes should not take place simultaneously, or in a reverse order to that in which they actually occur.
What is known of the habits of this bird, and the way in which it is captured by the natives, have already been described at page 362.
The Red Bird of Paradise offers a remarkable case of restricted range, being entirely confined to the small island of Waigiou, off the north-west extremity of New Guinea, where it replaces the allied species found in the other islands.
The three birds just described form a well-marked group, agreeing in every point of general structure, in their comparatively large size, the brown colour of their bodies, wings, and tail, and in the peculiar character of the ornamental plumage which distinguishes the male bird. The group ranges nearly over the whole area inhabited by the family of the Paradiseidae, but each of the species has its own limited region, and is never found in the same district with either of its close allies. To these three birds properly belongs the generic title Paradisea, or true Paradise Bird.