Coloration, which varies relatively rapidly in response to differing ecological conditions, has become more different in the species of Bombycillidae than is true in many other families of passerine birds. The explanation lies in early geographical isolation of the three subfamilies, with consequent radiation in three directions. Waxwings have become adapted by possessing a thick protective layer of feathers and drab coloration broken by ruptive marks. They still retain the streaked plumage, which is probably ancestral, in the juveniles; this is lost at the first molt in the fall. In its evolution, _Dulus_ has developed large feet, heavy decurved beak, and the large communal nest that affords protection from enemies; as a consequence, perhaps _Dulus_ did not need a plumage different from the primitive and streaked one. The survival of _Dulus_ may not have depended on either ruptive marks or on brilliant and outstanding plumage. The large feet and large bill seem to be responses to particular ecological requirements, as will be shown later. The Ptilogonatinae, with habits paralleling those of the flycatchers, probably are considerably modified from the ancestral stock; the coloration probably is more brilliant and conspicuous. Perhaps this type of coloration and the habit of capturing insects from a perch are correlated. Some amount of territoriality is characteristic of this subfamily and dimorphism in color--the plumage of the male is outstandingly conspicuous--possibly is of selective value to the race. In a tropical forest community, a duller pattern possibly would be more visible and thus would be selectively disadvantageous. COURTSHIP Waxwings are gregarious birds and individuals establish no well-defined territories as do many birds. The nest itself is the only defended territory, and as Crouch (1936) has shown, the Cedar Waxwing will nest in close proximity to others of the same species. Swarth (1932:275) mentions that the Bohemian Waxwing is tolerant of the nests of other pairs near by. The extreme condition is that found in _Dulus_, in which the territory is not limited even to the nest, but to the individual compartment of the community nest. _Phainopepla_, a less gregarious bird than _Dulus_ and waxwings, has a much more definite territory, although individuals of _Phainopepla_ are tolerant of others of the same species; no feeding territory is established, and small flocks of birds feed together at any time of the year.