As to the question whether certain combinations of characters occur with special frequency, the evidence is insufficient to give a definite answer. Among all the birds I have seen in America or in England I have not yet found one having the malar patches black without any nuchal crescent. Of Dr. Bishop's 8 adults not one, however, showed the combination of the three chief features normal for _auratus_ or for _cafer_. Besides the two forms that we have hitherto considered, several other local types exist, and these throw some further light on the problem. Of these the most important in this connexion is _chrysoides_, which inhabits the whole of southern California and the mainland opposite. This remarkable form is as Allen says, very different from _auratus_ except that it has the quills yellow like _auratus_, not red like _cafer_. So that we find here in the extreme west of the whole distribution a type agreeing in one of its chief features with the eastern type. Between this and _cafer_ intergrades have, according to Allen, not been found. The relations of this _chrysoides_ are, Allen thinks, rather with _mexicanoides_, a southern, smaller race with colours more intense, which inhabits Guatemala, but however that may be, it must be regarded as a _cafer_ which has lost its red quills. The island of Guadeloupe off Lower California has an island form. Beyond the other side of the continent there is also an island form of _auratus_, inhabiting Cuba, so that clearly the yellow quills can extend into the tropics. The above account is in many respects incomplete, but it suffices to give an outline of the chief facts. The whole problem is complicated by the undoubted effects of an uncertain amount of migration, and in many, perhaps all, districts, the winter population differs from the summer population of the same localities. The existence of these seasonal ebbs and flows is now well known to ornithologists, and most of the bird species of temperate regions are subject to them.