Harlequin Quail (_Coturnix delegorguei_) 124
_By permission of the Avicultural Society._
Rain Quail (_Coturnix coromandelica_) 124
The markings on the throats of these quails are of the type usually put down as “recognition marks,” but as the Harlequin Quail is African and the Rain Quail Indian, the two species cannot possibly interbreed. The pattern, then, can have no “recognition” significance. _By permission of the Avicultural Society._
Like most of the group to which it belongs, this honey-eater (_Tropidorhynchus bouruensis_) is a soberly coloured bird, but is noisy, active, and aggressive. _By permission of Messrs Hutchinson & Co._
This “mimicking” oriole (_Oriolus bouruensis_) is of the same tone of colour as its supposed model the Friar-bird of the same island. _By permission of Messrs Hutchinson & Co._
This very conspicuous black bird (_Dicrurus ater_), ranging from Africa to China, is a striking feature of the landscape wherever it occurs. _By permission of Messrs Hutchinson & Co._
The fork of the tail in this bird is unique among cuckoos, but is nevertheless much less developed than in the supposed model, and may be an adaptation for evolutions in flight, as such tails usually appear to be. _By permission of Messrs Hutchinson & Co._
The upper surface of the tail, not shown in this drawing, exactly corresponds with that of the cuckoo “mimic.” _By permission of Messrs Hutchinson & Co._
This species (_Hierococcyx varius_) is commonly known in India as the “Brain-fever bird.” _By permission of Messrs Hutchinson & Co._
This species (_Icterus vulgaris_) is that most frequently seen in captivity; the pattern of colour is found in several other allied forms. _By permission of Messrs Hutchinson & Co._
Several other orioles besides this (_O. melanocephalus_) have the black head. _By permission of Messrs Hutchinson & Co._
This species (_Tetraenura regia_) is a typical example of seasonal sexual dimorphism, the male being long-tailed and conspicuously coloured only during the breeding season, and at other times resembling the sparrow-like female. _By permission of the Foreign Bird Club._
Illustrating display by a species with no decorative colouring or sex difference.
CHAPTER I RISE OF THE THEORY OF NATURAL SELECTION AND ITS SUBSEQUENT DEVELOPMENT