INTRODUCTION. 



Amongst technical ornithologists it has been a custom, much to be 

 deplored, to describe all birds in which the sexes do not exhibit 

 marked differences in colour of plumage, or well-defined external 

 ornamentation, as follows : — " Female similar to male ; " but happily, 

 in the recent work done in the United States, where the most careful 

 measurements of every part of each individual of a species are being 

 l'ecorded, and where considerable trouble is taken to ascertain the 

 sex of preserved skins, the more or less constant differences which 

 presumably exist between the sexes of all birds are beginning to be 

 made apparent. 



To anyone who has for many years had his eyes trained to 

 appreciate slight differences of outline and colouring, characters 

 unnoticed by the more superficial observer are at once evident ; he 

 looks at his birds almost with the microscopic recognition of features 

 observable by themselves ; and thus is in a position not only to 

 distinguish the sexes, but to point out to others the peculiarities by 

 which they may be identified : that this cannot be done in every 

 case, is only evidence that even the trained eyesight of man is not 

 perfect enough to discover at once all those details which one would 

 suppose must be patent to a bird when seeking its mate ; nevertheless 

 it is conceivable that no external distinctions may exist, in a few 

 rare cases, and that in such instances a difference of scent, or tone 

 of voice, may be the guide. 



The object of the present work is to enable owners of birds to 

 decide to what sex they belong, and I hope that the labour which I 

 have expended upon the study of external sexual differences, embodied 

 in the ensuing chapters, will prove useful not only to the student of 

 birds in captivity, but of cabinet specimens : primarily, I naturally 

 offer it as a sort of vade mecum for the use of aviculturists, and 

 should it only be of assistance to them, I shall feel amply repaid for 

 the time and trouble which I have expended in its production. 



