Probably no branch of aviculture has progressed so rapidly during the past twenty-five years as that which has for its central interest the production of the many beautiful and rare crosses between various species of birds which to-day tempt the appetite of the bird fancying public, ever on the look-out for something new. Besides their scientific interest (which is very considerable, insomuch that they show to a nicety in very many cases the exact degree of relationship which certain speci...