This has got to be the most exhaustive gathering of material on Avian Hybrids I have ever seen! Having been working with small birds, quail,pigeons, parrots and doves for over 45 years, I wish I would have had something like this years ago. Once you realize that the code to understanding the book is in the front pages you can easily understand which birds hybridize in fertile or non fertile crosses. I am especially in to pesserines and Dr. McCarthy's list of Canary crosses is absolutely awesome! Some I had never considered and some I had experienced yet had been accused of lying. I knew I was not and he presents the truth that others have had the same results as I! That is so cool! I would recommend that any one who is into hybridizing any kind of bird, from ducks, to canaries, turkeys to black birds, you have got your listing here and this will save you years and years of work. Yours in the sport: D. David E. Cummings--Kanaryman Aviaries and Research Foundation