Mattie Sue Athan is one of the world’s most experienced parrot behavior consultants. 
In business since 1978, her work is famous for being logical, understandable, practical. 
Mattie Sue has a special interest in the influence of environment on parrot behavior. 
Her books are industry standards: 

GUIDE TO A WELL-BEHAVED PARROT, 
GUIDE TO COMPANION PARROT BEHAVIOR, and 
GUIDE TO THE QUAKER PARROT. 
She coauthored THE AFRICAN GREY PARROT HANDBOOK 
and GUIDE TO THE SENEGAL PARROT AND ITS FAMILY, with Dianalee Deter. 

There’s a book on secondhand parrots in progress.