Geraint Evans gave what he called a short talk on bird carving but it was encyclopedic in it's breadth and scope. He started with a brief history of bird carving starting with decoy ducks and going through the various fashions that have been in vogue.   We then heard about the research needed to get a bird right.   The eye sight of birds is to the side and backwards - monocular in colour, and to the front binocular but in black and white.   The shape of the bill / beak is controlled in part by the necessity of not interupting the bird's ability to see with it's binocular vison.    There were lots of details that came from books, magazines, specimens, and direct observation from life.    He said that birdwatchers are not a good source of information as the tend only to know enough to identify the species and not the anatomical details.  
The work involved in carving a bird was prodigious.    There were several operations requiring minute control that needed to be repeated upto eight times.    Because of the precise nature of the final result any error along the way would be obvious to the knowledgable and especially to competition judges.