Bird form bodies are selected by length and circumference (girth).
After skinning, measure the circumference at the largest portion of the body with a tape measure (C).
The use of calipers to measure the bird body length will help you avoid the errors inherent in measuring body length with a ruler.
To measure length (L), place one end of the calipers at the base of the tail and the other at the front of the breast as illustrated. The caliper measurement is then read from a ruler.
Select the right bird form using these length and circumference figures.