This story was referenced in a TFS seminar today.
Here is an easy definition of the Chickens versus Pigs.
A Pig is someone who has skin in the game. Pig roles are considered core team members.
A Chicken is someone who has something to gain by the Pigs performing, but in the end, really do not contribute day to day to “getting things done.” Their “eggs” are a renewable resource, and numerous.
Read more at The Classic Story of the Pig and Chicken.