I remember this story, that is sort of Sci-Fi/Fantasy, since it has talking chickens.
The chickens in this story are unique since they can fly (The talking part is apparently not worthy of notice) and they need to defend against marauding foxes.
They learn they cannot rely on the farmer and so train themselves. They eat more grit to grow harder shells. They sit in a hot shed, to try and boil the eggs internally, so that they can fly and dive bomb a fox with a hard boiled, hard shelled egg.
I have been driving my son crazy with Chicken references and need to track this story down to show him why it is I am so crazy.