slim

I have a presumably leghorn or some sort of mix of it, rooster which is weaker and frailer than the other chickens his age. They're all about 4-5 months. I feed them chicken feed mixed with some cracked corn. It's not that he doesn't eat, infact he eats a lot. His crop gets full, like a ball...

What breed is my chicken? Also what is its gender? I think its a hen but could use confirmation. Its name is Crow. Its black with blue/purple feathers on the lower part of its wings. Its about 4 months old.