Look at the bottoms of their feet. If the bottoms of the feet are an obvious yellow, it is a Black Jersey Giant. If the bottoms of the feet are any other color (whitish, grayish, pinkish), it is a Black Australorp.Hi Michael OShay. Last year we purchased the Black Jersey Giants and the Black Australorps at the same time. We could tell them apart until they fully feathered out. Now, we can't. They all look the same. My husband said that they are probably all the same breed. Do you know how to tell them apart? They are all around the same size.