Breed Differences

Really, the only similarity is that they are all black. They all have a different body shape (esp. the minorcas compared to the other two) and different feathering. They also all lay different colored eggs. Marans lay (or at least should) a dark brown egg, australorps lay your standard light brown/tan colored egg, and minorcas are white egg layers.

 

Two good ones are... ithaca.edu and look for Hendersons Handy-Dandy Chicken Chart. Also, avian web.com

 

A good visual key is that Black Marans have feathered legs and are quite rare, Black Australorps are just plain black chickens and VERY common, and Black Minorcas have an unmistakable large white earlobe, plus they're also very rare.