Mine distinguish between dogs as well. From what I have seen hens also give such complex calls but they are not intended for being heard over long distances like those produced by roosters. What is really cool in how chicks respond to hen's warning about red-shouldered hawk versus red-tailed hawk. When red-shouldered chicks simply stop what they are doing and look up at hawk. When red-tailed hawk the chicks put on after-burners and sprint to heavy vegetation and hen stays back in open and raises a major ruckus apparently to distract hawk.My roosters used to have two different sounds they made for my two different dogs approaching. One dog ignored the birds and was very business-like and the roosters just gave the girls a "heads-up". The other dog had chased birds when a puppy and still got excited by the birds, and the roosters would give a more urgent call to gather the hens up a little when he approached.
I love good roosters. I've got one now who is just delighted at having four new chicks in his coop, cause he has more to give treats/food to!