There are quite a few pure breeds that are mostly or all black (examples: Black Australorp and Black Minorca)
There are also types of chickens that are created by crossing other breeds, and that can be black. Easter Eggers (lay blue or green eggs) can be black, and Olive Eggers (lay darker green eggs) are often black, because of what breeds are commonly crossed to produce them.
Knowing what color eggs a chicken lays can help figure out the breed-but not if it's male!
Upon a bit of research, I believe that the Bomgaar's breed list for ordering is consistent with Hoover Hatchery's, so that's where they're likely from. Looking at what they consider rare breeds, it's likely a Black Orpington or a Black Andalusian (only blue are listed, but when breeding two blue breeds together, 25% come out black). You'll be able to tell by earlobe color and body type very easily