What is the qualification for designation as Hawk-Eagle ?

Taxonomy of the Changeable Hawk Eagle

There are also Ornate, Mountain and African Hawk Eagles.

http://en.wikipedia.org/wiki/Ornate_Hawk-Eagle

http://en.wikipedia.org/wiki/Mountain_Hawk-Eagle

http://en.wikipedia.org/wiki/African_Hawk-Eagle

There is a variety of eagles called hawk-eagles. These links discuss the specific birds and their characteristic, but I can’t find a reference that identifies why a bird is designated a hawk-eagle vs an eagle.

Nomenclature is lost in the mists of time. Folksy observations?

They are all raptors aka birds of prey.

The Merlin is known colloquially as a pigeon hawk.

The American Kestrel is also called a sparrow hawk.

It’s a confusing subject. Look at the species, subspecies and genus labels of these more- than-60 eagles.

http://en.wikipedia.org/wiki/Eagle