The term hawk refers to birds of prey in any of three senses:
Strictly, to mean any of the species in the generaAccipiter, Micronisus, Melierax, Urotriorchis, and Megatriorchis. The widespread Accipiter genus includes goshawks, sparrowhawks, the Sharp-shinned Hawk and others. They are mainly woodland birds that hunt by sudden dashes from a concealed perch. They usually have long tails and high visual acuity.
The common names of birds in various parts of the world often use hawk loosely. For example, in North America, the buzzards (Buteo) are often called "hawks".
The true hawks form the family Accipitrinae and most are in the genus Accipiter
Tarsus, tibia coracoid and humerus were compared in detail, with the result that my first impression was greatly strengthened and I came to agree pretty closely with Peters' arrangement.
He recognizes nine subfamilies of the Accipitridae which he lists seriatim with Accipitrinae as no. 4.
The genus Harpagus is assigned to subfamily no. 3, the Milvinae, including the old world type, Milvus milvus milvus.