Accipitrinae
The Accipitrinae are the subfamily of the Accipitridae often known as the "true" hawks, including all members of "Accipiter" and the closely related genera "Melierax", "Urotriorchis", "Erythrotriorchis" and "Megatriorchis". The large and widespread genus "Accipiter" includes goshawks, sparrowhawks, the sharp-shinned hawk and others. They are primarily woodland birds that hunt by sudden dashes from a concealed perch, with long tails, broad wings and high visual acuity facilitating this lifestyle. In light of recent genetic research, the kites of the traditional subfamily Milvinae may also belong to this group. Hawks, including the accipitrines, are believed to have vision several  times sharper than humans, in part because of the great number of photoreceptor cells in their retinas (up to 1,000,000 per square mm, against 200,000 for humans), a very high number of nerves connecting the receptors to the brain, and an indented fovea, which magnifies the central portion of the visual field. Hawks and humans. Hawks are sometimes used in falconry, a sport in which trained birds of prey are flown at small game for sport.