This is a general idea of their height:
The adult male is 29–34 cm (11–13 in) long, with a wingspan of 59–64 cm (23–25 in) and a mass of 110–196 g (3.9–6.9 oz).The female is much larger at 35–41 cm (14–16 in) long, with a wingspan of 67–80 cm (26–31 in), and a mass of 185–342 g (6.5–12.1 oz). Females are usually 25% larger.
The Sparrow Hawk is the smallest and the handsomest American hawk. Most of them migrate southward in the fall but a few remain here all winter. The sparrow hawk, the pigeon hawk, the duck hawk and the gyrfalcons all belong to the falcon family, distinguished by their long pointed wings and streamlined shape. In the falcons, also, the upper bill of the beak has a tooth-like projection near the sharply-hooked tip, with a corresponding notch in the lower bill. Other than the sparrow hawk, only the much larger and broader-winged marsh hawk has markings on the male distinctively different from those of the female. The male sparrow hawk has ashy-blue wing coverts, chestnut tail with one black band near the end, and white underparts dotted with black spots. The female has chestnut wing coverts barred with black, several bars on her chestnut tail, and white underparts streaked with black. The heads of both are ashy-blue on top and white
on the sides and throat, with a conspicuous black vertical mark before the eye and another behind the eye.
The sparrow hawk seldom soars at great height. It is more apt to sail back and forth over a meadow, rather low, making a few quick exaggerated wing-strokes at intervals, hunting insects and mice. When they can get what they like, their diet is more than 50% grasshoppers and other insects, about 25% mice, perhaps 10% small birds, and the remainder spiders, frogs and small snakes. Fortunately, all hawks, and all owls except the great horned owl, are protected in Illinois and may not be killed.
The sparrow hawk usually nests in old woodpecker holes but sometimes in barns, factories or church steeples. Its call is a high-pitched metallic hysterical chatter remarkably like the warning note of the ground squirrel. Quickly repeated, it sounds something like "killy - killy - killy - killy".
It should be called the Grasshopper Hawk.