Mr. Audubon states that the flight of this species is never protracted. It seldom flies far at a time; a few hundred yards are all the distance it usually goes before alighting. It rarely sails long on the wing at a time; a half-hour is its utmost extent. In pursuing a bird, it flies with great rapidity, but never with the speed of the Sharp-shinned and other Hawks. Its cry is so similar to that of the Kestrel of Europe that it might be readily mistaken for it but for its stronger intonation. At times it gives out these notes as it perches, but they are principally uttered while on the wing. Mr. Audubon has heard them imitate the feeble cries of their offspring, when these have left the nest and are following their parents.

The young birds, when they first appear, are covered with a white down. They grow with great rapidity, and are soon able to leave their nest, and are well provided for by their parents until they are able to take care of themselves. They feed at first on grasshoppers and crickets.

At Denysville, Me., these Hawks were observed to attack the Cliff Swallows, while sitting on their eggs, deliberately tearing open their covered nests, and seizing their occupants for their prey.

In winter, these birds, for the most part, desert the Northern and Middle States, but are resident south of Virginia. They can be readily tamed, especially when reared from the nest. Mr Audubon raised a young Hawk of this species, which continued to keep about the house, and even to fly to it for shelter when attacked by some of its wilder kindred, and never failed to return at night to roost on its favorite window-shutter. It was finally killed by an enraged hen, whose chickens it attempted to seize.

This Hawk constructs no nest, but makes use of hollow trees, the deserted hole of a Woodpecker, or even an old Crow’s nest. Its eggs are usually as many as five in number, and Mr. Audubon once even met with seven in a single nest. The ground of the eggs is usually a dark cream-color or a light buff. In their markings they vary considerably. Five from a nest in Maryland were covered throughout the entire surface with small blotches and dottings of a light brown, at times confluent, and, except in a single instance, not more frequent at the larger end than the smaller. The contents of a nest obtained by Mr. Audubon on the Yellowstone River had a ground-color of a light buff, nearly unspotted, except at the larger end, with only a few large blotches and splashes of a deep chocolate. In others, interspersed with the light-brown markings are a few of a much deeper shade. In some, the eggs are covered with fine markings of buff, nearly uniform in size and color; and others again are marked with lines and bolder dashes of brown, of a distinctly reddish shade, over their entire surface, and often so thickly as nearly to conceal the ground. The eggs are nearly spherical. The average length is 1.38 inches by a breadth of 1.13. They are subject to variation in size, but are uniform as to shape. They range in length from 1.48 to 1.32 inches, and in breadth from 1.08 to 1.20 inches.

The eggs of Tinnunculus sparveroides, from Cuba, and of var. cinnamominus from Chile, differ in size and markings from those of North American birds. Their ground-color is much whiter, is freer from markings which have hardly any tinge of rufous, but are more of a yellowish-brown. The Cuban egg measures 1.28 by 1.08 inches; the Chilian, 1.25 by 1.08.

Genus POLYBORUS, Vieillot.