Dr. Hoy, in a communication to the Boston Natural History Society, mentions finding four nests of this Hawk in a single season, and his careful observations of the habits of the parent birds enabled him to ascertain that in each instance the birds began to sit constantly upon their nest as soon as a single egg had been deposited, and that, as a consequence, the eggs having been deposited at varying intervals, each one was found in a different stage of incubation from the other. In not a single instance did he visit a nest without finding the parent bird occupying it. These nests were all composed of sticks, rudely lined with strips of bark and a few bunches of _Usnea barbata_. The nests were quite shallow and small for a Hawk. Most of the eggs were sparingly sprinkled with umber-brown. One set of these eggs was blotched with bluish-green, which soon faded out. While the nests were being molested, the parent Hawk would fly from tree to tree, uttering, in rapid succession, _quick-quick-quick-quick_. Dr. Hoy states that the male of this species, during the nesting-season, may frequently be seen flying high in the air, sporting, vaulting, and turning somersaults on the wing, which habit has given to it the name of Tumbler-Hawk. No Hawk is harder to shoot, and none commits greater havoc among barn-yard fowls than this species. He has seen one strike a large hen while she was flying wildly for safety, and kill her on the spot, though it was obliged to abandon the game, as it proved too heavy to carry off. I have specimens of its eggs from South Carolina, obtained by the young sons of Rev. M. A. Curtis, of Society Hill. Mr. Curtis, Sen., furnished me with the following description of its nest: “The nest of the Cooper’s Hawk was built in the triple fork of a tall black gum (_Nyssa multiflora_), near the top of the tree, which stood in a swamp. It was formed of a layer of small sticks, ⅓ to ½ inch in diameter. Its external diameter varied from 1½ to 2 feet. This layer was ⅞ of an inch in thickness, with only a slight depression in the centre, hardly enough to keep the eggs from rolling out. A few thin pieces of pine bark formed the bed for the eggs.” Another nest, obtained in Randolph, Vt., by Charles S. Paine, Esq., is thus described by him: “The nest was built of hemlock twigs, and lined with small, thin pieces of hemlock bark, such as hang loosely on the tree. The Hawk, when the nest was approached, did not whistle, as some others of that family do, but uttered a cry of _ge! ge! ge! ge!_ This was repeated several times, with great rapidity, by both male and female.”