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.”
The average size of the eggs of this bird is 1.56 by 1.94 inches. The color is usually a uniform dull white, but is occasionally tinged with as light bluish shade. They are nearly spherical, though not more so than the eggs of several species, and are equal at either end. Their surface is slightly granulated. The number of the eggs varies from three to four, though occasionally there are five in a nest.
The maximum length of the egg of this species is 2.00 inches, the minimum 1.85; the maximum breadth 1.60, the minimum 1.50 inches. In occasional instances I have known the eggs of this species more or less distinctly marked, especially about the larger end, with blotches of a light yellowish-brown. Those most distinctly marked in this manner were taken and identified by Mr. Paine.
A nest of this Hawk, found by Dr. J. W. Velie, was built on a poplar-tree, about forty feet from the ground, and was composed of sticks and lined with moss and leaves. There was a small cleared space of three or four rods in extent, in the middle of which the tree stood, and about a quarter of a mile from the main channel of the Mississippi River, on Rock Island.
The Cooper Hawk was found on Mount Tom by Mr. William Street, nesting for the most part in pine or hemlock trees, usually choosing one in a thick clump. They begin to lay about the first of May, usually depositing four eggs. They are very shy, and it is almost impossible to get within shot of them, even when they have young. They rarely molest the poultry-yard, but seem to live chiefly on small birds and animals. They leave their nest at once whenever it is approached, and will not return until the intruder has gone.
The var. mexicanus, originally described by Mr. Swainson from Mexican specimens obtained near Real del Monte, has been ascertained to cross our boundaries, and is found in all the territory between the Rocky Mountains and the Pacific, as far north as Washington Territory. Dr. Cooper has never met with this Hawk, but supposes its general habits, and especially those regulating its migrations, closely resemble those of A. cooperi, to which the bird itself, in all but size, is so similar. Dr. Coues speaks of it as a common resident species in Arizona. He states that he has seen young birds of this species, reared by the hand from the nest, become so thoroughly domesticated as to come to their master on being whistled for, and perch on his shoulder, or follow him when shooting small birds for their food. They were allowed their entire liberty. Their ordinary note was a shrill and harsh scream. A low, plaintive, lisping whistle was indicative of hunger.