These birds feed on frogs, insects, worms, young alligators, carrion, and various other forms of animal food. Mr. Audubon states that he has seen them walk about in the water in search of food, catching frogs, young alligators, etc. It is harmless and inoffensive, and in the destruction of vermin renders valuable services. It builds a coarse, flat nest, composed of flags, reeds, and grass, usually on the tops of trees, but occasionally, according to Darwin, on a low cliff, or even on a bush.

Mr. R. Owen, who found this bird breeding near San Geronimo, Guatemala, April 2 (Ibis, 1861, p. 67), states that the nest was built on the very crown of a high tree in the plain. It was made of small branches twisted together, and had a slight lining of coarse grass. It was shallow, and formed a mass of considerable size. The eggs were four in number, and are described as measuring 2.15 inches by 1.60, having a light red ground-color, and spotted and blotched all over with several shades of a darker red.

Dr. Heermann found the nest of this species on the Medina River. It was built in an oak, and constructed of coarse twigs and lined with leaves and roots. It was quite recently finished, and contained no eggs. Mr. Dresser states that it breeds all over the country about San Antonio, building a large bulky nest of sticks, lined with small roots and grass, generally placed in a low mesquite or oak tree, and laying three or four roundish eggs, similar to those of the Honey Buzzard of Europe. He found several nests in April and through May, and was told by the rancheros that its eggs are found as late as June. The nests found in the collection of Dr. Berlandier, of Matamoras, were coarse flat structures, composed of flags, reeds, and grass. The nests, though usually built on the tops of trees, are occasionally found, according to Darwin, on a low cliff, or even on a bush. The number of the eggs is rarely, if ever, more than three or four. Four eggs, taken by Dr. Berlandier near the Rio Grande, exhibit a maximum length of 2.44 inches; least length, 2.25; average, 2.41. The diameter of the smallest egg is 1.75 inches; that of the largest, 1.88; average, 1.81. These eggs not only present the great and unusual variation in their length of nearly eight per cent, but very striking and anomalous deviations from uniformity are also noticeable in their ground-color and markings. The ground-color varies from a nearly pure white to a very deep russet or tan-color, and the markings, though all of sepia-brown, differ greatly in their shades. In some, the ground-color is nearly pure white with a slight pinkish tinge, nearly unspotted at the smaller end, and only marked by a few light blotches of a sepia-brown. These markings increase both in size and frequency, and become of a deeper shade, as they are nearer the larger end, until they become almost black, and around this extremity they form a large confluent ring of blotches and dashes of a dark sepia. Others have a ground-color of light russet, or rather white with a very slight wash of russet, and are marked over the entire surface, in about equal proportion, with irregular lines and broad dashes of dark sepia. Again, in others the ground is of the deepest russet or tan-color, and is marked with deep blotches of a dark sepia, almost black. The eggs are much more oblong than those of most birds of prey, and in this respect also show their relation to the Vultures, rather than to the Hawks or Eagles. They are pyriform, the smaller end tapers quite abruptly, and varies much more, in its proportions, from the larger extremity, than the eggs of most true Hawks.

Lieutenant Gilliss found the South American race exceedingly numerous throughout Central and Southern Chile. It was constantly met with along the roads, and wherever there was a chance of obtaining a particle of flesh or offal. At the annual slaughtering of cattle they congregate by hundreds, and remain without the corral, awaiting their share of the rejected parts. It was so tame, from not being molested, that it could be taken with the lasso, but when thus captured, it fights desperately, and no amount of attention or kindness can reconcile it to the loss of liberty.

Throughout South America it is one of the most abundant species, its geographical range extending even to Cape Horn. Mr. Darwin found the Polyborus nowhere so common as on the grassy savannas of the La Plata, and says that it is also found on the most desert plains of Patagonia, even to the rocky and barren shores of the Pacific.

Genus PANDION, Savigny.

Gen. Char. Bill inflated, the cere depressed below the arched culmen; end of bill much developed, forming a strong, pendent hook. Anterior edge of nostril touching edge of the cere. Whole of tarsus and toes (except terminal joint) covered with rough, somewhat imbricated, projecting scales. Outer toe versatile; all the claws of equal length. In their shape, also, they are peculiar; they contract in thickness to their lower side, where they are much narrower than on top, as well as perfectly smooth and rounded; the middle claw has the usual sharp lateral ridge, but it is not very distinct. All the toes perfectly free. Tibiæ not plumed, but covered compactly with short feathers, these reaching down the front of the tarsus below the knee, and terminating in an angle. Primary coverts hard, stiff, and acuminate, almost as much so as the quills themselves; third quill longest; first longer than fifth; second, third, and fourth sinuated on outer webs; outer three deeply emarginated, the fourth sinuated, on inner webs.

Of this remarkable genus, there appears to be but a single species, which is almost completely cosmopolitan in its habitat. As in the case of the Peregrine Falcon and Barn Owl, different geographical regions have each a peculiar race, modified by some climatic or local influence. These races, however, are not well marked, and are consequently only definable with great difficulty.