There has been a great deal of discussion as to the proper systematic position of the Ospreys ( Pandion), and even now their status can hardly be regarded as definitely settled. From the fact that they possess a more or less reversible outer toe, and also certain peculiarities in the skeleton, they were long held to exhibit a more or less distinct transition between the diurnal birds of prey and the Owls; but since it has been conclusively shown that the latter have little or nothing in common with the former, and have been removed to the midst of the so-called “Picarian” birds, a further examination of the various characters of the Ospreys has been necessary. According to Pycraft the outer toe is not more reversible than in ordinary Accipitres, and, all things considered, it seems likely that they find their closest relatives among the Honey Buzzards and their allies, being by some authorities, indeed, placed in the subfamily Pernince, but it is perhaps best to regard them as constituting by themselves a distinct subfamily (Pandionince).
Ospreys, or Fish Hawks, as they are more commonly called in this country, enjoy an almost cosmopolitan distribution, being absent only from southern South America, New Zealand, Iceland, and some parts of Australia. They are so well known that an extended description is perhaps unnecessary, yet a few of the more important characters may be mentioned. When perching, the toes are disposed as in ordinary diurnal birds of prey, but when they capture a fish the toes are opposed in pairs, the outer toe being, as above pointed out, quite reversible. This reversibility permits of a very secure hold on their prey, which is usually an advantage, although, as will be shown later, the very security of the hold works occasionally to their detriment. The feet are large and powerful, the toes being Unconnected and provided with very large, strongly curved claws, which are of equal length, and narrowed and rounded on the under sides. The whole of the rather short tarsus and the toes are covered with rough, somewhat imbricated, projecting scales, and the under surface of the toes is covered with quite prominent pointed spicules, an adaptive character, found also in other piscivorous Accipitres, as for example the genus Busarellus. The plumage, while close and compact, is without aftershafts, thus agreeing with the Owls. The bill is inflated, the cere depressed, and the nostrils not concealed by bristles. They have long, pointed wings in which the coverts as well as the primaries are very hard and stiff. In color the Ospreys are dark brown or grayish brown above and mainly pure white below, with slight variations in the various races. The length is from twenty-two to twenty-five inches and the spread of wings about five feet.
Some three or four species of Ospreys have been described, but it is now generally recognized that there is but a single species, which in different parts of its range has assumed sufficient differences in size and plumage to warrant being separated as more or less well marked subspecies. The principal or central form is the European Osprey ( Pandion haliaëtus haliaëtus), which is found throughout the Eastern Hemisphere and has the breast always spotted with brownish. The next in importance is the American Osprey (P. h. carolinensis), found throughout temperate and tropical America in general, except in the Bahamas, where there is a local race sometimes recognized as the Bahama Os-prey (P. h. ridgwayi). The first has the breast usually entirely without spots, while the latter is a smaller form with the back paler than in the American Osprey, and the bill much larger and more swollen. The smallest of all is the Australian Osprey (P. h. leucocephalus) of Australia and the Indo-Malayan islands.
Habits. Inasmuch as the habits of the Ospreys are much the same wherever found, the following account will largely be that of the American form, which is a familiar bird to those who dwell near the ocean or large inland bodies of water. In the more northern part of its range the Fish-Hawk is migratory, coming in the early spring as the first harbinger of the breaking up of winter, the males preceding the females by several days. They spend the winter mainly in the Southern States, greatly augmenting, at that time, the number that remain there the year around. These birds are much attached to their homes and return year after year to the same nest, where if unmolested they rear an annual brood. Like certain other birds of prey they are supposed to mate for life, and many are the stories told of their devotion to each other. One particular incident may be cited. A pair of Fish-Hawks had their nest in a tall locust tree. “At a time when one of the birds, presumably the female, was on the nest, a bolt of lightning struck the tree, killing the bird and demolishing the nest. Strangely enough, the other Osprey, when returning only to find his home desolated, took up his station upon the top of one of the uninjured trees close at hand, and throughout the remainder of the summer, was seen day after day, month after month, keeping his lonely vigil, apparently mourning the loss of his mate. By those who lived in the vicinity it was asserted that he was never missing from his post; and many were the speculations indulged with regard to the manner of his subsistence. Some inclined to the opinion that he went fishing very early in the morning and so escaped observation; while others supposed him to have been fed by other Fish-Hawks who took pity on his lonely state.”
Fish-Hawks are very peacefully inclined birds. So tolerant are they at the presence of other birds that they permit Grackles and Night Herons to nest unmolested in the interstices of their great nests. They subsist almost entirely on fish, which they capture themselves, and only when hard pushed by hunger will they take dead fish. Occasionally they may kill another bird, and in some parts of their range, especially in the lower Mississippi Valley, they seem to be particularly fond of snakes. The kinds of fish taken are apparently of little moment to them, but they are principally those species which come near to the surface. Along the coasts they take shad, alewives, menhaden, and mullets, while in inland waters suckers, catfish, salmon, trout, and white perch form perhaps the chief items of diet. Their manner of fishing is rather peculiar, and quite different from that pursued by other fish-catching birds of prey, or even of fish-catching birds in general. One may be seen winging its way slowly over the water, keeping a keen watch for any fish that may be near the surface. ” When one is observed,” says Mr. Frank M. Chapman, ” it pauses, hovers a moment, and then, closing its wings, descends with a speed and directness of aim that generally insure success. It strikes the water with great force, making a loud splash, and frequently disappears for a moment before rising with its prey grasped in its powerful talons.” The manner of descent has been further described by Mr. Paul Bartsch, who says : ” The Osprey shifts its center of gravity when it passes above the water as does the Kingfisher, whose body changes almost to a vertical from the horizontal position as he prepares for a plunge. Neither does the Osprey dive head first as does the Kingfisher; but he plunges into the water with wings extended widely upward, clutching his prey with his powerful outstretched talons.” It has been known to strike the water with such force as to break a wing, and quite a number of cases are on record of their striking a fish too large for them to handle, and being unable to loosen their claws, have been drawn under and drowned. Curiously enough they always carry their prey head first, and if captured in another position they are said to turn it around in mid-air. As soon as they secure a fish they start for the land, and if not robbed of it by a watchful Eagle, resort to a particular spot, where it is devoured at leisure. Wherever food is perennially abundant the Fish-Hawks often occur in colonies of several hundred, but in other localities less favored only one or two pairs are found. I have seen a dozen nests within a short distance along the Yellowstone Lake, the birds apparently feeding on the trout so abundant there.
The nesting site selected by the Fish-Hawk is extremely varied, although usually it is a tall tree, especially one that has the top or a large limb broken out by a storm. In some localities, as for example Plum Island, New York, where the birds are protected, they build the nest on low trees, on chance piles of rails, or even on the ground. ” The most picturesque nesting site of the Osprey I ever saw,” says Bendire, ” was located in the midst of the American Falls of Snake River, Idaho. Right on the very brink of these, and about one third of the way across, the seething volume of water, confined here between frowning walls of basalt, was cleft in twain by a rocky obstruction which had so far withstood the ever eroding currents, and this was capped with a slender and fairly tapering column of rock rising directly out of the swirling and foaming whirlpool below. On the top of this natural monument, whose apex appeared to me to be scarcely two feet wide, a pair of Ospreys had placed their nest and were rearing their young amidst the never ceasing roar of the falls directly below them.” The nest is ordinarily composed of large sticks, brush, and rubbish of various kinds, such as cornstalks, seaweeds, etc., and lined with cedar bark and other finer material. At first it is of small size, but it is added to year after year, and finally assumes large dimensions, being sufficient in some cases to make several cart loads. The birds are brave in defense of the nest, flying at an intruder and uttering shrill screams. The number of eggs is usually two or three, rarely four, and they show great variety in both shape and color. Some-times they are white and unmarked, occasionally an almost solid chocolate, but mainly they are a buffy white more or less heavily marked with various shades of brown.