[Published in 1937: Smithsonian Institution United States National Museum Bulletin 167 (Part 1): 321-333]
On June 20, 1782, our forefathers adopted as our national emblem the bald eagle, or the "American eagle" as it was called, a fine looking bird, but one hardly worthy of the distinction. Its carrion-feeding habits, its timid and cowardly behavior, and its predatory attacks on the smaller and weaker osprey hardly inspire respect and certainly do not exemplify the best in American character. The golden eagle is a far nobler bird, but it is not strictly American. The wild turkey was suggested, but such a vain and pompous fowl would have been a worse choice. Eagles have always been looked upon as emblems of power and valor, so our national bird may still be admired by those who are not familiar with its habits. Its soaring flight, with its pure white head and tail glistening in the sunlight, is really inspiring; and it adds grandeur to the scene as it sits in a dignified pose on some dead tree, its white head clearly visible against the dark green of the forest background.
Courtship.--I find practically nothing in print on this subject, but C. J. Pennock says in his notes: "During late September and through October may be said to be their mating season in Florida. At this period they are to be seen flying over the marshes and open water, two or three in rapid chasing flights." They are probably mated for life, but if one of a pair is killed the survivor promptly secures a new mate, and occasionally the new mate is a bird in immature plumage. Almost always both birds of a breeding pair are white-headed adults.
I have seen an immature bird mated with an adult, and several other observers have reported it, but all seem to agree that it seldom occurs. I have never heard of a mated pair in which both birds were immature. Donald J. Nicholson, who has examined 125 eagles' nests, tells me that only once has he found an immature eagle mated with an adult.
Nesting.--My experience with the nesting habits of the bald eagle has been mainly in Florida, where this great bird is widely distributed, very common for a large bird, and so seldom disturbed by man that it nests, with confidence in its safety, often close to human habitations. I saw two occupied nests on golf courses, where players were passing daily almost under the nesting trees. And several nests were within sight of or even close to houses, or in open parks near much-traveled roads. During the winter of 1924-25, with the help of Oscar E. Baynard, we visited 18 eagles' nests in Pinellas County. These were located mainly near the shores of various bays or inlets, and all were in large longleaf pines, though two of the nesting trees were dead. The nests were placed 35 to 63 feet above the ground, about half of them being between 50 and 60 feet up. A typical nest was found on an island near Pass-a-grille on November 18, and the eagle flushed from the nest, but I did not climb to it until November 27, when it contained two eggs about one-quarter incubated. It was 40 feet up in a large pine in an open grove of longleaf pines; it rested on several branches and was made of large sticks and rubbish, with a lot of green and dry pine needles and Spanish moss in the flat top; in the center was a pretty little hollow, 20 inches in diameter and 4 or 5 inches deep, lined with the soft gray moss and small pine needles, in which the eggs were partially buried. It was a large nest, 7 feet high and 7 1/2 by 5 1/2 feet across the flat top. There was considerable white down scattered over the top of the nest. This pair of eagles laid a second set of eggs in the same nest later in the winter; I climbed to it on February 14 and found two eggs in it; I left them to hatch, as I wanted to photograph the young, but the eagles deserted the nest and the eggs never hatched.
I have seen three eagles' nests on the Florida Keys, the only nests I have ever seen in Florida that were not in pine trees. These were on the larger keys, where there was a heavy growth of large black mangroves, and the nests were in the main crotches of these trees at heights ranging from 30 to 40 feet; they were the usual large nests, 5 or 6 feet in height and about the same in diameter; one that I examined was lined with straw and grasses.
An interesting nest that I climbed to on November 26, 1911, near Mount Pleasant, S.C., was 45 feet up among the main branches of a longleaf pine; it was made of large pine sticks, cornstalks, sedges, and grasses and was deeply lined in the center, up to the level top, with soft grasses, Spanish moss, and feathers. No eggs were visible, but I found them deeply buried under fully 2 inches of the soft lining, completely concealed; the eggs had evidently been covered by the eagle when she left the nest.
J. R. Pemberton showed me a picturesque nest on Catalina Island, Calif., on February 22, 1929. The north end of the island terminates in a long, narrow cape, with steep, sloping sides leading up to a knife-edged, rocky ridge, 400 to 500 feet above the sea. On the top of a pinnacle of rock on the crest of this ridge was the eagle's nest. It was a laborious, but not a dangerous, climb to reach it, but it was well worth while. It was a shallow nest on the flat summit of the rock, about 6 feet long by 3 feet wide; it was made of dead sticks from the bushes that grew on the lower slopes and was profusely lined with grasses and decorated with a little white down. We found another old nest on San Nicholas Island, a great pile of sticks, 8 to10 feet high, on a little shelf on an overhanging cliff.
These eagles are still fairly common on some of the other Santa Barbara Islands, nesting on rocky cliffs. W. Leon Dawson (1923) writes:
The nest, which is an immense pile of sticks, lined with fine twigs and grass, and other soft substances, is usually placed on some lesser promontory or a sharp, inaccessible ridge near the ocean. The historic pile figured on page 1713 measured twelve feet by six on top, the larger diameter being along the crest of the ridge; and contained no less than two wagon loads of accumulated materials. Another, from which the M. C. O. took two heavily incubated eggs on the 20th or March, 1919, was built up on a slanting ridge, so that the lower or seaward face was fourteen feet in depth, although the top of the nest was only four feet by six.
There are probably more bald eagles nesting in Florida than in any other State in the United States, and they are quite thickly concentrated in certain favorable localities. Donald J. Nicholson, who has had many experiences with them, has sent me some voluminous notes on these birds. Pinellas County on the west coast and Brevard County on the east coast seem to be the centers of abundance. Mr. Nicholson mentions an area 3 1/2 miles long and three-fourths of a mile wide, in which were seven occupied nests, three of them within a 1-mile circle, in Brevard County. The nesting season, he says, is quite prolonged, beginning sometimes in October, but usually not until November or later, and lasting all through winter and spring, even into June. There are two good reasons to account for such early nesting: First, it is desirable that the eaglets, which grow very slowly, have time to develop their protecting plumage before hot weather comes on early in spring; the hot sun might prove disastrous for the tender downy young, unless they were constantly brooded by their parents. Second, it is easier for the eagles to secure the large amount of food required by the eaglets during winter, when coots and other waterfowl are abundant.
Mr. Nicholson mentions only three kinds of trees used in Florida, pines, cypresses, and mangroves, with a decided preference for pines. He says the height from the ground varies from 20 to over 100 feet but is usually between 45 and 70 feet. Oscar E. Baynard, who has climbed to between 250 and 300 nests, has found them as high as 140 feet.
Walter J. Hoxie (1888) watched a pair of eagles building a new nest, using some material from an old nest. The female did most of the building, and the male helped by bringing material. He says:
Having at last a foundation of about a foot thick, and four or five feet wide, as near as I could estimate, they proceeded to remove the material from the old partially repaired nest for the completion of the new. The male bird worked fairly well at this task, and during the last day made at least three trips to one of the female. She apparently took great pains in the interior arrangements of her new home, frequently pulling out a quantity of trash upon the edge of the nest, and, after working around a while inside, tumbling it back again, shaking it up with great rustling of wings and scratching of feet, which sent showers of little twigs and dirt upon the watcher below.
It is well known that, in Florida, great horned owls habitually use unoccupied eagles' nests, but a record of both species using the same nest simultaneously is unique. J. Warren Jacobs (1908) describes the finding of a huge nest in Florida that measured 15 feet in height and 8 feet in thickness. An eagle was incubating a set of eggs on the top of the great pile, and an owl flew "from a rude cavity in the side of the eagle's nest, in which she had formed a nest and deposited two eggs," 4 feet from the bottom of the pile. Mr. Nicholson once found an eagle incubating a great horned owl's egg.
In other parts of its range the bald eagle has been known to choose a variety of nesting sites. In the Middle Atlantic States nests have been found in oaks, chestnuts, pines, gums, and other trees. Bendire (1892) quotes Capt. B. F. Goss on two nests that he found on the ground on islands in Neuces Bay, Texas. Of one he says: "It consisted simply of a few sticks laid on the bare ground, not enough to make a single tier even, and these were covered with bones, feathers, and fish scales, and the ground in the immediate vicinity was littered with the remnants of their food and the excrement of the young." The other was a massive structure at least 6 feet high and 5 feet in diameter; he saw it fully 2 miles away.
Robert Ridgway (1877) had a nest shown to him in a very unusual situation on an island in Pyramid Lake, Nev.: "This nest was placed inside an oven-like cave about half-way up the side of the perpendicular rocks which formed this portion of the shore. The entrance was about fifteen feet from the top of the rock, and the same distance from the water, so it was inaccessible by any means then at command; but it could be plainly seen by looking through a crevice in the top of the rock. This nest was a huge bed of coarse sticks laid on the floor of the cave, and scattered about were the bones of numerous animals which were carried as food to the young."
I saw a nest in Texas about 50 feet up in a big live oak. Other nests have been found there in pecans and in mesquites 10 or 15 feet high (Lloyd, 1887). On Santa Margarita Island, Lower California, Walter E. Bryant (1890) found a nest in a giant cactus.
Mr. Baynard told me that some pairs of eagles do not breed every year; they may repair the nest and remain in the vicinity all through the season without laying any eggs. This was true of one pair that he and I watched. If the first set of eggs is taken, the eagle often will lay a second set after an interval of four weeks or more. Mr. Baynard says this happens in about half the cases, according to his experience. In the one such case that I noted the interval was about two months, and the second set was laid in the same nest. But often another nest is used.
Eggs.--Two eggs almost invariably make up a full set for the bald eagle, sometimes only one, and rarely three; in two or three cases four eggs have been found in a nest, but these may have been the product of two females. The eggs vary in shape from rounded-ovate to ovate, the former predominating. The shell is rough or coarsely granulated. The color is dull white or pale bluish white and unmarked, though often nest stained. Very rarely an egg shows a few slight traces of pale brown or buff markings.
The measurements of 50 eggs from Florida average 70.5 by 54.2 millimeters; the eggs showing the four extremes measure 78.8 by 56.2, 71.1 by 57.6, and 58.1 by 47 millimeters. The eggs are ridiculously small for large a bird. (Compare the relative sizes of the eggs of the ruddy duck, the sandpipers, or the hummingbirds.) Consequently the little eaglet requires a long time to develop.
Young.--The period of incubation is about 35 days, according to the most careful observers, though it has been otherwise estimated. Both parents assist in incubation and in the care of the young. Mr. Nicholson tells me that at every nest he has visited after dark he has found both birds at the nest, one incubating or brooding and one perched near it. In one instance the incubating bird remained on the nest until the climber nearly reached it. Usually an eagle will leave its nest as soon as an intruder is seen approaching it, but occasionally one will sit closely until the tree is rapped. The food of the young seems to be about the same as that of the adult, to be referred to later. The behavior and development of the young will be discussed under the northern race, on which more information is available.
[EDITOR'S NOTE: Mr. Bent's discussion of the young "Northern Bald Eagle," the "race" (alascanus subspecies) referred to above, which appears on pages 339 - 343 of United States National Museum Bulletin 167, follows:
Young.--Dr. Herrick's careful and prolonged studies of eagles' nests have added greatly to our knowledge of the home life of these great birds. Much of what follows has been taken from his published papers (1924, b, c, and d, 1919, 1932, and 1933). He gives the period of incubation as 34 to 35 days under normal conditions, though interrupted incubation may require a somewhat longer time. Both sexes share in the duties of incubation and care of the young; of which he writes:
In conducting the shifts a rather definite formula was observed. The sitting bird would give a sharp chitter when wishing to be relieved; the mate, if within hearing, came to the eyrie, moved up close, and the exchange was quickly made. If the eggs were left for only the shortest time, they were carefully covered with a great quantity of grass, stubble, and other convenient nest material, and the scrupulous covering and uncovering process would sometimes last from five to ten minutes. . . .
The eagle is the greatest home-keeper of his class. His eyrie is his castle, which, as we have seen, he will at times defend against all comers. In it his eaglets spend the first ten weeks of their life--from mid-April until early July upon the southern shore of Lake Erie--and it is the occasional rendezvous, lookout point, and dining table for the elder pair for the remainder of the year.
In his final paper (1933) he writes:
Many times I have been impressed by the behavior of the mother eagle when rain or hail descended upon her down-clad young. As I approached the woods one mid-May morning the female eagle was on the nest, and whether because of seeing me or not, she presently withdrew to a tree-perch. Then, just as I entered the grove a brisk shower started, and the eagle at once returned to her young ones. Frightened at my ascent of the tower, she was off again, but, as the shower continued, returned a few moments after I had entered the tent. She stood facing the wind and rain, with half-open wings, and afforded good shelter for the month-old eaglets huddled beneath her. In a few minutes this shower passed, and as the sun broke out she went back to her perching tree and spread her drooping wings to dry, in precisely the attitude assumed in times of great heat and humidity. Now, a quarter of an hour had hardly passed before the clouds again closed in and darkened above us; another downpour was under way, and the faithful mother sped back to her charges, and there she remained fending them with her stalwart body until this final shower was over. . . . Branches of pine and other green vegetation were always brought to the Vermilion nests both early and late in the season, and leaves were occasionally eaten by both adult and young eagles, as proved by their castings, but what significance this may have, if any, has not been ascertained.
He says elsewhere (1924c): "In 1923, if our estimate of the incubation period is correct, Eaglet No. 1 spent seventy-two and Eaglet No. 2 seventy-four days, in this case continuously, in the eyrie. Allowing then from 10 to 11 weeks for the life of the young Eagles in the nest, about one-half of this period, or five weeks, is passed in the white and gray down stages and the other half in the juvenal dress."
Although often two, sometimes three, eaglets are hatched, the larger number is seldom raised to maturity, and often only one eaglet lives to grow up. The young hatch at intervals of a few days and the first one hatched, often the female, is larger and stronger than the other. The larger eaglet often abuses the smaller one and gets more than its share of the food, until the poor little one succumbs and dies of weakness and exposure. Dr. Herrick (1932) writes:
Two eaglets were hatched in that season on
about April 24 and 28, and the younger bird was handicapped not
only on account of its lesser age, but from the tempestuous
weather and the shower of abuse it daily received from its older
companion. The mother eagle constantly disregarded the needs of
its puny infant, but bestowed every attention on her more
vociferous offspring. Thus, on May 18, when the eagle brought in a
large fish, the older nestling got 76 pieces, but the younger only
2, and a bad drubbing from his nest-mate in the bargain. On the
following day rain and hail beat so relentlessly on the great nest
that this much abused eaglet, then hardly able to crawl beneath
the sheltering wings of its mother, finally succumbed and was
trampled into the great mass of withered grass that lined its bed.
It should be noticed that this harsh treatment of the younger bird
had often occurred when the parent was away and when there was no
contest over the food.
Both parents bring food to the nest and both assist in feeding the young. Dr. Herrick (1929) describes the process as follows:
The female eagle has been brooding her callow young, which are now in white down and about two weeks old. She deliberately rises, walks over to the carcass of a large fish, stands on it and begins tearing off small pieces of the flesh and passing them to the three eaglets, which line up before her.
Twenty minutes later the male drops on the eyrie and immediately joins his mate in the work of satisfying the appetites of their hungry brood. The old eagles bend to their task and pass up bits of food at the rate of about five to the minute. At least the passes are at this rate, but the proffered food is not always taken. It may indeed go the rounds, to be eaten finally by one of the old birds.
When the eaglets are older and strong enough to tear up their own food, they are taught to do so. A family feast, presided over by the mother eagle, who has just arrived with a fish, is thus described by the same observer (1929):
Her young, all aquiver with excitement, continue to crouch and squeal, with their wings half spread, but they seldom venture to advance. The old bird now seizes her quarry, which appears to be a lake catfish of about four pounds in weight, and with one foot drags it to the center of the nest.
Standing on it there, she begins ripping it
up without further ceremony. With swift thrusts of her bill she
detaches large pieces of the white flesh and, taking a glance
around at each upward stroke, swallows them in rapid succession.
Then to the nearest bird, which by this time has edged up to its
parent, she passes several pieces from bill to bill, and goes to
work again on her own account.
When eaglet number two has been served in the same fashion, she moves a few steps away; whereupon number one seizes the carcass and, spreading over it, claims it as his own. Squealing, with head down, but for some moments without touching a morsel, he warns all intruders away. Meanwhile the other eaglet, drawing nearer, with head extended, watches the feeding bird and, seldom venturing to interfere, patiently awaits its turn.
He relates (1924c) another instance as follows:
After a repast of a quarter of an hour the
first Eaglet gave way to the other bird which laid hold of the
prey with one talon, dragged it aside and set to work; not feeling
satisfied, however, the first bird went after the chicken again,
but was immediately warned off. For two minutes they stood with
wings raised, facing each other, like fighting cockerels, until
the bird which had taken first chance by an adroit thrust snatched
the chicken with one talon and, dragging it to the opposite side
of the nest, began treading it with both feet; after each hasty
mouthful it glanced around to watch its nest-mate. The robbed bird
stood still, as if dazed, for some moments, and after having
flapped a few times settled down to watch for another opening;
with lowered head it moved very slowly towards the feeding bird,
following its every movement intently, and now an interesting
thing happened: the Eaglet that was feeding tore out pieces of the
flesh and intestines and thrice offered them to Eaglet number two
who received them in bill and deposited them at his feet without
swallowing a morsel. He was not to be thus beguiled, however;
watching his chance, he seized the whole carcass and having
deposited it beside the proffered pieces went to feeding in
With the growth of the first plumage, when about a month old, the eaglet spends much time preening its new feathers and gradually disposing of its old gray down.
At this stage preening was the order of the day and for a week or more the young "bird o' freedom" presented a most ragged and disreputable appearance. When thus actively engaged, and with the eyes often closed, the light down was sent flying to the breeze; gray fluffy sprigs of their natal covering were clinging to all parts of the nest, to neighboring trees, and when the wind was right at a later time, some of it even floated into our tent. A pair of House Sparrows, which were then nesting in the side of the eyrie, were most diligent in collecting this treasured down, and in early June one would see these little vagabonds steal up to the edge of the nest, snatch a few coveted sprigs and hurry back to their retreat.
With the increase in size and strength comes an increase in activity, with more time devoted to play and exercise in preparation for flight. Activities begin by walking or jumping about the nest, which soon becomes trodden quite flat, picking up and playing with sticks, learning to grasp objects in the talons, and stretching and flapping their growing wings. With tail raised and head lowered the eaglet backs up to the edge of the nest and shoots its liquid excreta clear of the nest to form a "whitewashed" circle on the ground below. Later on the flight exercises begin in earnest, of which Dr. Herrick (1924c) writes:
After a while a simple routine is established--raising the wings until they seem to touch over the back, taking a few strokes and jumping; the flapping gradually comes to take their feet above the floor of the eyrie and at eight weeks of age they may be able to rise two feet or more in the air; this ability attained, they are liable to go higher and higher and in a fairly stiff breeze, which helps to sustain if not stimulate them, they begin to soar and hover. In 1922 we said "good-bye" to the Eaglets more than once before knowing the long practise they required to produce that perfect coordination of muscles and nerves which was necessary for confidence in the air. During the last week of regular eyrie life in that year they would sometimes rise to a height of fifteen feet, and soar for a full minute, going even beyond the confines of the nest and always with talons down to facilitate landing upon their return.
At last the day comes for the eaglets to leave the nest. Sometimes they do so voluntarily; but in some cases it seems necessary to use persuasion. In Dr. Herrick's (1924c) "first season with the Eagles the young seemed disinclined to leave their eyrie and were finally starved out and lured away." After two days of scanty feeding and two days of fasting, "as the old Eagle with the fish was circling just above the nest the Eaglet was jumping with legs rigid and flapping frantically; suddenly it leaped into the air, and for a second seemed to hang, as if poised over the eyrie; at that moment the circling Eagle began to scream, and swooping down at the hovering and now screaming youngster passed him within six feet; a minute later the Eaglet, still holding to the air, drifted fifteen feet or more beyond the margin of the nest; with vigorous wing-beats it began to move eastward, following the mother bird with the fish and made a full mile in its first independent flight; it finally landed in the branches of a tree on the edge of a strip of woods and doubtless was there allowed to feed on the tantalizing fish."
For some time after they leave the nest, probably all through their first summer, the young eagles associate with their parents in the home territory and frequently return to the nest or their favorite perches. But they are eventually driven out to earn their own living and seek new territory. They are never allowed to establish a breeding station near their parental home.]
Plumages.--When first hatched the downy young eaglet is completely covered with long, thick, silky down, longest on the head; it is "smoke gray" on the back, paler gray on the head and under parts, and nearly white on the throat. When the young bird is about three weeks old this light gray or whitish down is pushed out and replaced by short, woolly, thick down of a dark, sooty-gray color, "hair brown" to "drab." The plumage begins to appear on the body and wings, scattered brownish-black feathers showing on the scapulars, back, and sides of the breast, when about five or six weeks old; at this age the wing quills are breaking their sheaths. At the age of seven or eight weeks the eaglet is fairly well feathered, with only a little down showing between the feather tracks, and the flight feathers are fully half grown.
In fresh juvenal plumage the young eagle is uniformly dark colored "bone brown" to "clove brown" above and below; the flight feathers are nearly black, but there is usually a slight sprinkling of grayish white in the tail. This plumage is worn throughout the first year without much change, except by wear and fading, the under parts fading to "hair brown." After the first annual molt, the next summer, the plumage becomes paler and much mixed with white in very variable amounts. Individual feathers on the back, scapulars, and breast are more or less extensively white, those of the breast and belly being largely white in some specimens. I am not sure whether this is a second or third year plumage, or both; if the latter, the third year is whiter than the second. The tail is more extensively mottled with white than in the first year, and the feathers of the crown and occiput are broadly tipped with pale buff. After the next annual molt the plumage of the body becomes darker, much like that of the adult, but lightly tipped with white below and mottled with white on the rump and upper tail coverts; the latter and the tail are now quite extensively white; the head is mixed with white above, about half white and half brown, or nearly clear, dirty white below. This is probably the third year plumage. At the next annual molt, early in the fourth year, the bird assumes a plumage that is practically adult, with a pure-white head and tail; but usually remaining signs of immaturity are seen, such as a few brown feathers in the head and some dusky mottling near the tip of the tail. The length of time required to assume the fully adult plumage does not seem to have been positively determined, and it may take longer than I have estimated. Adults and immature birds have one complete annual molt, which is very gradual, and prolonged through spring, summer, and fall. The flight feathers are molted mainly during July, August, and September.
Food.--The large amount of food found in the nests of bald eagles containing young indicates that the eaglets, even when small, are fed on much the same food that the adults eat, or that the adults devour much of the food that is brought to the nest, or perhaps both. Mr. Pennock found in a nest with two very young eaglets, "certainly not over a few days old," an entire black duck, a headless black duck, and a headless mullet that had weighed 1 1/2 to 2 pounds. In another nest he found a partly eaten lesser scaup duck, and entire horned grebe, and three other grebes more or less mutilated. Mr. Nicholson says that the amount of food found in the nests is astonishing, and often much of it has not been touched. He lists rabbits, mostly marsh rabbits, other undetermined mammals, turtles, coots, Florida ducks, lesser scaup ducks, pied-billed grebes, little blue herons, snowy egrets, terns, killdeers, catfish (by far the most frequent species found and some up to 15 pounds in weight), black bass, seargeant fish, crevalle, pompano, and other fish. Under one nest he found between 40 and 60 skulls of mammals, about the size of rabbits. He has never found snakes in an eagle's nest, nor has he ever seen wool or bones of lambs, even in the heart of the sheep country. There is no doubt, however, that bald eagles do occasionally carry off lambs, as several good observers have seen them do it, and the bones have been found in and under their nests. Probably many of these were picked up dead, but sheep herders generally regard eagles as destructive enemies.
C. J. Maynard (1896) witnessed an attack by a bald eagle on a brood of young pigs; the old sow was defending them vigorously, but the eagle might have succeeded in securing one, if Mr. Maynard had not interfered. Dr. H. C. Oberholser (1906) gives many interesting details regarding the food of American eagles and says:
At favorable opportunities this eagle preys upon fawns, and pressed by hunger will sometimes attack a full-grown deer, particularly if the latter be wounded. Remains of a mule deer (Odocoileus canus) were found by Dr. E. A. Mearns in the stomach of one from the Mogollon Mountains, Arizona. Mr. E. W. Nelson is authority for the statement that in northern Alaska it feeds at times on young reindeer (Rangifer arcticus). Even the wily fox sometimes meets its fate at the talons of this powerful bird, as is shown by Mr. Vernon Bailey's report that at Provo, Utah, a farmer found a gray fox (Urocyon scotti) evidently just killed, which a pair of eagles was busy eating. Opossums (Didelphis) and raccoons (Procyon lotor) are sometimes captured, but the nocturnal habits of these animals probably account for their not being more frequently obtained. Mr. Thomas McIlwraith mentions that an eagle shot on Hamilton Bay, Ontario, had the bleached skull of a weasel hanging firmly fastened by the teeth into the skin of its throat, a gruesome relic of a former desperate struggle.
Among the smaller mammals rabbits are often eaten, occasionally prairie dogs are taken, and, where they are plentiful, tree squirrels and ground squirrels, or spermophiles, form a large part of the food of the bald eagle. Domestic dogs have been attacked and such small fry as rats and mice are sometimes taken to the nest. Eagles, like most hawks and owls, cast up in the form or large pellets the indigestible portions of their food, such as bones, fur, and feathers.
In certain places, particularly in winter, bald eagles live largely on waterfowl, mainly geese, brant, ducks, and coots. This eagle is perfectly capable of catching a duck on the wing and frequently does so; but oftener the duck is pounced upon in the water or forced to dive again and again until it becomes exhausted and is easily captured; frequently two eagles join in the chase, which gives the poor victim a slim chance to escape. I have seen two eagles chasing a black duck in the air until it was forced down into the water. Ducks killed by sportsmen are often picked up by eagles. In Florida coots (Fulica) are very abundant in winter and furnish a favorite food supply for the eagles. Dr. W. L. Ralph (Bendire, 1892) says that many are caught on the wing; he found the remains of 13 in one nest. The interesting account, in a letter from John W. Baker to Charles F. Batchelder (1881), well illustrates the eagle's method of attack and the coot's attempt at escape. The eagle came daily and alighted in the top of a tree near the river where large numbers of coots were feeding.
At the first sight of the Eagle the coots all huddled together, remaining so during his rest, swimming about aimlessly and casting uneasy glances up in the direction of their enemy. The moment the Eagle lifted himself from the perch, the Coots seemed to press towards a common centre until they were packed so closely together that they had the appearance of a large black mantle upon the water; they remained in this position until the Eagle made the first swoop, when they arose as one bird, making a great noise with their wings, and disturbance with their feet which continued to touch the water for the first fifty or one hundred feet of their flight. This seemed to disconcert the Eagle who would rise in the air only to renew his attack with great vigor.
These maneuvers were kept up, the Eagle repeating his attack with marvelous rapidity, until, in the excitement and hurry of flight, three or four Coots got separated from the main body; this circumstance the Eagle was quick to discover and take advantage of; it was now easy work to single out his victim, but usually long and hard to finally secure it. I have never seen him leave the field of battle, however, without a trophy of his prowess, though I have seen him so baffled in his first attempt to separate the birds that he was compelled to seek his tree again to rest.
On one occasion, after separating his bird from the flock; he spent some minutes in its capture--the Coot eluding him by diving; this frequent rebuff seemed to provoke the Eagle to such an extent that he finally followed it under the water--remaining some seconds--so long, indeed, that I thought him drowned; he finally appeared, however, with the bird in his talons, but so weak and exhausted that he could scarcely raise himself above the water, and for the first thirty or forty yards of his flight his wings broke the surface of the water; very slowly he made his way to the nearest tree, where he alighted, on the lowest limb, to recover his spent strength.
William Brewster (1880) says that on the Virginia coast--
Geese and Brant form their favorite food, and the address displayed in their capture is very remarkable. The poor victim has apparently not the slightest chance for escape. The Eagle's flight, ordinarily slow and somewhat heavy, becomes, in the excitement of pursuit, exceedingly swift and graceful, and the fugitive is quickly overtaken. When close upon its quarry the Eagle suddenly sweeps beneath it, and, turning back downward, thrusts its powerful talons into its breast. A Brant or Duck is carried off bodily to the nearest marsh or sand-bar, but a Canada goose is too heavy to be thus easily disposed of. The two great birds fall together to the water beneath, where the Eagle literally tows his prize along the surface until the shore is reached. In this way one has been known to drag a large Goose for nearly half a mile.
W. W. Worthington wrote to Major Bendire (1892) as follows:
The other day I noticed a Bald Eagle hovering over the sound, much the same as the Fish Hawk does when about to strike a fish. Suddenly he plunged down and grappled with what I supposed to be a large fish, but was unable to raise it from the water, and after struggling a while he lay with wings extended and apparently exhausted. After resting a minute or two he again raised himself out of the water and I saw he had some large black object in the grasp of one of his talons, which he succeeded in towing along the top of the water toward the shore a short distance, and then letting go his hold. He was then joined by two other Eagles and by taking turns they soon succeeded in getting it to the shore. Investigation proved it to be a large Florida Cormorant, on which they were about to regale themselves.
During most of the year fish of various kinds furnish the eagle's main food supply. Many are picked up dead on the beaches or along the shores of lakes and streams, as these eagles are good scavengers. The osprey is systematically robbed, as nearly every observer or writer has noted. The eagle, from some favorable perch, watches for the return to is nest of this industrious fisherman, heavily laden with its prey. As the eagle starts in pursuit, the osprey mounts into the air in an endeavor to escape, but the eagle is too swift and too powerful for him, and the weaker bird is eventually forced to drop his prize, which his pursuer often dives down and catches before it falls to the ground. Sometimes the struggle is quite prolonged, but rarely does the osprey escape. Sometimes the eagle fails to catch the falling fish and it may be lost to both birds. Occasionally two eagles join in the chase, when the osprey soon gives up. Mr. Nicholson says in his notes: "I heard the angry cries of an osprey and, looking up, saw a bald eagle chasing the bird. The eagle flew over it making several quick dives, which were easily dodged by the osprey. But before we realized it, the eagle made one quick dive, turning upside down with talons outstretched, and took the fish from the grasp of the osprey. The eagle sailed away with the spoils, as if nothing had occurred. The osprey turned silently, with no pretense of fight, and flew down the river."
But where there are no ospreys to rob the eagle has to do its own fishing. Dr. Oberholser (1906) writes:
Sometimes from its perch on the summit of a dead tree it launches downward and, falling like a stone, seizes its prey; sometimes it hunts on the wing, much like an osprey, and when a fish is perceived poises by rapid wing-beats, finally dropping into the water even from a great height, and not infrequently becoming almost completely submerged; then, again, it varies this last method by flying leisurely along near the surface of the water. Audubon mentions that along Perkiomen Creek near Philadelphia, Pa., he saw it on several occasions wading in the shallows and striking at the small fish with its bill; and other observers elsewhere have noted a similar habit. It has been seen scrambling over the ice of a pond, trying to reach the fish below; and Mr. W. L. Dawson, in his "Birds of Ohio," says that at the Licking Reservoir, Ohio, it is reported in winter to watch near the air holes in the ice for the fish that come from time to time to seek the surface. Mr. J. G. Cooper has seen it catch a flying fish in the air, and the amazing celerity necessary for the performance of such an exploit may readily be imagined.
Again he writes:
The bald eagle does not disdain carrion, and in some parts of the arid West it lives at times to a considerable extent on the cattle and smaller domestic animals that fall victims to drought or other catastrophe. . . . Wilson tells that on one occasion when many thousands of tree squirrels were drowned in attempting to cross the Ohio River not far from Wheeling, W. Va., and a great number drifted to the shore, a bald eagle for several successive days regaled itself on them. Carrion was found in the stomachs of two eagles examined by Dr. A. K. Fisher. Mr. Horace A. Kline has seen this bird along the Wakulla River in Florida feeding on the carcass of an ox, again that of a sheep. . . . sometimes it drives away the gathered vultures or dogs from their repast and keeps them at a respectful distance until its hunger is satisfied. Furthermore it does not hesitate even to pursue the vultures and compel them to disgorge, when if it fail to catch the coveted morsels before they reach the ground it alights and devours them. Audubon relates that on one occasion he saw it kill a vulture that for some reason was unable completely to disgorge.
Stories of eagles carrying off babies or small children are probably greatly exaggerated or imaginary, but Wilson (1832) relates the following: "A woman, who happened to be weeding in the garden, had set her child down near, to amuse itself while she was at work; when a sudden and extraordinary rushing sound, and a scream from her child, alarmed her, and starting up, she beheld the infant thrown down, and dragged some feet, and a large Bald Eagle bearing off a fragment of its frock, which being the only part seized, and giving way, providentially saved the life of the infant."
Apparently eagles do not attack the larger and more formidable birds, such as Ward's herons, American egrets, or sandhill cranes. Mr. Nicholson tells me that he has never found the bones or feathers of these birds in the eagles' nests and that on three occasions he has found the cranes nesting within plain sight of occupied eagles' nests and within 100 or 200 yards.
Behavior.--The flight of the bald eagle is powerful and impressive, but not so graceful or inspiring as that of the golden eagle. Its ordinary traveling flight appears heavy and labored, as it moves steadily along with slow beats of its great wings, but it is really much swifter than it seems, as is often the case with large birds. But in pursuit of its prey it develops marvelous speed, which the swiftest wildfowl can seldom escape. It often sails along on a level course on widespread wings for a considerable distance; again it soars in great circles to an immense height, from which it sometimes makes a thrilling dive at terrific speed on half-closed wings.
About its nest the bald eagle is an arrant coward, leaving the nest as the intruder approaches, flying about at a safe distance and squealing, or perching on a distant tree to watch proceedings. I have never had one even come within gunshot range when I was near the nest. Mr. Nicholson, in all his experience, has never had an eagle even threaten to attack him, except on two occasions, both by the same pair. In one case he was attacked by both birds, swooping alternately within 6 or 8 feet of him. Bendire (1892) mentions three cases where the eagles have attacked men attempting to rob the nests, but in no case was the man actually struck. The fierceness of eagles has been greatly exaggerated. They are really mild-tempered birds and often make gentle and devoted pets, when raised in captivity. They are easily raised, if not taken from the nest when too young; but they require an astonishing amount of food.
Voice.--The voice of the bald eagle seems to me to be ridiculously weak and insignificant, more of a squeal than a scream, quite unbecoming a bird of its size and strength. Dr. Ralph (Bendire, 1892) says: "The cry of the male is a loud clear 'cac-cac-cac,' quite different from that of the female, so much so that I could always recognize the sex of the bird by it; the call of the latter is more harsh and often broken." Ralph Hoffmann (1927) says: "The cry of the Eagle, heard oftenest near its nest, is a high-pitched very metallic kweek kuk kuk, kweek-a-kuk-kuk with the quality of an unoiled castor."
Field marks.--An adult bald
eagle is unmistakable, with its pure-white head and tail and its
dark brown body; the head is conspicuous at a great distance, when
the bird is perched on a tree, especially against a dark
background. The juvenal first-year bird is uniformly dark colored
and is easily confused with the golden eagle; but it lacks the
golden hackles on the neck and head, and the young golden eagle
has more white on the basal half of the tail than the first year
bald eagle. Older bald eagles show more or less white on the
breast and belly, which the golden eagle never shows. Both species
show more or less white in the immature tail, but the bald does
not have such a distinct dark band as the golden. I have noticed
also that the head and neck of the bald eagle are stretched out
much longer in flight than in any of the other hawks or eagles,
except the caracara.
Bald Eagle* Haliaeetus leucocephalus [Southern Bald Eagle]
*Original Source: Bent, Arthur Cleveland. 1937. Smithsonian Institution United States National Museum Bulletin 167 (Part 1): 321-333. United States Government Printing Office