Murie, Olaus J. (1959) FAUNA OF THE ALEUTIAN ISLANDS AND ALASKA PENINSULA, 1936-38, U.S. Dept. Interior, Fish & Wildlife Service, Washington. pg. 111
Haliaeetus leucocephalus: Bald Eagle
Haliaeetus leucocephalus alascanus
Atka : Tig-a-lach
Alaska Peninsula: Tikh-lukh (Wetmore)
The bald eagle is commonly distributed throughout the length of Alaska Peninsula and adjacent island groups, and the Aleutian chain. It is numerous in some places. In the Aleutians, nearly every island that we visited had at least 1, often 2 or more, pairs, nesting. They are numerous about the larger islands. Williams noted 15 eagles in Bay of Islands, Adak Island, July 2, 1936, and more were found on other parts of the island. On June 29, we saw several at Kanaga Island. The caretaker of a fox- ranching establishment there had killed 14 of these eagles for the bounty, and he planned on raiding 20 more nests later.
For some reason, the bald eagle is scarce in the Near Islands- including Attu, Agattu, and Semichi. We observed a single pair on Agattu in 1937, but we saw none at Attu or Semichi and the natives assured us they were very scarce. However, we found a nest on Buldir Island, and from that point eastward bald eagles were common.
Not only do eagles occur along the Alaska Peninsula, they also occur on the offshore island groups. In 1940, Gabrielson observed them in several places at the base of Alaska Peninsula. At Kodiak, in 1936, one merchant erected a sign advertising the fact that eagle feet were acceptable as cash (bounty could be collected for them).
Plumage and Other Color Changes
Too few specimens were handled to obtain precise information on plumage changes. A. C. Bent (1937) states that he believes the bald eagle assumes the adult plumage in the fourth year. Field observations on numerous immature birds in Alaska were confusing, and we were unable to correlate some plumage patterns with age.
The downy-young plumages are well known and are well described by Bent. However, the color of beak, eyes, and other soft parts is not so well known. A young bird in the dark-down stage on Ananiuliak Island had a slate-colored upper mandible, the cere was of a similar color, but it was of a little lighter shade. The tip of the lower mandible was similar to the upper in color, but posteriorly the margin of the gape was flesh color, becoming paler posteriorly and shading into a near-yellow at the corner of the mouth. The lores were dull bluish. The iris was dusky brown, andthe pupil was blue. The eyelids were pale plumbeous. The feet were a yellowish-clay color, and the claws were slaty.
The first-year plumage is dark ; as Bent says, "uniformly dark '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." In the first year, both the bill and cere are of a blackish-slate color. The iris is brown, and the pupil is black. At this stage, the eyelids are still plumbeous.
The plumages preceding the final adult stage are hard to define. There appears to be much variation, probably over a 2- year period. Assuming a 2-year period for the post juvenal phases, the plumage varies in the degree of white mottling. The essential feature is a pattern that includes patches of dull-white mottling on scapulars and back (which, in flight, show as three distinct areas), and light-colored upper tail coverts and considerable white in under parts. In one phase of this plumage, which must be in the second year, the bill and cere are still blackish and the eye is still a rich brown. The preocular area is essentially white, the eyelid is plumbeous, and the gape is dull yellowish. The feet are yellow.
A later phase, which possibly may represent the third year, still includes the dark bill, with a dull-yellowish hue appearing on the lower mandible and the margin of the cere. The eye is dull yellow also, and a yellowish tinge is encroaching upon the preocular area. The eyelid is gray, and the gape is yellow. There is much light speckling on the head, though the head is chiefly brownish. The specimen on which this description is based did not have the light mottling on upper parts falling into a pattern of three light patches, as was seen on many birds; instead, it was more scattered.
In still another phase, which is quite advanced, the head is white, speckled with a blackish hue. The beak is a dull-yellowish one — perhaps best designated as tan, somewhat streaked with a slaty tone. The lower mandible is bright yellow at the base. The cere is a mixture of gray black and yellow. The eye is yeJlow (as in the adult), the eyelid is a brighter yellow, the preocular area is pale yellow, and the gape is a rich, bright yellow.
These are the advancing stages in development, the transition from dark "soft parts" to the characteristic yellow of the adult, but it was not possible to allocate all of these plumages to age groups.
Trees are absent in the area except in a limited portion of the base of Alaska Peninsula, therefore nests are placed on cliffs or pinnacles, or on low ground. Many nests are inaccessible to man by ordinary means of climbing. Frequently, a nest is placed on the top of a pinnacle, which sometimes is separated from an adjacent cliff by a narrow chasm, and which is surrounded by water, at least at high tide. At times, the nest is placed on a cliff, where it may be fairly accessible to man. In one case, on Buldir Island in 1936, a nest was found on a small rock outcrop on a slope, where one could walk to it without climbing. The same place was visited the following year; the former nesting site was abandoned, and the eagles (probably the same pair) had made their nest on the flat grassy valley bottom below. There was not even a hummock at the nest location.
In 1925, on Unimak Island, a nest containing eggs was placed on the top of a smooth sand dune. It is interesting to note that on June 9, 1941 (16 years later), Beals and Longworth re- ported finding an eagle's nest on a sand dune in the same locality. As a rule, eagles seek inaccessible locations on cliffs and obviously prefer pinnacles.
Nests are generally built by assembling a layer of dried grasses, mosses, and other vegetable debris. Sometimes kelp is used. Kelp nests are rimmed with the dried stems of Heracleum and Ligusticum, which are the largest material available in lieu of twigs from trees. In some cases, however, the eagles use sticks from the driftwood on the beach.
Eagles build various types of nests. The nest on the sand dune, already mentioned, consisted of a cavity that was 360 mm. wide and 130 mm. deep, heavily lined with dry grass, bits of moss, and a small amount of dead eelgrass from the beach. A number of large dry stalks of Heracleum lanatum lay around the rim, though these were not used in the construction of the nest proper.
Another nest was on a rock mass rising from a slope on Amak Island. A few dried plant stems were the only evidence of nest construction, and the single young sat on a bare spot, well trampled, on top of the rock, surrounded by a fringe of green grass.
Another nest on the same island was somewhat similar. It was on the grassy top of a high cliff. Two well-feathered young perched in a bare trampled spot about 8 feet long, which was crescent-shaped because of a hump in the middle of the space. There were the usual dry cow parsnip stems around the edge, but there was practically no nesting material in the center.
A third nest on this island was more substantial, consisting of dry grass with dry cow parsnip stems around the rim.
These scanty nests contrast sharply with a nest found at Amukta Island, June 16, 1936. This nest, on top of a pinnacle, was built of kelp, grasses, and driftwood to a height of 4 feet. A nest observed at Kanaga Island, June 29, 1936, was on the grassy top of a pinnacle; it was made mostly of moss and had a wide platform rimmed with dry stems of Heracleum and Ligusticum and a few driftwood sticks.
A nest on the grassy top of a columnar rock on the shore of Kiska Island was in the form of a bulky mass, consisting mostly of kelp.
Still another nest, on a rocky point of Little Sitkin, was built largely of dry stems of Heracleum and Ligusticum and willow roots, with a lining of finer vegetation. The willow there is a prostrate form, whose roots often are partly exposed by wind erosion.
These examples illustrate the general type and the variations of bald eagle nests. Some of the bulky nests resulted from an accumulation of material over a long period — a typical example was found at Amchitka Island, July 11, 1937. This nest — a shallow affair — was made mostly of moss on the grass-topped point of a pinnacle rising from the beach. It rested on a mass of old sod and soil to a depth of about 6 feet. This accumulation was filled with bird bones. Evidently, this accumulation had been built up by annual increment of debris left by nesting eagles for many seasons.
Our various expeditions were usually too late in the season to observe eggs — there were young in nearly every case. The number of young, in a series of 34 nests, varied from 1 to 3 per nest, though in 1941 Beals and Longworth reported a nest with 4 young. In 1 nest, there was 1 live youngster and 1 partly eaten dead youngster; in 2 other nests, there was 1 young and 1 rotten egg containing an embryo. All of these must be considered as having had two fertile eggs originally. On that basis, there were 12 nests with 1 young, 17 nests with 2 young or eggs, and 5 nests with 3 young.
In every nest that we observed, the nesting birds were white-headed adults. One report, from Cecil Williams in 1936, indicated a nesting pair, in immature plumage, on Uliaga Island.
I have discussed the food of this eagle in detail in "Food habits of the northern bald eagle in the Aleutian Islands, Alaska" (Condor, 1940, vol. 42, No. 4, pp. 198-202). The data presented were based on examination of 28 nests. In addition to this published material, data from 4 other nests are available, comprising 21 more food items. This additional material agrees with the published percentages.
In the Aleutian district, birds constitute the major part of the bald eagle's diet — 58.9 percent on the basis of material obtained in 1936; 86 percent for 1937. As would be expected, most of the birds taken are the so-called sea birds, chiefly shearwaters, fulmars, cormorants, glaucous-winged gulls, murres, ancient murrelets, paroquet auklets, crested auklets, and horned and tufted puffins. Fulmars and shearwaters head the list. Two ravens had been eaten. Others taken included: Petrels, kitti- wakes, pigeon guillemots, ptarmigan, least auklets, and ducks, though none of these are taken in great numbers. Ducks were not preyed on extensively, probably because of the abundance of other birds, although harlequin ducks, oldsquaws, European teals, pintails, common eiders, red-breasted mergansers, and three emperor geese were identified in food remains.
Mammals are not universally available to eagles in this district and are seldom found in the diet. The ground squirrel is by far the most common mammal captured. Others, which occasionally are taken, are the house rat, the field mouse, the blue fox, and, possibly, the domestic sheep at Umnak Island. In 1938, Scheffer reported that one of the men in charge of the sheep on Umnak Island declared that he had never seen eagles bothering live sheep, though they will eat carrion. Another informant, a sheep herder at Unalaska, said that eagles will not bother healthy sheep, but they will attack dying ones and will feed on dead ones. He had seen both ravens and eagles feeding on carcasses of winter-killed sheep. Beals and Longworth, in 1941, reported that local residents on Unimak Island believed that the bald eagle kills caribou fawns. However, this would need verification. It is known, of course, that eagles feed on dead whales and seals.
It has been thought that bald eagles kill many blue foxes. But, according to the evidence we obtained, this is not the case in the Aleutian district. The remains of only one fox were found in an eagle nest, and these remains could have been carrion because we found a few dead foxes on the beaches. To further refute this theory, many blue fox families were being raised successfully in the vicinity of eagle nests.
A moderate percentage of fish and invertebrates is eaten by the bald eagle. To what extent this eagle feeds on dead or spawning salmon on the Alaska Peninsula was not determined. In July 1911, at Morzhovoi Bay, Wetmore observed them feeding on dog salmon taken from shallow rapids. Edward D. Crabb (1923) apparently found fish remains to be prominent in nests examined along Alaska Peninsula; there were parts of seven Dolly Varden trout in one nest. Edward J. Reimann (1938) observed a bald eagle taking a mullet out of the water, reaching for it with one foot. Beals and Longworth found two sockeye salmon and the head of a sea gull in a nest on Unimak Island, June 9, 1941. We did not see bald eagles capture live fish, but Atka mackerel were often observed near the surface of the water, where an eagle could very easily seize one.
In the Aleutian chain proper, the main food of the bald eagle consists of sea birds. There are some indications that fish of various kinds are more prominent in the diet along the Alaska Peninsula, where we did less work on this bird. At any rate, there is abundant evidence that the eagle is not a serious detriment to man's interests throughout the Aleutian district.
A number of nestling bald eagles were banded in the Aleutian Islands in 1937. Of these, six returns were obtained. All six had been banded in June; 1 on Little Kiska Island, 2 at Little Sitkin, and 3 (all in one nest) on Rat Island. The following winter, all of these were killed by natives on Attu Island. This shows a westward drift of immature eagles, at least in the western part of the Aleutian chain.
These eagles are permanent residents in the Aleutian district, summer and winter.