In March their ranks are reinforced by newcomers which have wintered on more hospitable shores, and in the latter part of the month enormous flocks of 500 or more swarm along the beach, especially on the north shore. About one month later the great flocks dissolve into small companies, which, following the water courses, disperse over the whole island, settling in pairs on suitable places at the beaches, on the tundras, or on the mountain plateaus, this bird being in fact one of the most numerous and the most equally distributed species of land birds on the islands.
Courtship.—We frequently observed the charming song flight of this sandpiper in the Aleutian Islands. The birds were especially abundant on Tanaga Island, where we found them nesting on the little knolls or hummocks on the tundra in a large alluvial plain back of the beach hillocks. The males were very active and noisy, indulging in their hovering song flights, rising 30 or 40 feet in the air and fluttering down while pouring out a delightful twittering song. Also, while flying about or while standing on some prominent hummock, they gave their loud, musical melodious calls of the upland plover; these loud notes were not heard anywhere except on their breeding grounds and were probably notes of greeting or of warning to their mates. Doctor Stejneger (1885) writes:
It was in the late afternoon of the 28th of April, 1883, that I first witnessed this singing performance of the sandpiper. The bird rose from the Rhododendron tundra on the northern slope of Kamennij Valley, and while flying about on quivering wings, sometimes remaining quite still in the air, it uttered a loud, agreeable, and melodious twitter, which really must be called a "song," whereupon, with outstretched wings, it descended obliquely, seating itself upon the top of a tussock. Sitting there, with puffed plumage and pendant wings, it produced a loud "bleating," so much like that of Gallinago gallinago as to completely convince me that the analogous note of the latter is produced by the throat in exactly the same manner. During the "bleating" the whole bird was quivering with a tremulous motion as if in a high state of excitement. The voice was slightly more melodious than that of the snipe.
Nesting.—While wandering over the foothills of Kiska Island on June 17, 1911, I found my first nest of the Aleutian sandpiper. I was crossing a flat place, high up on a hill, covered with moss and scanty growth of grass, when the bird fluttered off almost underfoot, feigning lameness. The nest was a deep hollow in the moss, 3 inches in diameter and fully 2 inches deep, partially concealed by a few blades of scanty grass, and lined with dead leaves, a few straws, and a few feathers of the bird. The four eggs were only slightly incubated. I found a similar nest, containing three small, downy young, on Attu Island on June 23; the nest was on a little hummock on a hillside, a deep hollow, lined with dead leaves and bits of straw. It was the male bird that flew from the nest in both cases.
Austin H. Clark (1910) found a nest on Attu Island on the side of a mountain, 700 feet or more above the valley and near an extensive patch of snow. Alfred M. Bailey (1925) found a nest at Emma Harbor, Siberia, on July 4, 1921, containing three young and an egg; the nest was "on the shores of the bay, in gravel along the beach." He also found several nests the following season near Wales, Alaska; "the nesting sites varied from exposed depressions in the moss to well-concealed dried grass." A set of eggs in Edward Arnold's collection, taken by Sheldon and Lamont on Montague Island, Alaska, June 22, 1916, came from a nest "on débris just above tidewater."
Eggs.—The Aleutian sandpiper almost invariably lays four eggs, although five have been found. These are ovate pyriform in shape and have a slight gloss. The ground color is "olive buff" or "deep olive buff." They are heavily, boldly, and irregularly blotched, chiefly about the larger end, with a few scattering smaller spots. The markings are in dark browns, "chestnut brown," "burnt umber," and "seal brown," varying with the thickness of the pigment. There are underlying blotches of "brownish drab," producing very handsome eggs. They can not always be distinguished with certainty from eggs of the Pribilof sandpiper, as they vary greatly in size; they average smaller, but the measurements overlap widely. The measurements of 50 eggs average 38 by 26.6 millimeters; the eggs showing the four extremes measure 43.2 by 26.8, 39.4 by 28, 35 by 26.3, and 37.3 by 24.1 millimeters.
Young.—Incubation is apparently performed by both sexes, and both assist in the care of the young. The birds that I flushed from my two nests, one with eggs and one with young, both proved to be males. Mr. Turner (1886) says:
The males are much devoted to their mates while incubating, and I have every reason to believe that the male does the greater part of the labor of incubating, as they were the ones generally found either on or near the nests. When alighting near the nest either sex has the habit of raising its wings perpendicularly and slowly folding them, all the while uttering a trilling peep, continued for several seconds.
The parents are very devoted to their young, employing the usual tactics to divert the attention of the intruder, stumbling and fluttering over the ground, as if both legs and wings were broken. The young leave the nest as soon as they are strong enough to run, but remain with their parents until they are fully fledged in their first winter or juvenal plumage and ready to fly in August.
Plumages.—The downy young Aleutian resembles, in color pattern, the young purple sandpiper, but can easily be recognized by its warmer and richer browns. The upper half of the head is "warm buff," shading off to "pale buff" on the lores and cheeks and to pure white on the throat and neck. A median black stripe is broad on the crown, tapering to a point at the bill; loral and malar black stripes converge at the bill; the rest of the upper head is spotted or striped with black. The nape is a mixture of dull buff and dusky. The back, wings, and thighs are variegated with black, "ochraceous tawny" and "warm buff," everywhere sprinkled with conspicuous dots, terminal tufts, of buffy white in an irregular pattern; there is a more or less well-defined black patch in the center of the back, varying in different individuals, centrally veiled with "burnt sienna" tips. The entire under parts are pure white.