In the juvenal plumage the center of the crown is blackish brown, with "ochraceous tawny" edgings; the rest of the crown and nape are "deep mouse gray"; the feathers of the back are brownish black, broadly edged with "tawny" or "ochraceous tawny"; the scapulars and all the wing coverts are deep sepia, broadly edged with colors varying from "tawny" to buffy white, whitest on the coverts; the under parts are white, with a broad band of pale buff across the throat and breast; the flanks are somewhat tinged with the same color; the throat, breast, and flanks are more or less heavily marked with median dusky streaks. This plumage is worn through July and part, or all, of August. The postjuvenal molt of the body plumage begins in some birds about the 1st of August, but in others not until two or three weeks later. This produces a first winter plumage similar to that of the adult, but distinguishable by the faded juvenal wing coverts and a few retained scapulars and tertials.
The partial prenuptial molt of both young birds and adults comes rather late in the spring, April and May, and involves the body plumage and some of the wing coverts and scapulars. Adults also have a complete postnuptial molt, beginning in August and lasting until October. The winter plumage is similar to that of the purple sandpiper, but it is conspicuously marked on the breast and flanks with large triangular or circular spots of dusky, whereas the purple sandpiper usually has a plain gray breast in winter.
Food.—Very little seems to be known about the food of the Aleutian sandpiper, but probably its diet is very similar to that of the purple sandpiper, which has similar feeding habits. Both species are fond of frequenting rocky shores and stony beaches, where they seem to be gleaning food. Doctor Stejneger (1885) has seen them "at low water eagerly picking up Gammarids among the stones close to the breakers." Bernard J. Bretherton (1896) writes:
Large flocks of these birds were seen during February, 1893, but were not met with during other winters. They were met with on a low sand bar, after a protracted storm which had thrown up millions of sand fleas, upon which they were feeding so industriously as to be easily approached and to which feast they returned several times, even after their ranks had been thinned by raking charges of fine shot.
Behavior.—In many ways the Aleutian sandpiper reminds one of its near relative, the purple sandpiper, but it is even tamer, less suspicious, and quieter in its movements. We had plenty of chances to get acquainted with it in the Aleutian Islands. We met it, and collected the first specimen of it, on the first island that we landed on, Akun Island, and after that we saw it on every island we visited, though it was much more abundant on the more western islands. These bleak islands, with their forbidding, rocky shores and stony beaches, washed with cold spray or enveloped in chilly fog, are the summer home of this hardy little "beach snipe," as it is called by the natives. It moves about so quietly and deliberately, and its colors match its surroundings so well, that we were constantly coming upon it unexpectedly. It was usually so intent on feeding that it paid no attention to passers-by; it was often necessary to back off to a reasonable distance before shooting one, and I shot several with squib charges in an auxiliary barrel. It is the tamest and most unsuspicious shore bird I have ever seen. On this point Mr. Turner (1886) says:
It is not at all shy, depending more on its color to hide by squatting among the crevices of the dark lava rocks and thus be unobserved. When cautiously approached, these birds generally run to the highest part of the rock or bowlder which they are on, then huddle together before taking flight the moment after. This habit allows them to be nearly all killed at a single discharge of the gun. The native boys, having observed this habit of these birds, procure a club about two feet long, and when the birds huddle together before taking flight the club is hurled in such manner as to sweep all the birds off the rock. This manner of procuring these birds is practiced by the western Aleut boys to a great degree.
Dr. E. W. Nelson (1887) writes:
A pair were found feeding on a series of bare, jagged rocks, over which the spray flew in a dense cloud as every wave beat at the foot of the rocky shore. I shot one of them, and the survivor merely flew up and stood eyeing me silently from the top of a low cliff 20 or 25 feet overhead until it, too, fell a victim. Later in the day another was seen near the border of a small lake in the interior of the island. It ran nimbly on before me, over the mossy hillocks, stopping every few feet and half turning to watch my movements, just as a spotted sandpiper would do under the circumstances. When driven to take wing, it flew a short distance, with the same peculiar down-curved wings and style of flight as has the spotted sandpiper.
Hamilton M. Laing (1925) says that "on one occasion one was seen to swim nimbly from one rock to another rather than fly."