In the six sets before me the ground color is uniformly dull white and is conspicuous. The markings are bold and individual, with most of them round instead of elongate, although there is a slight spiral tendency. These spots are dark, ranging from "claret brown" to "burnt lake," producing a deep red effect when examined in series. The underlying spots are numerous and rather conspicuous, due to the whitish ground color. They shade from "light Quaker drab" to "Quaker drab."
Less than half of my sets, all from Alaska, would fit his description; the ground colors in most of mine vary from "pale olive buff" to "olive buff"; in some it is "deep olive buff," and in one "Isabella color." The colors of the markings run from "liver brown" to "chestnut brown" in the darkest and from "hazel" to "cinnamon brown" in the lightest. There are comparatively few underlying drab markings. The eggs show the same variations in shape and arrangement of markings as eggs of the least sandpiper. I have two sets from Point Barrow, taken with the parent bird, which are almost exactly like eggs of the western sandpiper in color and style of markings but smaller, and several other sets approaching them in appearance. There are 10 sets of eggs in the Museum of Comparative Zoology in Cambridge collected by W. Sprague Brooks near Demarcation Point, Alaska, with the parent bird in each case. Three of these are of the western sandpiper type, and three others are similarly marked with different shades of brown. The measurements of 52 eggs average 30.2 by 21.2 millimeters; the eggs showing the four extremes measure 32 by 21, 30 by 22, 27.7 by 21.3, and 31.5 by 20 millimeters.]
Young.—According to Mr. Dixon (1917a), incubation lasts 17 days. It is performed equally by the male and female, as is shown by Mr. Brooks's very conclusive report quoted above. Mr. Dixon (1917a), writing of birds observed in Alaska says the young so exactly match the surroundings that they are invisible at 3 feet. He relates the case of a snowy owl that sailed from its perch in the direction of a brood of young which flattened and froze obedient to the alarm cry of the mother. The owl poised directly over them, but evidently failed to see them and flew away. On another occasion two parasitic jaegers flew by; the young flattened, and all escaped but one that began to move before the second jaeger had passed and was promptly snapped up.
He says:
It was found that the parents made no effort to feed the young. It was soon seen, however, that such care was not necessary. The young would stumble about and pick up minute gnats and flies with great dexterity, and the shallow algae-rimmed pools furnished them many a juicy "wriggler." The gait of the young sandpipers was a stumbling toddle, while their large feet and legs were all out of proportion to the rest of their slender bodies. By dropping and extending their wings they were able to use them as crutches, which often kept them from falling.
In about a month they were fully fledged, and a week later the sandpipers were leaving for the south.
Plumages.—[Author's note: In natal down the young semipalmated most closely resembles the young western sandpiper, but it is generally paler, with less brown or rufous. The forehead, sides of the head, and all under parts are white, faintly washed on the cheeks and upper breast with pale buff; a median stripe on the forehead, reaching only halfway to the bill, a broad loral stripe, and a malar spot are black; there is a black spot in the center of the crown, broken by a few very small white dots, surrounded by "hazel" and bordered with black; a short stripe over the eye and an auricular patch are black and "hazel" mixed; between these and the crown patch there is a broad band of white dots, terminal tufts; the back, rump, wings, and thighs are variegated "hazel" and black, with numerous small white dots, terminal tufts. The bill is broad at the tip.
Young birds are in juvenal plumage when they reach the United States on the fall migration. They can be distinguished from adults by the buffy edgings above and by the absence of dusky streaks on the throat and upper breast. The feathers of the crown are edged with sandy buff and those of the back and scapulars with "ochraceous buff" or creamy white; the wing coverts are edged with pale buff; the upper breast is washed with buff and the rest of the under parts are white. This plumage is partially molted during September and October, producing a first winter plumage, which is like the adult winter plumage, except for the juvenal wing coverts, some scapulars, and a few body feathers, which are retained. At the first prenuptial molt, the next spring, young birds become practically adult.
Adults have a complete molt from July to November, the body plumage being molted first and the wings last, the latter sometimes not until winter. Their partial prenuptial molt involves the body plumage, sometimes the tail and some wing coverts; it begins in February and lasts into May. The freshly molted spring plumage, in early May, has a "drab-gray" appearance, due to broad drab-gray tips on the feathers of the mantle; these tips soon wear away, revealing the bright colors of the nuptial plumage before the end of May.]