Herbert W. Brandt found only one nest of the Baird sandpiper near Hooper Bay, Alaska, which he tells me—
Was on a dry mossy ridge amid the dunes and was partially concealed by the surrounding curly grass. It was flimsily constructed of grass stems and filled with a scant handful of small leaves of the dwarf birch and blueberry, together with a few adjacent reindeer-moss stems. The measurements of this nest were: Inside diameter 2½ inches, and depth perhaps 2 inches.
Eggs.—The Baird sandpiper lays ordinarily four eggs, occasionally only three. These vary in shape from ovate or ovate pyriform to subovate, and they have a slight gloss. In color they often resemble certain types of western sandpipers' eggs, as they are usually of a decidedly reddish tone; but they are considerably larger. The ground color varies from "pinkish buff" to "pale pinkish buff" or from "olive buff" to "cartridge buff." Three quite different types are represented in my collection. In the western sandpiper type the "pinkish buff" ground color is quite evenly covered over the whole egg with small, elongated spots, somewhat thicker at the larger end and having a spiral tendency, of "Hay's russet" and "chestnut brown," with a few underlying spots of "brownish drab." Another set has a "cartridge buff" ground color, which is unevenly covered, chiefly at the larger end, with small spots of duller browns, "bister," "Saccardo's umber," and light shades of "brownish drab." This seems to be the commonest type. An unusually beautiful set has a "pinkish buff" ground color, sparingly sprinkled with minute brown dots and boldly blotched with great, irregular splashes of deep, rich browns, "chestnut," "chocolate," and "liver brown," overlying large splashes of various shades of "vinaceous gray." The measurements of 54 eggs average 33.1 by 23.8 millimeters; the eggs showing the four extremes measure 33.5 by 24.4, 34.3 by 24.6 and 30 by 22 millimeters.
Young.—Incubation is shared by both sexes, but we have no data as to its duration. Mr. Dixon (1917) found the male bird covering the eggs more often than the female, and others have reported finding the male caring for the young. Mr. Dixon (1917) says of the young:
The young sandpipers were found feeding in the shallower pools, where the water was less than 1 inch deep. At times as many as five were noted in an area 1 yard square. They congregated along the water's edge, picking up, as the tide slowly receded, many bits of food. The nature of this provender I could not make out, although the young birds would often come within 20 feet of me when I remained motionless for a few minutes. The old birds were much more shy, often taking flight or retreating to distant gravel bars upon my approach. Considerable time was spent by both young and old in making short flights about the harbor. These flights alternated with periods of food getting, and were seemingly in preparation for the fall migration. It was only a few days then until the bulk of the species left on their southward journey.
Plumages.—The downy young Baird sandpiper is well colored to escape detection on the brown tundra moss. The crown and upper parts are variegated with black and "tawny" in an irregular pattern and dotted with white terminal tufts; the crown is centrally "tawny," with a median black stripe, and is bordered with black; the forehead, back to eyes, sides of the head and all under parts are pure white; there is a black spot in the center of the forehead, a black stripe from the bill, through the eye, to the occiput and another below it and parallel to it; there is a white superciliary stripe and some white mottling on the back of the head and neck.
The juvenal plumage is equally concealing. The crown is sepia with buffy edgings; the back and scapulars are dark sepia with broad white edgings; the wing is like the adult except that the coverts and tertials are edged with "pinkish buff" and tipped with white; the under parts are like the adult but the breast is more pinkish buff and more faintly streaked. A partial postjuvenal molt, including most of the body plumage and some of the scapulars, wing coverts, and tertials and takes place in October or later. I have seen birds in full juvenal plumage as late as October 3; young birds migrate in this plumage. At the first prenuptial molt the following spring young birds become indistinguishable from adults.
Adults have a partial prenuptial molt in April and May, including only part of the body plumage. The postnuptial molt begins in July, when the body plumage is molted before the birds migrate; the wings are molted after the birds reach their winter home, from December to February, not long before they started to migrate north again. I have seen birds in full nuptial plumage as early as May 1 and as late as July 29, and in full winter plumage as late as April 5. The adult nuptial and winter plumages are somewhat different; the colors are brighter and richer in the spring and the markings are more distinct; in the fall the upper parts are nearly uniformly buffy brownish with dusky shaft streaks; the chest and sides of the breast are dull brownish buff and not distinctly streaked.
Food.—Preble and McAtee (1923) found in the stomachs of three Baird sandpipers, taken on the Pribilof Islands, amphipods, algae, ground beetles, and a weevil. Mr. McAtee (1911) includes this species among those that eat mosquito larvae, crane-fly larvae, grasshoppers, and the clover-root curculio, all injurious insects. It feeds on the open mud flats with other species of sandpipers, but seems to prefer to feed about the edges of the shallow inland pools or where the muddy flats are partially overgrown with grass. William Brewster (1925) watched some of them feeding, of which he says: