Herbert W. Brandt in his manuscript notes says:
The pectoral sandpiper usually chooses for its homesite the upland rolling tundra, but an occasional isolated pair was found on the dry grass lands of the tide flats. This species builds the most substantial of any of the shorebirds nests that we met with at Hooper Bay, for even after it was removed from the grassy cavity in which it was built the nest would often hold firmly together. The birds showed exceptional skill in the concealment of their homes and consequently they were very difficult to find for they chose a tract where the curly bunch grass grew abundantly and under its domed protection they constructed an excavation deep in the moss. Here a substantial nest is fashioned of grasses and tediously lined or rather filled with small crisp leaves of the low perennial plants that there, in a dwarf creeping form, are the only representatives of the great inland forests. The dimensions vary between the following extremes: Inside diameter 3 to 3½ inches; depth 13/4 to 2½ inches; and outside depth 3½ to 5 inches. We never observed other than the female carrying on the loving duties of incubation and seldom indeed was the male even in close attendance. The female is very difficult to approach on the nest because she invariably leaves it before the ornithologist draws near and consequently we spent many hours endeavoring to watch the shy bird return to her nest.
The behavior of parent birds about the nests seems to be variable. W. Sprague Brooks (1915) says:
On approaching the vicinity of the nest the bird would leave it quietly and walk slowly about feeding and showing no excitement whatever. This happened several times until I decided to watch the bird and see if by any chance she might have a nest. In a short time she walked to a bunch of grass a few feet from me and settled on the nest. Even while I was packing away the eggs she showed no concern. I had precisely the same experience with the other two nests.
On the other hand, Alfred M. Bailey (1926) writes:
On July 3 Hendee flushed a female from a set of four slightly incubated eggs. "The nest," he states, "was in a patch of marsh grass, similar to the location usually chosen by the phalaropes, except that the ground was not wet. The female fluttered away to a distance of about 30 feet and went through a remarkable performance in her attempt to decoy me from the nest. She crept about among the hummocks in a very unbirdlike fashion, uttering all the time a mouse-like squeaking."
Eggs.—Mr. Brandt in his manuscript notes has described the eggs so well that I can not do better than to quote him, as follows:
The eggs of the pectoral sandpiper are of particular interest because they are perhaps the most beautiful of the many handsome shore-bird eggs that are found in the Hooper Bay region. Their rich and contrasting colors, their bold splashed markings, and high luster make them veritable gems of oological perfection. In all nests that came under our observation four eggs constituted the complement, and these generally nestled points together amid the crisp leafy lining of their birthplace, standing most often at an obtuse angle to the horizontal. In outline they range from subpyriform to ovate pyriform. The exterior of the shell has a smooth, almost polished surface that reflects in many eggs a high luster. The ground color varies considerably from dull white to "cream buff" and even to "deep olive buff," but in all sets I have seen the ground color and markings follow the same shades and types in the same set of eggs. The surface markings are bold and individual, and appear as if they were daubed with a paint brush. These large rich spots are elongated and are placed parallel to the long axis of the egg, showing but little tendency to spiral. The heaviest markings are at the larger end, often merging into a large "chocolate" blotch, and in one case this rich blot of color covered more than a fourth of the egg. The color of the markings ranges from "walnut brown" and "sepia" to "chocolate" and "blackish brown," with "chocolate" the predominating shade. The underlying spots are prominent and numerous on some eggs, while on others they are almost wanting. They vary from "pearl gray" to "violet gray," with an occasional egg inclined to "Isabella color." In fact, each different clutch of eggs exhibits some individual interesting peculiarity.
My only set, taken for me by Mr. Hersey, would fit the above description very well, but it is not particularly handsome. The ground color is dull white or "pale olive buff," which is more or less evenly marked with small blotches and spots of "bister" and "bone brown." Mr. Murdoch (1885) says that they "may be distinguished from those of the buff-breasted sandpiper, which they closely resemble, by their warmer color." The measurements of 116 eggs, in the United States National Museum and in Mr. Brandt's collection, average 36.5 by 25 millimeters; the eggs showing the four extremes measure 38.5 by 25, 38 by 27, 34 by 24.9, and 35.5 by 24.5 millimeters.