In the colored illustrations of 10 eggs before me, the shapes vary from ovate pyriform, the prevailing shape, to subpyriform. The prevailing ground colors are greenish olive, "ecru-olive," "lime green," or "grape green"; a few eggs are more buffy, "cream buff" to "deep olive buff." The markings are small, and often inconspicuous, spots, scattered quite evenly over the entire surface, but sometimes more thickly about the larger end. These are in dull shades of brown, "buffy brown," "snuff brown," or "sepia." They are not handsome or showy eggs. The measurements of 41 eggs, furnished by Rev. F. C. R. Jourdain, average 35.7 by 24.7 millimeters; the eggs showing the four extremes measure 38.2 by 24.7, 34.1 by 26.1, 33.1 by 24.4 and 35.3 by 23.5 millimeters.
Young.—Authorities seem to differ as to whether both sexes incubate or not. Both Feilden and Walter secured incubating males, but Manniche (1910) says:
Till the laying is finished both birds will faithfully accompany each other, but as soon as the brooding begins, the males will join in smaller flocks and wander around on the table lands and at the beaches of the fresh waters, often in company with Tringa canutus and Strepsilas interpres. They usually left the country some days before the middle of July. I secured several males for examination but never found the least sign of a breeding spot.
He gives the period of incubation as 23 to 24 days and says of the young:
The bursting of the egg shells will generally begin already some three days before the emergence of the young. The mother bird will immediately carefully carry the shells away from the nest in order not to attract the attention of ravens and skuas. Between the emergence of the young will elapse not more than a few hours; as soon as the latest born young one feels sufficiently strong; that is, when the down is dry, all the nestlings will leave the nest at the same time. If the old female considers the nearest surroundings of the nest to be unsafe or too difficult in food for the brood, she will immediately lead the young away. Thus I have met with newly hatched young ones, hardly one hour after their departure from the nest in a distance of 500 to 600 meters from this. In the cases concerned the disturbance by my frequent visits to the nests during the breeding may have caused the early departure.
In the following 12 to 14 days the chicks are guarded by their careful and extremely vigilant mother, who leads them over stony plains, by overflows of melted snow and fresh-water beaches; they are eagerly occupied in seeking food, which at this period exclusively consists of small insects and larvae and pupae of these. I have often observed that the chicks take shelter under the wings of their mother from the cold nights and the heavy showers. The chicks' power of resistance against cold and severe weather is relatively small.
When the sanderling wants to protect her young ones against hostile attacks she executes still more surprising systematic tactics than she does when brooding. Already when at a distance of some 200 to 300 meters from the young ones the old female would rush toward me and by all kinds of flapping and creeping movements in an opposite direction try to lead me astray; all the while she would squeak like a young one, and now growl angrily, striving to draw my attention toward herself only. Now and then she would rise very high in the air in a direct rapid flight, to disappear behind a rock on the opposite beach of a lake, etc. From quite another direction she soon appeared again just before my feet.
If I finally retired still farther away from the young ones and for a while kept myself hidden in the field, she would fly slowly, sometimes quite low, over the earth to the spot where the young still were lying motionless and mute, with their bodies pressed flat against the earth and their neck and head stretched out. When at last the female considers the danger to be over, she, flying or running close to the chicks, produces a short chirping song, at the tones of which all four young ones suddenly get up and begin to run about. Only in this case the sanderling produces its highly peculiar "sanderling song," which is very similar to the song of Sylvia curruca. As long as the young kept lying quiet on the ground in the before-mentioned attitude they were extremely difficult to find, if I had not from my ambush by aid of my field glass exactly marked down the spot where they last appeared. The young ones do not seek any real cover, as in hollows in the ground, under plants, behind stones, or similar natural hiding places. When I had found a single young one, which while I kept it in my hands began to chirp, it generally happened that the three other young, which had till then kept quiet, suddenly rose and, with the wings raised, uttered a quite fine mouse-like squeaking and hastily rushed away, while the old female, as if paralyzed, lay down before my feet, still squeaking exactly like the chicks.
Within 12 to 14 days the young ones are full grown and able to fly. Strange to say, the brood of the sanderling seems to suffer very little from hostile persecution, a fact which may be due to the accomplished vigilance and prudent behaviour of the old female and the young as well as the extremely suitably coloured clothing of these. I wonder that these defenceless small beings can avoid the Polar fox, which in this season more frequently than usual visits the domain of the waders, and which, as well known, has an excellent sense of smell.
Plumages.—The nestling sanderling is thus described in Witherby's Handbook (1920):
Forehead buff with a median black line from base of upper mandible to crown; nape buff, down with dusky bases; rest of upper parts variegated light buff, warm buff and black and more or less spangled white; lores buff, two black lines across lores toward eye; under parts white, cheeks, chin and throat suffused light buff.