Part 47

Spring.--Like most of the shore birds, the semipalmated plover seems to be in a great hurry to visit the breeding grounds. While, in the region of Massachusetts he leisurely wends his way southward from about July 12 to the end of October, a period of four months, the spring flight rarely lasts little longer than a month, from May 7 to June 14. Wells W. Cooke (1912) says: “At least four-fifths of the dates on the spring migration of this species fall in May. This is true for the entire district between the winter and summer homes, and the dates indicate that the migration in the United States occurs chiefly between May 10 and June 1.”

Migration occurs both by day and by night. Flock after flock may be seen on favorable days flying north along a beach, and the distinctive calls of the bird may be heard at night. I have recognized them clearly on a foggy May night when the birds were passing over the city of Boston. There are also records of the striking of lighthouses by these plover during the night.

It is evident that late migrants flying north in the spring must be late in returning, if they rear families, while those that return early in July must have been the early ones to migrate north. On July 30, 1918, I saw three semipalmated plover flying north along the shore at Ipswich. They were in full cry, and I wondered whether they were very late spring migrants or early autumn migrants temporarily turning back, or sterile birds that had no interest in the breeding grounds.

Courtship.--In the latter part of May and early in June on the southern Labrador coast I have seen this bird flying about in circles uttering its loud and rapidly repeated courtship song. The song, which is entirely unlike the call note, may be heard, and the courtship performance watched, not only in the spring but in the autumn migrations, for there is a recrudescence of the amatory instinct at this season in most birds. The song, if such it may be called, is then generally given from the ground and may be likened to a whinny or to the sound of a bouncing ball. The notes are at first slowly repeated, but the speed increases until the notes follow one another so rapidly that they nearly run together. The birds that utter this song crouch low with tails spread and slightly cocked, wings partly open, and feathers, particularly of the breast and flanks, puffed out. Sometimes one walks in this way around another, sometimes two face each other, crouched motionless and then spring at each other and up into the air like fighting cocks. Sometimes one runs after another which, on taking flight is followed by the first, but the most amusing form of this courtship is where two, thus flattened, spread, and puffed, walk slowly side by side as if they were doing a cakewalk, all the time uttering their clucking song.

H. S. Swarth communicates the following notes regarding courtship seen in northwestern British Columbia: “On as late a date as June 25 a male bird was seen going through with the mating antics, following the female about with head lowered and breast puffed out to an absurd degree, uttering frequently a low call note.”

Nesting.--A mere depression in the sand without lining or with only a few bits of shells or grass generally constitutes the nest of this species. P. B. Philipp (1925), writing of his experience in the Magdalens, says: “A nest as such is not constructed. A shallow hollow is scratched in the sand, and this is lined with bits of dead eel-grass, or a hollow is scratched in a bunch of dead seaweed.” H. S. Swarth sends the following notes of his experience with the nesting of this bird in the Atlin region of northwestern British Columbia:

A pair or two are pretty sure to be found where favorable conditions exist, but as the species requires an expanse of sandy or gravelly beach and as such beaches are not the rule about the lakes of the region, there are long stretches of shore line where the plovers are not found. They avoid rocky or stony beaches that are so favored by the spotted sandpipers.

He found his first nest, an unusual one, on the shore of Lake Atlin on June 10, and thus describes it:

The “nest” was in hard-packed gravel in a hole about 1 inch deep and with practically vertical sides. This depression was nearly filled with small chips and a very few straws. The eggs were nearly perpendicular in the nest, points down. It must have been some little labor for the bird to make this excavation, for the gravel was hard enough to retain the shape of the hole throughout the rest of the summer. I returned to the spot in September and found the cavity still sharply defined.

Audubon (1840) says of his experience in Labrador that this plover forms no nest, but makes a “cavity in the moss, in a place sheltered from the north winds and exposed to the full rays of the sun, usually near the margins of small ponds formed by the melting of the snow, and surrounded by short grass.”

Eggs.--[AUTHOR’S NOTE: The semipalmated plover lays four eggs, often only three. They are ovate pyriform to subpyriform in shape, with little or no gloss. The ground colors vary from “buckthorn brown” or “clay color” to “cartridge buff,” “olive buff” or “pale olive buff.” They are boldly and irregularly marked with small or large spots or blotches of black, brownish black or very dark browns; some eggs are heavily blotched with “warm sepia” or “chestnut brown”; there are usually a few small underlying spots of “pale drab gray.” The measurements of 100 eggs average 33 by 23.5 millimeters; the eggs showing the four extremes measure =36.2= by 24.3, 35.5 by =25.5= and =29.5= by =22= millimeters.]

Young.--The duration of incubation is not known. In the allied ringed plover of Europe the period of incubation is stated by Dr. W. H. Bergtold (1917) to be 22 and 23 days.

In the past it has generally been assumed that, with the exception in the case of the phalaropes, the female among the shore birds incubates the eggs and takes charge of the young. Joseph Dixon (1927) says: “After several seasons’ experience with breeding shore birds in the north the writer has come to believe that in more of our Limicolae than is generally known it is a common practice for the males to take a leading part in domestic duties not only in incubation but also in the care and training of the downy young.” With specimens in hand during the breeding season, he found incubating patches in the male semipalmated plover, and he says that “the males did a large part of the incubation and that it was the males that were the most fearless in the face of danger when caring for their young.”

P. B. Philipp (1925), on the other hand, studying the nesting bird in the Magdalens, writes: “I judge that the female does most of the incubating, three birds shot off the nest being of this sex.” H. S. Swarth also sustains the side of the female, for he writes: “With binoculars it is often possible to distinguish the sexes of the plovers, and it could be seen that it was the male who tired first in such efforts [shamming injury] to deflect danger from the nest. Even when he withdrew entirely, the female continued her protests until we were well out of her territory.” Dr. L. B. Bishop (1900), however, reconciles both points of view, for he says: “Bare pectoral spaces showed that both sexes assisted in incubation.”

The young leave the nest and run after the parents almost as soon as they are hatched. Bishop (1900) in the Yukon River region found an egg that was already pipped. He says: “I removed the young bird from the shell, and within half an hour the down was almost dry, the eyes were open, and it could hop about on its ‘knees.’”

Dr. W. H. Osgood (1909) reports the following observation by N. Hollister on a downy young of this species: “Although it was perfectly able to run about as fast as the adults, it at once lay flat to the ground when approached, with head extended forward in the sand, making it very difficult to see, so closely did it match the ground in color.”

The actions of the parent incubating the eggs when a human intruder appears is well told by H. S. Swarth in a communication, as follows:

The breeding bird skulked from the nest at the first appearance of an intruder, and, after performing an unobtrusive retreat to a distant point, launched out in conspicuous protest at the trespass. The call notes served to summon the mate, and sometimes even another pair of birds, all hovering about overhead or racing close by over the sand. A liquid call note, not particularly loud, was uttered constantly, and both birds of a pair would go through the form of pretended injury, dragging themselves over the sand with drooping wings and spread tail.

In another case--

A bird was flushed, as it had been many times before, at a point 300 yards or more above the water line, and I sat down quietly to watch her from the shelter of a scrubby willow. She flew to a distance, but returned in a few minutes, to run aimlessly about over the gravel nearby. Gradually she drew away, running over and between logs and other drift, her manner changing from one of noisy protest to furtive withdrawal behind any available cover. Finally, about 20 minutes after I began to watch, she settled down on the gravel, as it developed, upon the eggs.

At Seal Island, off the southern point of Nova Scotia, I found several breeding pairs of semipalmated plover, here, probably, at its most southern breeding place. On one occasion I came upon a bird that performed the usual wounded bird act, falling on its side and fluttering its wings as if badly injured. Presently it made off, fluttering and dragging its spread tail on the ground, keeping up this method of progression for over a hundred yards, although I had stood still. I then walked in the opposite direction and found a downy young running off in company with the other parent.

On another occasion at Great Caribou Island, Labrador, one of these birds appeared greatly excited at my presence, alighting near me, bobbing nervously, and protesting in conversational tones. Then it flew away, but immediately returned and flew by several times within a few yards, apparently in great fury, but not daring to hit me.

Plumages.--[AUTHOR’S NOTE: In natal down the young semipalmated plover is darkly colored above. The entire upper parts, from forehead to rump, are mottled with “deep olive buff” and black. The auriculars and a broad band encircling the back of the head are velvety black; there is a distinct black stripe from the bill to the eye and from the lores to the auriculars. A spot under the eye, a ring around the neck, and the entire underparts are pure white.

In fresh juvenal plumage the crown, back, rump, scapulars, and wing coverts are “buffy brown,” narrowly edged with creamy or buffy white, the edgings broadest on the wing coverts; the lores, cheeks, and a broad band across the chest are “buffy brown” to “sepia”; the forehead, throat, a ring around the neck, and the entire underparts are white; the tail is like the adult, but tipped with “pinkish buff.” The buffy edgings mostly wear away before the partial postjuvenal molt, which occurs in late fall. The first winter plumage is like the adult winter plumage, except that some of the juvenal wing coverts are retained and the head is as in the juvenal. At the next molt, a partial prenuptial, the plumage becomes practically adult; only a few old wing coverts remain.

Adults have a partial prenuptial molt in the spring involving the body plumage, some scapulars and wing coverts, and a complete postnuptial molt from July to December; I have seen the wings molted as early as July 30 and as late as December 10. The sexes are alike in immature and winter plumage and not very different in spring, when the black markings of the female are duller or mixed with grayish brown. In both sexes in winter the black markings are replaced by grayish brown.]

Food.--The semipalmated plover is an active feeder and in this way is sometimes beneficial to man. In the stomachs of 12 birds shot on beaches I have found worms, small mollusks (Litorina, Mytelis), various crustaceans (Orchestia, Gammarus, Limnoria), and insects.

W. L. McAtee (1911) says that this bird eats the larvae of the salt marsh mosquito (Ædes sollicitans). Samuel Aughey (1878) investigated the relation of birds to insects in Nebraska during the great invasion of Rocky Mountain migratory locusts on the western prairies and plains of the United States from 1873 to 1876. Of 11 stomachs of this species examined, he found the average number of locusts in each was 38; of other insects, 19. Junius Henderson (1927) states that this plover “on coast, feeds largely on crustaceans, mollusks, eggs of marine animals, and insects; interior, feeds on locusts and other Orthoptera, and many other insects.” Audubon (1840) says: “At this period (September) they are now and then observed on plowed lands, where they appear to procure different species of seeds and insects.”

Behavior.--The behavior of this bird during courtship and in the care of the eggs and young has already been described. On beaches and mud flats it is sometimes difficult to see, notwithstanding its strikingly marked plumage. As the piping plover matches the dry sand, so the semipalmated plover matches the wet sand, its favorite feeding grounds. Here one may walk almost onto them without seeing them if they stand motionless, as they often do. While sleeping on the dry sand, even with the black and white markings in plain sight, they are also difficult to see. W. V. Praeger (1891) writes as follows of a wounded bird he observed hiding in a hollow in the sand: