As a person approaches one of these pools, in the latter part of August, little suspecting that anything will be found near them, these birds turn their backs, which so closely resemble the lichen covered granite as to render the birds indistinguishable. A nearer approach and they present their white breasts which afford a striking contrast with the surroundings. In a moment they run together and huddle into a compact flock before they take wing. I have, by firing at the proper moment, secured every individual composing a flock of over a dozen birds. If they fly they take to their wings with a sudden impulse and fly in a zigzag movement for a few yards then swerve to right or left continuing until another locality is reached, where they sit quietly until approached. This is repeated every tide and, as the birds are crepuscular also in their habits, their opportunities for becoming fat are nearly doubled. They acquire the fat in a short time. The thickness of the layer is often one-fourth of an inch and completely envelops the body. The least abrasion of the skin or a shot hole soon fills the surrounding parts with oil which has exuded from the wound, making the preparation of skins for specimens a very difficult matter. The flesh of these birds is peculiarly tender and richly flavored. At times I have gone out to shoot these birds for the table and with five discharges (of half an ounce of No. 12 shot) I secured on one occasion 82 birds. A heavy stick thrown in among them as they wade along the water's edge also knocks many of them over, for these birds seem so intent on procuring food that but little heed is given to the hunter.
William Brewster (1925) says:
Invariably among the tamest and most confiding of our so-called shore birds, they will usually permit one to approach, either on foot or in a boat, within 5 or 6 yards, while I have known a gun to be discharged into a flock with fatal effect, but without causing any of the birds which escaped injury to take wing. Like most obese creatures they are habitually sluggish, confining their wanderings afoot to limited areas, and exploiting these very deliberately, walking slowly and sedately in crouching attitudes, with measured steps, frequently stopping to thrust their bills listlessly a little way into the soft ground, or to pick up small morsels of food from the surface. Occasionally, however, one may see them running to and fro over the mud quite briskly and ceaselessly, perhaps incited to this comparatively unusual behavior by the example of other waders feeding close about them, for they are by no means averse to the companionship of several of the lesser kinds, such as semipalmated plover and sandpipers, grass-birds, dunlins, etc. Although somewhat loath to take wing, even when threatened by obvious danger, they are likely to fly swiftly and far, when once started, doubling and circling over the marshes in much the same manner as other small sandpipers.
John T. Nichols, says in his notes:
When startled, a bird has been seen to crouch down concealing the bulk of its white underparts and practically disappear against the brightly lighted mud flat on which it had been feeding. This is a habit shared by its close relatives the pectoral and least sandpipers.
Voice.—The white-rumped sandpiper is ordinarily a rather silent bird, but its short, sharp flight note is characteristic of the species and serves to distinguish it readily in the field. To me it sounds like tzeep or tzip; Mr. Nichols calls it "a squeaky mouse-like jeet"; Mr. Brewster (1925) describes it as "a feeble lisping zip or tsip, fringilline, rather than limicoline, in character"; and Doctor Townsend (1905) thinks that "it suggests at times the call note of the pipit." C. J. Maynard (1896) refers to "one cry in particular, being loudly given and greatly prolonged, resembling the scream of a rapacious bird more than the whistle of a sandpiper."
Field marks.—The best field mark for this species is the white rump, or rather upper tail-coverts; this is conspicuous in flight but is usually concealed by the wings when the bird is on the ground. I have noticed that, while the bird is standing with its side toward me, the gray of the upper parts extend down on the sides of the neck as far as the bend of the wing, whereas in the semipalmated sandpiper, with which it might be confused, there is a decided white space in front of the wing.
Mr. Nichols says in his notes:
This bird is a size larger than least or semipalmated sandpipers, and at favorable angles shows a diagnostic white patch crossing above the rather dark tail. This white patch is a good example of color which apparently functions as a recognition mark. If the same were fortuitous one would not expect the tail to be darker than in related species, as is the case, causing the white rump to show more prominently. Straight bill, (or with slight decurviture at the tip, like that of the pectoral sandpiper) and as a rule finely and sharply streaked head and breast prevent chance of confusion with the European curlew sandpiper, of casual occurrence on our Atlantic coast.