The adults begin to reach Cape Cod in August, but the main flight comes in September, consisting partially of young birds; most of the young birds come in October and some linger as late as November 10. While with us the white-rumped sandpiper frequents the wet meadows and marshes near the shore, as well as the sand flats, mud flats, and beaches, feeding at low tide singly or in small flocks and usually associated with pectoral, semipalmated, or least sandpipers. During high tides, while the flats are covered, this species may be seen on the high sandy beaches, mixed in with the vast flocks of small shorebirds, sleeping, or resting, or preening their plumage, while waiting for feeding time to come again; if the wind is blowing, all the birds are facing it; many are crouching on the sand and others are standing on one leg with the bill tucked under the scapulars. These flocks often contain hundreds and sometimes thousands of birds, mainly semipalmated sandpipers, semipalmated plover, and sanderlings. They are not all asleep, however, for if approached too closely, they all rise and whirl away in a vast shimmering cloud, flashing now white and now dark as they turn, and settle on the beach again at no great distance. _Winter._--August finds the white-rumped sandpiper migrating along the coast of Brazil and it has been known to reach Cape Horn as early as September 9. Doctor Wetmore (1926) writes: The white-rumped sandpiper was the most abundant of the migrant shore birds in the regions visited in southern South America. The species was not recorded until September 6, 1920, when it appeared in abundance in southward migration on the lagoons at kilometer 80, west of Puerto Pinasco, Paraguay. The first flocks from which specimens were taken were adult females, and two taken on the date when they were first recorded had laid eggs a few weeks previous as was shown by the appearance of the ovaries. The southward migration came with a rush as the birds passed through the night as witnessed by their calls. The flight continued until September 21, when a dozen, the last seen here, were recorded. The birds circled about lagoons in small compact flocks or walked along on muddy shores, where they fed with head down, probing rapidly in the soft mud; anything edible encountered was seized and swallowed and the bird continued without delay in its search for more.