Ernest Gibson (1920) says of this species, at Cape San Antonio, Buenos Aires:
This is certainly our commonest wader, and is found everywhere in flocks, from, say, the end of October to the middle or end of March. The number in these gatherings is only restricted by the area of the feeding ground; hence, when large mud flats are available in the vicinity of our fresh or salt water lagunas and cangrejales, or at the subsidence of a flood, the flocks are sometimes of enormous size. The observer may see many acres of ground which look to be in continuous movement, the surface being alive with the restless throng of sandpipers running about and chasing each other, feeding, or taking constant short flights.
DISTRIBUTION
Range.—North and South America; casual in Europe.
Breeding range.—Although the white-rumped sandpiper has been noted in summer from Wainwright, Alaska, east to southern Greenland (Julianshaab), the only places where eggs have been taken are Point Barrow, Alaska; Herschel Island, Yukon; Taylor Island, Victoria Land; Fort Anderson and Rendezvous Lake, Mackenzie; and the southeast shore of Lake Nettilling, Baffin Island.
Winter range.—North to Paraguay (Rio Pilcomayo and Rio Parana); and Uruguay (Montevideo). East to Uruguay (Montevideo); Argentina (La Plata, Cape San Antonio, Bahia Blanca, Rio Chubut, and Puerto San Julian); the Falkland Islands; and Tierra del Fuego. South to Tierra Fuego; and southern Chile (Straits of Magellan). West to Chile (Straits of Magellan and Santiago); and Paraguay (Rio Pilcomayo).
Spring migration.—Early dates of spring arrival are: Florida, De Funiak Springs, May 12; Georgia, Savannah, May 17; South Carolina, Mount Pleasant, May 7, Frogmore, May 7, and Charleston, May 16; North Carolina, Cape Hatteras, May 2, Churchs Island, May 6, and Pea and Brodie Islands, May 15; Virginia, Smith's Island, May 14; District of Columbia, Washington, May 11; New Jersey, Long Beach, May 9, Trenton, May 12, and Bernardsville, May 14; New York, Mastic, May 11, Canandaigua, May 19, Rockaway Beach, May 21, and Freeport, May 22; Connecticut, Middletown, May 10, and New Haven, May 19; Rhode Island, Block Island, May 16; Massachusetts, Melrose, May 9, and Harvard, May 20; Vermont, Woodstock, May 14, Brattleboro, May 18, and Rutland, May 19; Maine, Scarboro, May 29; Quebec, Godbout, May 24, and Quebec City, May 27; Louisiana, Lobdell, May 14; Kentucky, Bowling Green, April 27; Missouri, Jacks Fork, May 15, and Sand Ridge, May 16; Illinois, De Kalb, May 8, and Elgin, May 11; Ohio, Canton, May 8, Berlin Center, May 11, and Youngstown, May 17; Michigan, Detroit, May 6; Ontario, Toronto, May 26; Iowa, Marshalltown, May 4, and Sioux City, May 7; Wisconsin, Whitewater, April 28; Minnesota, Wilder, May 5, Jackson, May 13, and Heron Lake, May 19; Texas, Brownsville, April 11, and Ingram, May 8; Kansas, Emporia, May 4, Lawrence, May 5, and Topeka, May 7; Nebraska, Neligh, May 1, and Peru, May 13; South Dakota, Sioux Falls, May 5, and Vermilion, May 9; Manitoba, Whitewater Lake, May 12; Saskatchewan, Ravenscrag, May 13; and Mackenzie, Fort Resolution, May 19, and Fort Simpson, May 26.
Late dates of spring departure from the wintering grounds are: Argentina, French Bay, March 7, and Guamini, March 8. In North America, late dates are: South Carolina, Mount Pleasant, May 30, and Frogmore, May 31; North Carolina, Raleigh, May 24, and Lake Ellis, June 15; Virginia, Smith's Island, June 7; Delaware, Lewes, June 8; Pennsylvania, Erie, June 4; New Jersey, Bernardsville, May 24, and Camden, May 24; New York, Castleton, June 2, and Long Beach, June 20; Massachusetts, Harvard, June 4; Illinois, Waukegan, June 9; Ohio, Painesville, June 14, and Lakeside, June 25; Ontario, Toronto, June 21; Iowa, Sioux City, May 30, and Keokuk, June 5; Wisconsin, Madison, May 30; Minnesota, Hallock, June 8; Texas, Lomita, May 22, and Gainesville, May 24; Kansas, Fort Riley, May 22 and Stafford County, June 6; Nebraska, Lincoln, May 20, Republican Fork, May 25, and Valentine, May 25; South Dakota, Forestburg, May 27, and Vermilion, June 5; North Dakota, Charlson, June 1; Manitoba, Reaburn, June 6, Duck Mountain, June 8, and Shoal Lake, June 20; and Saskatchewan, Kutanajan Lake, June 9, and Quill Lake, June 10.
Fall migration.—Early fall arrivals are: Saskatchewan, Indian Head, July 1; Texas, Tivoli, August 17; Minnesota, St. Vincent, August 4; Wisconsin, Lake Koshkonong, August 1; Iowa, Marshalltown, August 19, and Keokuk, August 21; Ontario, Toronto, August 23; Michigan, Lansing, July 29; Massachusetts, Marthas Vineyard, July 16, and Ipswich, July 24; Rhode Island, Providence, July 18, and Block Island, July 27; New York, Orient, July 24; New Jersey, Long Beach, July 7; Pennsylvania, Erie, August 29; Florida, Palma Sola, August 27; Paraguay, near Puerto Pinasco, September 6; and Patagonia, Orange Bay, September 9.