On the coast of British Columbia and farther south it is an abundant fall migrant, but it is rare or casual inland; the first arrivals sometimes reach California before the middle of July. Migration records for the great interior are almost entirely lacking and how it reaches the Atlantic coast, where it is so abundant in fall and winter, is a mystery.
Mr. Nichols wrote to me as follows:
The occurrence of this bird on the North Atlantic coast of the United States is irregular. At times it is really numerous on Long Island over periods of several years, and then it becomes rare again. In the 1912 southward migration the western was carefully looked for among the abundant semipalmated sandpiper but no evidence of its presence was found. In 1913 a single bird with a very white head and a peculiar note suggesting a young robin was, I now feel confident, a western sandpiper, at the time it passed as unidentified. The following year one of the white-headed long-billed juvenal westerns was picked out in a flock of semipalmated in August and collected. Later several others, all well-marked birds were identified in flocks of the semipalmated. In 1916 and 1917 the species was still more numerous. On October 12, 1917, at Long Beach with R. C. Murphy it was estimated that about one-half the Ereunetes were this, one-half the common eastern form. Specimens of each were obtained from gunners present. The following year (1918) a flock on the beach in late spring (June 2) were predominatingly western; the species returned again from the north in early July (July 4). During this or the immediately succeeding southward migrations the semipalmated fell off in numbers, and furthermore, a great many birds thought to be western were indeterminate. Mr. E. P. Bicknell met the same condition which I found at Mastic further west at Long Beach. I remember a letter wherein he spoke of the semipalmated being replaced by the western, but I did not take just that view of it. For a year or two I have no real idea how common either species was. I saw numerous birds that seemed to be western, but mostly indeterminate, and took no specimens. Later the standard semipalmated reestablished its usually large numbers and this season (1925) probably for the first time the western was again common among them, about as in 1916, some of this latter form easily identifiable birds (in life).
Winter.—Arthur T. Wayne (1910) says:
The western sandpiper is the most abundant of all the waders that winter on this coast. It is not unusual to see thousands of these birds any day during the winter months. It can almost be considered a permanent resident, as it is only absent from May 20 until July 8. The adults arrive in worn breeding plumage and immediately begin to moult the feathers of the head and throat. By the first week in August they have acquired their autumn plumage.
Among the big flocks of small sandpipers that we saw all winter frequenting the extensive mud flats in the vicinity of Tampa Bay, Florida, I am satisfied that this species was well represented, if not the predominating species. I confess that I can not identify in life more than a very small percentage of these little "peep," and then only when seen under most favorable circumstances. One dislikes to shoot any number of the gentle little birds for identification. But what few we shot proved to be western sandpipers, and I am inclined to think that most of them were. Mr. Nichols writes to me:
In my limited experience mauri is commoner than pusillus on the west coast of Florida. In Wakulla County in March and September, 1919, most all the Ereunetes were western, only one or two among them definitely identified as pusillus; and in April, 1917, two or three western were identified with least sandpipers south of Sanibel Light.
DISTRIBUTION
Range.—North America, Central America, the West Indies, and northern South America.
Breeding range.—So far as known, the western sandpiper breeds only in Alaska. North to Cape Prince of Wales, Cape Blossom, Point Barrow, and Camden Bay. East to Camden Bay and St. Michael. South to St. Michael, Pastolik, and Hooper Bay. West to Hooper Bay, Nome, and Cape Prince of Wales. It has been taken in summer in northeastern Siberia at two points, East Cape on July 14, 1913, and Cape Serdze, on July 16, 1913.