This is an abundant fall migrant, which is found regularly in much smaller numbers, during spring migration. The earliest spring migrants usually arrive around May 15th and are present intermittently through the first week of June, though counts rarely exceed ten at this time. Few are found after June 10th, with the earliest southbound adults usually located in the summer during the final few days of June or the first week of July. Numbers build quickly with hundreds usually seen by mid-July and peak numbers of adults occurring at the end of July or beginning of August. Large numbers continue through August and much of September (mostly juveniles which peak later in August), with a gradual decline beginning during the first half of September. By October numbers have declined significantly, though they are still common, with most birds gone by the middle of the month. It has never been recorded as late as November.
This species has declined significantly in numbers since the 1800s and early 1900s with the decline and then suspension of the commercial harvest of Northern Fur Seals (Callorhinus ursinus) from the Pribilofs. Large numbers of turnstones (tens of thousands) were known to visit the islands to take advantage of the large supply of food created by the seal carcasses during the late summer and fall.
