The most common breeding species in the Pribilof Islands, it is an abundant resident from the spring through the fall. Individuals begin to return to the islands in late March or early April with substantial numbers present by mid-late April. Many thousands are present by the beginning of May, with breeding commencing during the first half of June. The breeding populations estimated for the three main Pribilof Islands are 500,000 breeding pairs on St. George Island, 25,000-50,000 breeding pairs on St. Paul Island, and 15,000 breeding pairs on Otter Island. It is similarly abundant through the breeding season until late August or early September when numbers begin to decline. Substantial numbers are still likely to be found through much of September, though this species has typically left the breeding cliffs by the middle of the month and numbers continue to decline into October. Typically only small numbers are seen from October on but the combination of sea ice and weather systems may produce large counts from land or conversely can make for1 very few sightings locally. The species is pelagic during the winter and is present around the islands year-round.