The number sounds arbitrary until you have watched what happens when a boat comes closer. Seabirds nesting on exposed rock have no cover and no second chance; a single flush can send adults off their eggs long enough for gulls to take them, or leave chicks exposed to sun and cold. Harbour seals hauled out on a ledge will pour into the water at the first disturbance, and pups can be separated from their mothers in the rush. The buffer exists because these islands offer no room to retreat. All but three of the eighty-three are designated wilderness - the San Juan Wilderness, 353 acres, created in 1976 - which is a formal way of saying that on these rocks, human absence is the management plan.

For such a small total acreage, the range of habitat is wide. At one end are islets that amount to little more than a reef with a high-water mark, kelp streaming from their edges. At the other are islands big enough to carry grassland or forest. In between, and most valuable of all, are the ones with high cliffs. Vertical rock above deep water is close to ideal for nesting marine birds: inaccessible to land predators, near the food, with ledges enough for a colony. Puget Sound and the Strait of Georgia produce the feed; these scraps of stone supply the real estate. The refuge exists because the archipelago's larger, friendlier islands were long ago settled, farmed and built on, and the birds went where people would not follow.

About 200 species of bird pass through the islands in the course of a year. The regulars read like a catalogue of the northwest coast: gulls and cormorants, pigeon guillemots, auklets, tufted puffins, black oystercatchers working the tideline, killdeer, brant, and bald eagles watching the whole operation from the tallest available perch. Harbour seals haul out on the ledges and are common in the water around them, as are whales moving through the channels. Black brant have historically used the kelp beds here as winter feeding grounds, grazing eelgrass and algae in the shallows before continuing along the flyway. None of it is spectacle staged for anyone. It simply goes on, a few hundred yards from passing boats, unbothered as long as those boats keep their distance.

Three places break the rule. Five acres of Matia Island and all of Turn Island are run as state parks jointly with the Washington State Park System, and Smith Island and Minor Island are excluded from the wilderness designation. Matia is the one most people can actually reach: a cove with a dock, a five-acre campground, and a single one-mile trail that loops through the wilderness and back. It is about as modest as public access gets, and that is the point. The trail lets a handful of visitors walk through the kind of place the other eighty-two islands are, so that the refuge is not purely abstract - somewhere you have heard of and will never see. Come by boat, tie up in the cove, walk the mile, and leave the rest of it alone.