Iona was genuinely an island once, one of the low sandy bodies deposited at the mouth of the Fraser as the river drops the mountains it has been carrying. A causeway and Ferguson Road now tie it to Sea Island, so it is a peninsula in fact and an island only in name and in the paperwork. In the middle sits a primary sewage treatment plant, which runs public tours. Around it are settling ponds, an animal refuge, and Iona Beach Regional Park, managed by Metro Vancouver. Vancouver International Airport occupies the land immediately next door. It is difficult to think of a stranger assemblage of neighbours, and the birds do not appear to mind any of them.

The reason has to do with tide and timing. The Fraser delta is one of the most important shorebird staging grounds in the hemisphere -- a Ramsar wetland of international importance and a hemispheric reserve in the Western Hemisphere Shorebird Reserve Network -- and hundreds of thousands of birds refuel on its mudflats during migration. When the tide comes in and covers those flats, the birds need shallow water somewhere else, immediately. The Iona ponds are exactly that: warm, shallow, nutrient-heavy, and dependably wet no matter what the ocean is doing. Rarities turn up here that have no business being on this continent at all -- great knot and red-necked stint alongside the spoon-billed sandpiper, all Asian species blown or navigated far off course. Close to 300 species have been recorded, the second-longest list of any single location in western Canada. Public access to the inner ponds has been restricted in recent years to reduce disturbance.

Two jetties, both owned by the Government of Canada, run out from Iona into the Strait of Georgia. The south one, Iona Jetty, reaches nearly four kilometres offshore, and it is genuinely one of the strangest walks in the Lower Mainland. Twin gravel trails run along the top of and beside the large pipe that carries treated effluent out to deep water, so you are walking on the infrastructure, straight out to sea, with the river's silt plume on one side and open strait on the other. By the far end the shore is a distant line and aircraft are turning overhead on final. The North Arm Jetty is longer and far less used: a sandy bar rather than gravel and concrete, angling northwest parallel to the Vancouver shoreline, ending at the University Endowment Lands almost directly opposite the UBC campus and plainly visible from Wreck Beach below.

The proximity to the airport gives the place its particular texture. Widebodies come over low and constant, landing gear down, and the noise arrives in waves that the sandpipers ignore entirely. Beyond the jetties the delta opens west into the strait, with the North Shore mountains standing behind Vancouver to the northeast and, on a clear day, Mount Baker off to the southeast. Iona Beach itself is a long gravel and driftwood shore that gets a steady traffic of dog walkers and cyclists who have no idea they are sharing it with birds that flew in from Siberia. Nobody designed this. A city built a place to process its waste, a river kept building land, and a continent's worth of migratory birds decided the result was exactly what they needed.