72 Microseasons of the Pacific Northwest

Dunlin (Calidris alpina) are the most abundant wintering shorebird on the Pacific Coast, and by late October enormous flocks have assembled in the region's major estuaries. These compact, rusty-backed shorebirds nest on Arctic tundra in summer, but from October through April the tidal flats of Grays Harbor, Willapa Bay, the Columbia River Estuary, Padilla Bay, and Boundary Bay (BC) host thousands to tens of thousands of birds. Individual flocks of 5,000 to 20,000 dunlin are not unusual at these sites. What makes dunlin truly remarkable is their aerial display. When a peregrine falcon or merlin hunts the flock, the birds respond with synchronized "murmurations" — tight, coordinated masses that twist, contract, and expand in a fluid display that has been compared to the European starling murmurations but with a uniquely flickering quality. As the flock rolls, the gray-brown backs and white bellies alternate, creating silvery flashes visible from a great distance. Grays Harbor National Wildlife Refuge, Bottle Beach State Park, and the Nisqually National Wildlife Refuge all offer reliable dunlin viewing from the dike trails. At low tide, dunlin probe the mud with their drooped-tipped bills, hunting tiny invertebrates in the top centimeters of sediment. At high tide they compress onto the upper marsh and beach edges, roosting in dense masses. The sheer numbers — and the drama of the falcon-chased aerial displays — make dunlin one of the most visually spectacular wildlife events of the Pacific Northwest autumn, yet they go largely unnoticed by non-birders. Alongside dunlin on these flats are western sandpipers, dowitchers, black-bellied plovers, and dunlin-sized flocks of western sandpipers heading farther south.