The Pacific Flyway is the path that migratory birds follow along the Pacific Coast during their annual migrations. Millions of shorebirds and waterfowl travel between northern breeding grounds and southern wintering sites. The Pacific Flyway originates in Western Alaska, around the Yukon River Delta.
Some birds come from as far as Siberia in the Soviet Union.
The Pacific Flyway consists of several parallel routes. Wetlands and coastal bays are stop-over sites for resting and feeding. If these birds could not eat and rest in wetlands, they would not have the energy needed to complete their migration and they could die. Many of the migratory birds in Sweetwater Marsh feed in estuarine channels and saltwater ponds. More of them forage in sandflats and mudflats than on mudbanks, beach, or salt marsh areas.