Pacific Flyway: Calidris canutus roselaari
Biologists estimate that one third of the C.c. roselaari population spends the non-breeding season on the Pacific coast of Baja California, in bays protected from further development by the presence of industrial salt mines. Some juvenile birds remain in coastal estuaries of the northern Sea of Cortez for their first year, as they await breeding maturity at two years old.
Little is known about the migration sites of a relatively small population that travels along the Pacific coast of the Americas. Willapa Bay and Grays Harbor on the Washington Coast is the major stopover on the northern migration to the Alaskan coast and Wrangell Island. Flocks migrate southward from Eastern Asia and Alaska along the Pacific Coast to winter in Baja California and the Caribbean.
Western Atlantic Flyway: Calidris canutus rufa
C.c. rufa spends most of the year in the remote bays of Tierra del Fuego, an archipelago off the southernmost tip of South America. It begins its northern migration with stops in Argentina and Brazil before crossing the Caribbean to the Atlantic shoreline of the United States. Migration timing is coordinated with the spawning season of Horseshoe Crabs at Delaware Bay, whose eggs are the critical energy source for completing the migration. For successful breeding, the timing of tundra insect hatches is similarly critical. Birds gather at the southern end of Hudson Bay for the southern migration, then follow the Atlantic Coastline back to Tierra del Fuego.
Concerted efforts by conservationists to protect Horseshoe Crabs, to reduce hunting of shorebirds, and to educate the public about these remarkable beings help create conditions for their continued survival.
Icelandic Flyway: Calidris canutus islandica
C.c. islandica crisscrosses the North Atlantic, spending most of the year on the European coasts of the North and Wadden Seas. This subspecies then migrates to breeding grounds on Ellesmere Island in the Canadian Arctic and the northern coast of Greenland, with important stopover sites on the coasts of Norway and Iceland.
Viking legends describe mariners following migrating birds to and from Iceland. Recent radio tracking has been able to show variations in an individual bird’s flight routes from one year to the next. Correlating this data with meteorological and climate data may give scientists more insights into why routes change, and how species may adapt to climate change.
Eastern Atlantic Flyway: Calidris canutus canutus
Only a small percentage of the C.c. canutus population migrate as far as South Africa. Larger populations use the important conservation areas of the Banc d'Arguin National Park of Mauritania and the Bijagós Archipelago of Guinea-Bissau.
On their northern migration, some flocks follow the eastern Atlantic coastline, while others cross the Saharan Desert before stopping to refuel on the coastal mudflats of Tunisia. The next jump on the route is across the Mediterranean and Europe to refuel in the Wadden Sea, an intertidal zone of the North Sea, before the final flight to the tundra breeding grounds. This Red Knot’s southern migration route extends from the Taymyr Peninsula in western Siberia southward through Europe to the western coast of Africa.
East Asian-Australasian Flyway:
Calidris canutus piersmai and C.c. rogersi
The migration system of the East Asian-Australasian Flyway can be visualized as an hour glass with the constricted neck centered on the Yellow Sea region of Asia, particularly on Bohai Bay in China.
Two subspecies of Red Knots funnel through Bohai Bay on their northward migration: C.c. piersmai and C.c. rogersi. Birds spend three to four weeks during April and May staging in the area to acquire energy for migration and breeding before fanning out to nesting areas in the Siberian Arctic. Most individuals of the slightly smaller subspecies, C.c. piersmai (green track), breed on the New Siberian Islands off the northern coast of Russia and spend the non-breeding season (September-April), on the coast of North West Australia. Most C.c. rogersi (light purple track), breed in Chukotka Peninsula of NE Russia and spend the non-breeding season on coasts of eastern Australia and New Zealand.
Staging birds require sufficient food and undisturbed resting areas, called roosts, so that they can arrive on breeding areas in top condition for successful nesting and brood-rearing. Thus, the staging habitat at Bohai Bay is an essential link in the chain of sites used by Red Knots each year in this Flyway.
Sadly, in Bohai Bay, shorebird habitat is literally vanishing in front of our eyes. Reclamation of intertidal flats for industrial uses, pollution, and increased disturbances to land and water flow along the shoreline are all contributing to habitat loss. Conservationists and scientists are very concerned that Red Knots will not be able to adapt quickly enough, or find alternative staging areas soon enough, before this loss of shorebird habitats takes its toll. Current field studies show marked declines in population size and survival rates of Red Knots in the East Asian-Australasian Flyway.