Red Knots are medium-sized sandpipers and a migratory wonder
Calidris canutus spends most of the year in temperate and tropical coastal areas of Africa, South America and Oceania, then travels halfway around the world to Arctic Circle tundra sites to breed. Like most Arctic migrants, this annual journey allows Red Knots to take advantage of the seasonally ephemeral, but amazingly abundant, nesting habitats and food resources in the Arctic. It also lets them spend the non-breeding months in more benign regions, where they can expend less energy while resting, growing fresh feathers (molting), and preparing for the next migration.
Red Knots are able to change color, change the size and weight of internal organs, and make multiday non-stop flights covering thousands of miles. They pay attention to the phases of the moon, the tides, the position of sun and stars, the altitudes and directions of storms, and to the magnetic field of the earth. They time their migration to coincide with the breeding cycles of marine and terrestrial invertebrates on the other side of the globe. Red Knot hatchlings emerge from eggs covered in down, able to feed themselves and walk. Because their parents will have already left the Arctic before them, once the young birds are able to fly, they find their way back to the southern non-breeding grounds without adult guidance.
The Red Knots' choice to commit a huge output of energy to this globe-spanning migration is made with the expectation of access to food resources along the way and at the destination. Specific refueling sites where birds can rest and find food en route are crucial. If seasonal timetables are off, or if expected foraging sites have been developed for human uses, the consequences may be disastrous.
Red Knot Subspecies
As the Arctic landscape changed following the last Ice Age, the breeding ranges of Red Knots became separated. Gradually over time, differences in size and coloration from one group of birds to the next resulted in the evolution of the six subspecies known today.
The ancestral group C.c. canutus, continues to migrate from the Taymyr Peninsula of Russia, through northern Europe to the west coast of Africa. Those who migrated down the Pacific coast of Asia eventually became C.c. rogersi and C.c. piersmai. Some birds began to use the adjacent Arctic lands of Alaska and then Canada. The American continents now separate the group migrating down the Pacific coast of the Americas, C.c. roselaari, and the group that flies to Tierra del Fuego along the Atlantic coast, C.c. rufa. Finally, some bird populations of eastern Canada and Greenland began to migrate east to Europe for their non-breeding season. These birds constitute the youngest subspecies C.c. islandica.
Evolution, the painting above, evokes a decorated hide of the reindeer herding peoples of the Russian Arctic to 'map' the migration routes of the six Red Knot subspecies. Reindeer hide clothing is decorated with bands of embroidered cloth on the seams and edges. Complex, mirror image designs repeat along the bands. The map of the migration routes reads counterclockwise from the lower left of the painting. The Arctic is in the center. The lower brown triangle represents the Eurasian, African, and Australian continents; the upper represents the American continents. The white triangles are the Atlantic and Pacific Oceans. Pictograph drawings represent birds flying up the coast. Drawings in the center of the continents represent ancient but now little used interior flyways. *Click on painting image for a larger lightbox view.