Red Knot (Calidris canutus) lives in arctic tundra and coastal mudflat across Circumpolar Arctic to southern hemisphere. Its conservation status is Near Threatened.
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Some red knots fly farther than a cross-continent road trip, covering more than 14,000 km (9,000 mi) from the Arctic to the tip of South America and then back again each year. One individual ringed as a first-winter bird in October 1978 was seen alive again in February 2006, a span of 27 years, 3 months, and 29 days, showing how long these medium-sized shorebirds can live. Another tagged "B95" was at least 20 years old when last recorded in 2014, underscoring the species' remarkable longevity for its size.
Before the epic migration, a red knot can double its body mass, swelling from the typical 100-200 g range. To make room for this fuel, the bird shrinks its stomach and gizzard, then rebuilds a thicker gizzard in just six days when it switches to harder foods on winter grounds. These rapid organ adjustments let the bird store enough fat, increasing fat mass by more than 50 percent.
At Delaware Bay, red knots time their spring stopover to the massive spawning of horseshoe crabs, feasting on the eggs that fuel 50 to 80 percent of the migrating rufa population each year. The birds arrive extremely thin, then double their weight over a 10-14-day stay as they gorge on the nutrient-rich eggs.
Genetic studies show the oldest red-knot lineage, C. c. canutus, split from its relatives about 20,000 years ago (95 % CI: 60,000-4,000 years). Later, the American and Siberian breeding groups diverged roughly 12,000 years ago (95 % CI: 45,000-3,500 years), illustrating how glacial cycles carved distinct subspecies that now span from the high Arctic to tropical coasts.
The red knot occupies a massive global range of 100,000-1,000,000 km² (39,000-386,000 sq mi) and supports a world population of roughly 1.1 million birds. Though listed as near-threatened worldwide, its sheer numbers and extensive habitat use keep it off the IUCN's decline thresholds, highlighting the importance of protecting key stopover sites to maintain this large migratory flock.
Sources
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As the tide recedes, a flock of Red Knots sweeps across the exposed mudflats, their cinnamon-hued plumage glistening like embers in the fading light. With a fluid, stop-and-start gait, they dance through the shallows, probing the sediment with their sensitive bills for the hidden treasures of small crustaceans and mollusks. In their epic migrations, these birds embody a testament to endurance, bridging the vast expanses between their Arctic breeding grounds and southern wintering habitats with a resilience that is both captivating and precarious.
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