The red knot is a medium-sized shorebird that migrates huge distances every year from breeding grounds in the Arctic to wintering grounds as far south as Tierra del Fuego. Unfortunately, the red knot is facing several threats that are causing severe declines in its population. In this article, we’ll look at what exactly the red knot is, why it migrates such long distances, and what the major threats are that are putting it at risk.
What is the red knot?
The red knot (Calidris canutus) is a stocky sandpiper in the Scolopacidae family. It measures about 9-11 inches in length and weighs 2.4 to 5.3 oz. During breeding season, the red knot sports a reddish breast and face. In winter, its plumage is a more nondescript gray. The red knot has a straight black bill and long black legs.
There are six recognized subspecies of the red knot:
- C. c. canutus breeds in Siberia and winters in western Europe and western Africa.
- C. c. islandica breeds in the Canadian Arctic and winters in western Europe.
- C. c. piersmai breeds in the New Siberian Islands and winters in northwest Australia.
- C. c. rogersi breeds in Alaska and winters along the coasts of the Americas.
- C. c. roselaari breeds in Wrangel Island and winters along the coasts of the Americas.
- C. c. rufa breeds in the central Canadian Arctic and winters in Tierra del Fuego at the southern tip of South America.
The red knot inhabits tundra and wetland habitats, both inland and along coasts. During migration, it stops over at coastal habitats like tidal mudflats and sandy beaches. Here, it uses its long bill to probe into wet sand or mud to find small invertebrates like crustaceans, mollusks, and marine worms to eat.
Why does the red knot migrate such long distances?
The red knot is one of our planet’s champion migrators. Some populations migrate over 9,000 miles between their Arctic breeding grounds and wintering grounds in South America. This extreme migratory behavior is driven by the red knot’s specialized lifestyle.
The red knot times its migration to coincide with ideal conditions at each destination. It departs the Arctic in early summer after breeding and heads south to take advantage of the glut of food available at stopover sites with milder weather. By winter, it reaches sites like the Georgia coast, the Gulf of Mexico, Brazil, and Argentina where food is plentiful.
In spring, the red knots leave their wintering grounds to begin the long journey back to the Arctic. They follow an interior route through North America’s Great Plains where snowmelt produces ideal stopover habitat. Arriving back on the Arctic tundra in early June, they take advantage of the surge of insect life, abundant food for the chicks they will soon produce. The red knot’s migratory strategy allows it to exploit these seasonal peaks in food availability.
What are the major threats facing the red knot?
Several key threats have led to substantial declines in red knot populations over the past few decades:
Habitat loss at migration stopovers
Red knots rely on key stopover sites to rest and refuel during their marathon migrations. Habitat loss at these sites from threats like coastal development, shoreline armoring, and human disturbance has reduced food availability and ability to rest, causing declines in migration survival.
Stopover Site | Region | Habitat Threats |
---|---|---|
Yellow Sea, China | East Asia | Land reclamation |
San Antonio Oeste, Argentina | South America | Commercial development |
Delaware Bay, New Jersey | East Coast U.S. | Beach erosion, shoreline armoring |
Decreased food availability
At many wintering and stopover sites, declines in populations of the red knot’s main food sources like horseshoe crab eggs, clams, and snails have made it harder for the birds to achieve adequate weight gain. This causes lower breeding success and survival. Causes include overharvesting of horseshoe crabs, shellfish, and other prey species.
Climate change
The effects of climate change like sea level rise, increasing storm frequency and severity, and asynchronously shifting bird and prey migrations have disrupted the red knot’s access to food resources. In the Arctic, warmer temperatures have caused declines in insect food sources for chicks. Climate change will likely continue to alter habitat and exacerbate other threats.
Conclusion
The red knot’s incredible migratory life cycle puts it at risk from threats all across its range. Habitat loss at migration stopovers, declining food availability, and climate change impacts have caused sharp declines in red knot populations, with some dropping by 75% in the past few decades. Conservation efforts focused on preserving stopover and wintering habitats, monitoring prey food sources, and reducing other threats are underway to stabilize populations. But the red knot remains vulnerable, especially as climate change gains momentum in the coming years. Protecting this champion traveler will require coordinated habitat management and reductions in greenhouse gas emissions worldwide.