The red knot is a medium-sized shorebird that undertakes one of the longest migrations in the animal kingdom. These birds breed in the Canadian Arctic and northern Greenland and winter in parts of South America and the Southeastern United States. They are known for their lengthy nonstop migrations of up to 9,300 miles between their breeding and wintering grounds.
In recent decades, the red knot has faced several threats that have caused significant declines in its population. Conservationists have raised alarms about the future of this migratory species and whether it can recover from its depleted numbers. This article will explore the major threats facing red knots, analyze population trends and conservation statuses, and assess whether this iconic bird is endangered.
What is the red knot?
The red knot (Calidris canutus) is a bulky sandpiper distinguished by its reddish underparts during the breeding season. It measures 8-10 inches in length with a wingspan around 20 inches. Outside of the breeding season, its plumage fades to a gray above and white below. Its straight dark bill tapers to a point for probing wet sand for mollusks, worms, and crustaceans.
This migratory species uses its powerful wings and robust body stores to travel thousands of miles between its Arctic breeding grounds and wintering areas along the coasts of North and South America, Europe, and Africa. Scientists recognize six subspecies across this broad range, three of which occur in North America: the rufa, roselaari, and islandica red knots.
Where does the red knot live?
During the spring and summer months between late May and early August, red knots nest in dry tundra habitats across the Canadian Arctic and Greenland. The birds gather in large breeding concentrations along the west coast of Hudson Bay and on islands in the eastern Canadian Arctic.
By late July, red knots depart the Arctic on their southern migration routes. Different populations winter in specific regions across the Americas based on their subspecies and breeding origins. The rufa red knots, also called American red knots, primarily winter along the Atlantic coast from Massachusetts to Florida and down through the Caribbean to Patagonia. The islandica red knots mainly winter in Western Europe from the UK to France. Meanwhile, the roselaari red knots winter along the Pacific Coast from California to Chile.
During migration, red knots rely on key staging and stopover sites to rest and refuel. Delaware Bay along the Northeastern US coast is the most important spring migration stopover area, where the birds double their weight on horseshoe crab eggs in preparation for their nonstop flight to the Arctic.
What threats face the red knot?
The red knot faces a combination of threats across its breeding, migratory, and wintering range. The major factors believed to be contributing to red knot declines include:
Decreased food availability
– Overharvesting of horseshoe crabs in Delaware Bay, a crucial spring staging site, has drastically reduced the crab egg food source the birds rely on to quickly gain weight before completing migration.
– Climate change and human disturbances are altering food chains and availability in Arctic ecosystems where red knots breed.
– Loss of wetlands and coastal habitats along migration routes and wintering areas decreases food resources and stopover habitat.
Habitat degradation
– Development, shoreline armoring, and pollution have degraded critical coastal ecosystems and shellfish beds red knots depend on for food.
– Sea level rise attributable to climate change threatens loss of optimal coastal habitats.
Human disturbance
– Birdwatchers and photographers approaching and flushing huge concentrations of birds may interfere with feeding and resting time.
– Off-road vehicles and recreational activities can degrade fragile habitats.
Predation risks
– The rapid growth of certain predators like peregrine falcons may exert unsustainable pressure on red knot populations.
What evidence shows red knot populations are declining?
Scientific surveys of red knots across their flyways over the past few decades reveal significant declines that have raised conservation concerns:
Rufa red knot
– The rufa subspecies that migrates along the Atlantic Coast has faced the steepest declines. Surveys estimate a population drop from around 100,000-150,000 birds in the 1980s to a low of around 15,000 by 2006.
– Counts at key wintering and migratory sites like Tierra del Fuego, Chile, Delaware Bay, and Florida similarly show declines of 50% to 75%.
Islandica red knot
– Breeding surveys in Greenland indicate a 50% decrease in islandica red knots from around 34,000 birds in the 1970s to only 15,000 by 2010.
– Winter population counts in Western Europe declined 43% during the same period.
Roselaari red knot
– Evidence suggests roselaari red knots along the Pacific Coast may have experienced low-level declines, although data is limited. Surveys estimate around 15,000 birds.
| Subspecies | Population in 1980s | Low point | Current population |
|---|---|---|---|
| Rufa | 100,000-150,000 | 15,000 in 2006 | 30,000-40,000 |
| Islandica | 34,000 in 1970s | 15,000 in 2010 | 19,000-20,000 |
| Roselaari | Unknown | Unknown | 15,000 |
What conservation statuses and protections apply to the red knot?
Given the data showing significant population declines, various conservation organizations and governments have designated the red knot as an at-risk or threatened species:
United States
– The rufa red knot was federally listed as Threatened under the Endangered Species Act in 2014 due to loss of habitat and food sources along its migration route.
– It is listed as Endangered, Threatened, or a Species of Special Concern in many Northeastern states along the Atlantic flyway.
Canada
– The Committee on the Status of Endangered Wildlife in Canada assessed the rufa knot as Endangered and the islandica knot as Special Concern in 2007.
International
– The International Union for Conservation of Nature (IUCN) Red List categorizes the rufa knot as Near Threatened and the islandica knot as Endangered.
– The red knot is listed under the Convention on Migratory Species and protected under regional agreements on southern South American and African-Eurasian migratory waterbirds.
What conservation efforts aim to protect the red knot?
Many initiatives across the red knot’s range seek to monitor, manage, and protect populations and habitats:
Surveying and banding
– Extensive capture and banding programs track migrations, identify key sites and threats, and estimate survival rates.
Habitat protection
– Sites like Delaware Bay, Yellow Sea shores, Banc d’Arguin in Africa, and Tierra del Fuego in South America are now protected as shorebird reserves.
– Wetland restoration and shoreline management expand habitat.
Hunting restrictions
– Bans or limits on hunting red knots in Caribbean wintering areas reduce this pressure.
Horseshoe crab harvest limits
– Restrictions on overharvest help recover crab egg food supplies in Delaware Bay.
Outreach
– Programs enlist and educate fishermen, students, birdwatchers, and communities to support red knot conservation.
Conclusion
In summary, substantial evidence indicates that red knot populations across subspecies have declined over the past 40 years, with the rufa knot of the Atlantic Coast facing the most severe drops. The main threats contributing to the red knot’s vulnerable status include habitat loss, poor food availability, human disturbances, and predation along its migratory flyways. While conservation efforts to track, protect, and manage ecosystems and human activities have expanded, the species remains threatened.
Ongoing monitoring and habitat initiatives focused on stabilizing key sites like Delaware Bay and Arctic breeding grounds will be important for the red knot’s future. But the effects of climate change and other long-term ecosystem shifts will likely require adaptable conservation policies to support resilient red knot populations. Only through sustained international collaboration addressing threats across the red knot’s range can this migratory bird be secured for the future as issuues from the impacts of climate change and human activities persist. While not yet endangered, focused conservation attention and support are still needed to stabilize and recover red knot populations facing an uncertain future.
References
Baker, A. J., González, P. M., Piersma, T., Niles, L. J., de Lima Serrano do Nascimento, I., Atkinson, P. W., … & Morrison, R. I. (2004). Rapid population decline in red knots: fitness consequences of decreased refuelling rates and late arrival in Delaware Bay. Proceedings of the Royal Society of London. Series B: Biological Sciences, 271(1541), 875-882.
Piersma, T., Rogers, D. I., González, P. M., Zwarts, L., Niles, L. J., de Lima Serrano do Nascimento, I., … & Aarts, G. (2005). Fuel storage rates before northward flights in red knots worldwide: facing the severest ecological constraint in tropical intertidal environments?. Behavioral Ecology and Sociobiology, 57(2), 215-229.
US Fish & Wildlife Service. (2014). Rufa Red Knot Background Information and Threats Assessment. Supplement to Endangered and Threatened Wildlife and Plants; Final Threatened Status for the Rufa Red Knot (Calidris canutus rufa) [Docket No. FWS–R5–ES–2013–0097; RIN AY17].
International Wader Study Group (2016). Red Knots – Status, Threats and Conservation Recommendations. Report to the 12th Meeting of the Conference of the Parties to the Convention on the Conservation of Migratory Species of Wild Animals.
Watts, B.D. (2020). Status and Trends of Red Knots in the Western Hemisphere with Recommendations for Monitoring, Research, Outreach, and Conservation. The Center for Conservation Biology Technical Report Series. CCBTR-20-03. College of William & Mary/Virginia Commonwealth University.
