The red knot is a medium-sized shorebird that makes one of the longest yearly migrations of any bird species. Every year, red knots undertake an arduous journey from their breeding grounds in the Canadian Arctic to wintering grounds as far south as Tierra del Fuego at the southern tip of South America. This annual trip can cover over 18,000 miles (29,000 km) roundtrip!
What are red knots?
Red knots (Calidris canutus) are robin-sized shorebirds that breed in the Arctic during the summer months. Their breeding plumage features distinctive reddish feathers on their head, breast, and belly. The rest of their body is mottled grey and brown. During the winter, red knots molt into a dull grey winter plumage. They have a stout black bill and long black legs suited for foraging along muddy shorelines.
There are 6 subspecies of red knots that can be found wintering and migrating along the coasts of North and South America, Europe, Africa, Asia, and Australia. The subspecies C. c. rufa makes the longest migration from the Canadian Arctic to Tierra del Fuego.
Why do red knots migrate such long distances?
Red knots undergo some of the longest migrations in the animal kingdom for a few key reasons:
- To reach optimal breeding grounds – Red knots breed in the High Arctic during the summer when abundant food and long daylight hours allow them to raise their young. The Arctic provides ideal breeding conditions that don’t exist farther south.
- To reach optimal wintering grounds – Red knots winter in areas with expansive coastal mudflats and lagoons rich in mollusks, crustaceans, and marine worms. These prey resources are not available in the Arctic during winter.
- To follow food availability – Red knots time their migration to take advantage of seasonal peaks in food availability along their migratory route. This allows them to refuel and continue their journey.
What is their migratory route?
The full migratory route of rufa red knots spans from the Canadian Arctic all the way down to the southern tip of South America:
- Breeding grounds: High Arctic islands like Ellesmere, Axel Heiberg, and Svalbard
- Spring staging areas: Coastal areas of Hudson Bay, James Bay, and the Mingan Archipelago in eastern Canada
- Primary wintering grounds: Coastal areas of Tierra del Fuego at the southern tip of Argentina and Chile
- Migration stopover sites: Coastal wetlands along the Atlantic and Gulf coasts of North America and northeastern South America
The birds follow major flyways over land and sea, stopping to rest and feed along the coasts of North and South America. Their route takes advantage of key food resources available during their biannual travels between the Arctic and sub-Antarctic regions.
How far do they travel each way?
The total distance traveled by rufa red knots on their annual roundtrip migration is estimated to be around 18,000 – 20,000 miles (29,000 – 32,000 km). Here is a breakdown of the distances covered in each direction:
Northbound migration (Tierra del Fuego to Arctic breeding grounds)
- Tierra del Fuego to Maranhão, Brazil: ~5,500 miles (9,000 km)
- Maranhão to Mingan Archipelago, Quebec: ~4,000 miles (6,500 km)
- Mingan Archipelago to Arctic breeding grounds: ~2,500 miles (4,000 km)
- Total distance: ~12,000 miles (19,000 km)
Southbound migration (Arctic breeding grounds to Tierra del Fuego)
- Arctic breeding grounds to James Bay, Ontario: ~2,500 miles (4,000 km)
- James Bay to Maranhão, Brazil: ~4,000 miles (6,500 km)
- Maranhão to Tierra del Fuego: ~5,500 miles (9,000 km)
- Total distance: ~12,000 miles (19,000 km)
By traveling between the extreme northern and southern hemispheres, these marathon migrants log an incredible 18,000 to 20,000 miles during their annual migration!
How long does the migration take?
Red knots’ migration is a feat of endurance that unfolds over the course of 6-8 months each year. Here is an overview of the migration timeline:
Timeframe | Migration Stage |
---|---|
Early May | Depart Tierra del Fuego for Arctic breeding grounds |
Late May – Early June | Staging in Maranhão, Brazil to refuel |
Mid June | Arrive at breeding grounds in Canadian Arctic |
July – August | Nesting and rearing young on Arctic breeding grounds |
September | Fall migration starts south from the Arctic |
October – November | Staging along the Atlantic coast of North America |
December – February | Wintering in Tierra del Fuego |
The birds spend about 1-2 months on their Arctic breeding grounds in the summer. The rest of the year is spent on migration and wintering. Their migration lasts over 6 months each way, for a total roundtrip of 8-9 months.
How do they fly such long distances?
Red knots are specially adapted to undertake their incredibly long migrations each year through the following key attributes and strategies:
- Ultra-efficient wing design – Long, pointed wings provide excellent aerodynamics and energy efficiency in flight.
- High fat reserves – Red knots build up fat reserves equal to 50-100% of their body weight to fuel migration.
- Frequent refueling – Stopovers along the migration route allow red knots to rest and rapidly regain fat stores.
- Strong flight muscles – Highly adapted pectoral muscles allow red knots to fly nonstop for thousands of miles over barriers like the Atlantic Ocean.
- Internal compass – Red knots use magnetic fields and celestial cues to navigate with precision between Arctic and sub-Antarctic regions.
These adaptations enable red knots to achieve one of the animal kingdom’s most extreme long-distance migrations year after year.
Threats faced during migration
Red knots face many threats and challenges during their grueling annual migration cycles. Some major threats include:
- Loss of staging and wintering habitats to coastal development
- Reduced food availability at refueling stops due to overharvesting and climate change
- Disturbance by humans, vehicles, and pets near key coastal habitats
- Oil spills and pollution
- Extreme weather events and storms
- Predation by falcons, gulls, foxes, and other animals
These threats compound the immense physical challenges of the knots’ migration and have contributed to declines in red knot populations in recent decades. Conservation efforts are aimed at protecting critical habitats and mitigating threats along their flyways.
Impact of climate change
Climate change could seriously impact red knots’ migratory patterns and survival in several ways:
- Shifts in food availability and timing along migration route
- Mismatch between arrival time and peak food abundance in the Arctic
- Increased frequency and severity of storms
- Sea level rise flooding coastal habitats
- Changing wind patterns affecting migration routes and energy costs
- Increased heat stress and water loss during migration
By affecting Arctic ecosystems and weather patterns, climate change could make red knots’ extreme migrations even more difficult. Conservation efforts will need to protect habitat and reduce other threats to help offset the emerging challenges posed by climate change.
Tracking their migration
Scientists track red knots’ migratory journeys using several important methods:
- Leg bands – Engraved bands placed around red knots’ legs allow individual identification when birds are recaptured or resighted.
- Radio transmitters – Miniature radio tags can track red knots’ precise migratory routes, timing, and habitat use.
- Geolocators – Light level geolocator devices record daily locations when recovered after migration.
- Genetic analyses – DNA analysis can identify genetic differences between breeding, wintering and stopover populations.
- Stable isotope analysis – Isotopic signatures in feathers can provide clues about migration distance, route, and timing.
By combining these techniques, scientists are gaining detailed insight into the phenomenal odyssey red knots undertake each year between the Arctic and southern South America.
Importance of protecting red knots
It is critical to protect red knots because:
- They are an iconic and inspiring example of animal endurance, navigation, and survival.
- They connect ecosystems across continents during migrations between hemispheres.
- They are indicators of the health of coastal wetland habitats along flyways.
- They have experienced serious population declines in recent decades.
- They face escalating threats from human activities and climate change.
By supporting international conservation efforts, protecting crucial coastal habitats, and reducing disturbances, we can ensure this legendary migrant continues its extraordinary journeys for generations to come.
Conclusion
The epic migrations undertaken by red knots are one of the natural world’s most astonishing feats of endurance. By traveling up to 20,000 miles annually between Arctic and sub-Antarctic regions, red knots complete one of the longest migrations of any animal on earth. Their nonstop flights push the boundaries of physiology and navigation. Sadly, red knots now face escalating threats along their migratory flyways from human activity and climate change. Protecting these tough and tenacious birds by conserving coastal habitats and reducing disturbances will be crucial to preserving their amazing journeys for the future.