The red knot is a medium-sized shorebird that breeds in the Arctic and undertakes one of the longest migrations in the animal kingdom. Some populations migrate from breeding grounds as far north as the Canadian Arctic all the way to Tierra del Fuego at the southern tip of South America – a round trip of over 18,000 miles!
Red knots are truly impressive birds. Here are some cool facts about these world travelers:
Extremely long migrations
As mentioned above, some red knot populations migrate astonishing distances every year. For example, red knots breeding in the central Canadian Arctic fly roughly 9,300 miles to wintering grounds in Tierra del Fuego. After wintering at these southern latitudes, they make the return trip back to the Arctic to breed. This 18,600 mile round trip migration is one of the longest of any bird species.
Not all red knot populations migrate quite as far. Breeding populations in more temperate northern latitudes, like Northern Europe, may only migrate as far south as West Africa for the winter. But even these “shorter” migrations of 5,000-6,000 miles are incredibly impressive for a medium-sized shorebird.
The red knot’s ability to fly such extreme distances relies on storing up large fat reserves to fuel their flight. Prior to migration, red knots go through a period of intense feeding to fatten up. This allows them to fly long distances of over 1,500 miles without stopping!
Rapid long-distance flights
In addition to flying incredibly long distances, red knots also make these journeys very rapidly. The birds time their migration to make use of favorable winds patterns. However, they have still been recorded flying at average speeds exceeding 150 miles per day during migration.
Some individual red knots have been documented making even more spectacular non-stop flights. One red knot fitted with a radio tag flew an astonishing 2,485 miles non-stop from northern Canada to the southeastern United States in just over 4 days. That equals an average of at least 620 miles flown per day!
Annual migration “races”
The red knot’s rapid migration capabilities are highlighted each May in one of the most amazing natural spectacles – the annual migration “race” that takes place along the shores of Delaware Bay.
Delaware Bay is a key refueling stopover point for red knots. Each May, hundreds of thousands of knots congregate there to feast on an abundant food source – horseshoe crab eggs – to fuel up for the final leg of migration to the Arctic.
The birds time their arrival to coincide with the horseshoe crabs’ spawning period. However, the crabs’ egg laying activity only lasts about two weeks. This sets up an intense period where the birds hurry to the Bay en masse and frantically gorge themselves to accumulate enough fat reserves before the crab eggs are gone.
Some radio-tagged birds have been tracked flying up to 360 miles per day to reach the Bay in time for this event! It’s an impressive example of the red knot’s ability to perform rapid, long-distance travel when needed.
Resilience and adaptability
One of the main reasons red knots can achieve such migratory feats is their resilience and ability to adapt to changing conditions. Red knots have evolved the ability to rapidly alter their physiology and behavior in response to changing food supplies, weather conditions, and other factors.
This adaptability allows them to take advantage of temporary abundant food sources to fuel up for migration. It also helps them respond to shifting climatic conditions year to year. For example, red knots are able to advance or delay their migration timing by up to two weeks to match the conditions at stopover sites.
Red knots even show resilience when facing tremendous ecological challenges. Some populations that were decimated by overhunting and habitat loss have rebounded after conservation measures were put in place. The ability to rebound under adverse conditions makes red knots one of the hardiest shorebird species.
Unique Characteristics of Red Knots
In addition to their amazingly long migrations, red knots have many other fascinating and unique characteristics about their biology and behavior.
Breeding and nesting
Red knots breed in the Arctic tundra of the far north. They scratch out small depressions in the ground which form their very minimalist nests.
Nests usually consist of just a shallow dirt cup, lined with little vegetation and feathers. The eggs and chicks are very well camouflaged against predators thanks to their speckled brown, tan, and grey plumage.
Red knots exhibit one of the shortest incubation periods of any bird, with eggs hatching after just 22 days. Once hatched, the chicks feed themselves and leave the nest within hours.
Molting
Red knots go through a complete molt of their plumage each year prior to migration. This molt includes all their flight feathers, meaning the birds are flightless for several weeks.
Prior to molting, the birds double their weight by building up fat reserves. This allows them to remain active foraging for food on the ground while they wait for new flight feathers to regrow.
Different red knot populations adhere to different molting strategies based on their migratory distance. Long-distance migrants molt at stopover sites farther south, while short distance migrants molt closer to Arctic breeding areas.
Knotting together in large flocks
One of the keys to the red knot’s survival is its tendency to form large flocks, especially during migration. Banding together provides safety in numbers and allows the birds to better take advantage of temporary food bonanzas.
These large aggregations give rise to the origin of the bird’s name – knots or knouts referring to a group or knot of people. When arriving en masse at stopover sites, the swirling flocks of red knots can number in the tens or even hundreds of thousands of individuals.
Unique bill shape
The red knot has a distinct bill shape compared to other shorebirds. Their short, straight bill tapers slightly at the tip. This shape is adapted for picking small food items off the surface of sand or mud.
Their bill allows them to expertly pluck tiny seeds, aquatic invertebrates, and eggs off the substrate. The tip of the bill is sensitive enough to detect prey buried under the surface via touch and vibration.
Diet and Feeding Habits
Red knots are very versatile foragers, able to exploit a wide variety of food sources depending on habitat and time of year. Their diverse diet helps fuel their energy needs for migration.
On the breeding grounds
During the breeding season in the Arctic tundra, red knots feed mainly on insects and other small invertebrates. Their short bills allow them to pick tiny spiders, larvae, and eggs from the surface of the ground and vegetation.
Common foods include beetles, flies, midges, leafhoppers, moth eggs, and spiders. Red knots may also consume small berries and seeds.
On migration
When stopping over on migration, red knots take advantage of whatever abundant food sources they can find along the coasts and inland wetlands. They gorge on foods like shrimp, marine worms, mollusks, fish eggs, and small crab eggs when available.
At Delaware Bay, the migrating birds focus intensively on one food source – the eggs of spawning horseshoe crabs. This super abundant source of fat and protein allows the birds to nearly double their weight in two weeks or less.
On the wintering grounds
During the non-breeding season at southern latitudes, red knots continue to forage along marine coasts. They scour intertidal zones, beaches, and mudflats for small invertebrates.
Common winter foods include marine worms, mollusks, small clams or mussels, crustaceans, and insect larvae. Occasionally they may eat algae, seeds, or even sewage.
Habitat and Range
The red knot has an extremely broad range and utilizes a variety of habitats throughout its migratory cycle. Their range spans from the high Arctic down to the southern tip of South America.
Breeding grounds
Red knots nest in the dry, treeless tundra habitats of the far north. They are found breeding across northern parts of Alaska, Canada, Greenland, Scandinavia, and Russia.
Within the tundra ecosystem, red knots tend to nest near small ponds, streams, or coastal areas. This provides access to food sources like insects and berries.
Migration stopover habitats
During migration, red knots rely on many key stopover sites to rest and refuel. Important habitats include coastal wetlands, mudflats, sandy beaches, and inland lakes/ponds.
Some well-known migratory stopover sites include Delaware Bay, the Yellow Sea coast of China, San Antonio Oeste in Argentina, and Banc d’Arguin in Mauritania.
Wintering grounds
Red knots winter along both the Atlantic and Pacific coasts of the Americas. On the east coast, they are found as far south as Tierra del Fuego at the southern tip of Chile and Argentina.
On the west coast, they winter from California and Mexico south to northwest Peru and the Galapagos Islands. They frequent coastal wetland and intertidal habitats while wintering.
Conservation Status and Threats
Some populations of red knots are under threat due to habitat loss and overharvesting of food sources along migratory routes. Conservation efforts are underway to protect key habitats and restore food supplies.
Declining numbers
Many red knot populations have declined in numbers in recent decades. The rufa subspecies which migrates all the way from the Canadian Arctic to Tierra del Fuego has suffered a roughly 75% drop in population since the 1980s.
Their numbers fell from around 100,000 to less than 30,000 birds. This precipitous decline resulted in the rufa red knot being listed as Threatened under the U.S. Endangered Species Act in 2014.
Threats and challenges
Red knots face a variety of threats along their vast migratory routes and in both wintering and breeding areas.
Destruction of stopover and wintering habitats, particularly reclamation of wetlands and tidal flats, has reduced food supplies and shelter. Overharvesting of horseshoe crabs, an essential food source, has also impacted knots.
In the Arctic, climate change is altering tundra breeding habitat. Changing weather patterns may also impact timing of food supplies.
Pollution, disturbance from human recreation, wind farms, and hunting pressure also threaten red knot populations throughout their range.
Conservation actions
Various conservation efforts are underway to stabilize and recover red knot numbers:
– Habitat protection – Creating preserves along migratory routes and wintering areas. Delaware Bay was designated a hemisheric reserve for shorebirds.
– Harvest restrictions – Limiting horseshoe crab harvests to sustainable levels.
– Captive rearing – Small scale captive rearing and release programs to supplement wild populations.
– Monitoring and tracking – Banding, tagging, and tracking birds to monitor populations and distribute information.
– Education – Outreach programs to raise awareness and change harvesting behaviors.
If conservation measures can restore knot food supplies and protect habitats, their populations are expected to rebound thanks to the red knot’s resilience. Continued monitoring and adaptive management will be key.
Interesting Facts about Red Knots
Beyond their amazing migrations, there are many other fascinating things about red knots:
- They get their knot name not from knots of rope, but from King Canute, an ancient Viking king whose name sounded like knot.
- Their scientific name, Calidris canutus, also comes from King Canute.
- Red knots have one of the longest average lifespans of any shorebird, living 15-20 years or more in the wild.
- They eat so much at stopover sites that their organs shrink to accommodate the extra mass – even shrinking their digestive system!
- Red knots undergo dramatic seasonal changes in plumage, molting into bright red and grey breeding plumage.
- They fly in large swirling flocks so dense thatmigration traffic jams can occur at bottleneck sites.
- Some flocks fly so precisely that individual birds make simultaneous turns like a murmuration of starlings.
- Their long-distance flights operate on a finely tuned internal clock and compass system.
- They have specialized feathers on their wings that act like tiny antennae to detect infrasound waves and help guide their migration.
- Climate change impacts are reducing food supplies and causing mismatches between arrival times and food availability.
Conclusion
In summary, red knots are amazing migratory shorebirds that complete some of the longest, most rapid bird migrations on earth. Their unique adaptations allow them to fly vast distances, adapt to dynamic coastal habitats, and congregate in enormous flocks. While some populations are declining, ongoing conservation efforts aim to protect these resilient creatures and their extraordinary migrations into the future. Red knots continue to fascinate both scientists and nature lovers alike.